4.10 gears...not what I expected.

[KILLSHOTS]

Picked up the car yesterday after having the stock 3.45 changed to 4.10 Danas. It appears that I am a victim of my own inflated expectations. After hearing the accolades and reading on this forum a post from a guy who literally said he practically had to "relearn to drive the car" after getting 4.10s, I guess I expected the car to take flight or something. Hmmm, not quite. Yeah, I can tell a small difference but I'd be willing to bet the car is no quicker to a stopwatch, which is kind of a bitter pill to swallow when I just spent $1500 to get "18% more torque to the rear wheels at all engine RPM", according to Marc.

Driving the 2 ratios back to back, I don't feel any 18% torque difference. Not even close. And yes, I did confirm that the stock 3.45s came out of the car. I can say this for sure: if your car is stock or near stock and you're thinking about new gears, DO NOT do anything less than 4.10s. You'd be flushing money down the toilet. Just my 2 cents. :)

[Locobob]

I'm of the opinion that gears shouldn't be looked at as a power adder but rather as a tuning tool to get what you want out of the car. You really only get the extra torque in first gear (provided you have enough tire to hook it up), after that you are just changing shift points.

[mike100]

Obviously gears don't change the torque at the flywheel or affect the power of the engine at all, but what it does do is get you to the sweet spot a little sooner which would be more obvious during acceleration timing, quarter mile runs etc.

6th gear may actually be useful uphill no as well.

[KILLSHOTS]

Obviously gears don't change the torque at the flywheel or affect the power of the engine at all, but what it does do is get you to the sweet spot a little sooner which would be more obvious during acceleration timing, quarter mile runs etc.

6th gear may actually be useful uphill no as well.
Marc says, "18% more torque to the wheels. All of the time!" Of course, gears don't change flywheel HP but gears, by definition, multiply torque and more gear is supposed to provide more torque at the end of the equation. Surprisingly, my car is not even any more tail-happy than before. Extremely disappointing for what's talked about as the "best upgrade ever."

[rhipsher]

Killshot you will feel more of a difference installing a Fidanza flywheel than gears. A light weight flywheel doesn't ad hp either but less rotating mass on the crank is very noticeable. RPM's rise very quickly.

[Bearly Flying]

With stock 3:45' I can spin the tires at will in first gear/ I cannot see how 4:10's would benefit me, it would only light up 2nd gear.

[Dynomite]

"18% more torque to the rear wheels at all engine RPM", according to Marc.

Just my 2 cents. :)

That is a correct statement by Marc. At any specific engine rpm when compared to before and after differential gear change your wheel rpm has gone down and your wheel Torque has gone up (Same wheel Horsepower after drive train losses). This compares to the same engine horsepower output at any given engine RPM (flywheel horsepower) before and after differential gear change.

Now the reason you might not "feel it" is because you have altered your shift points when comparing before and after shift points at specific vehicle speeds. You now have a useful 4th, 5th and 6th gear. When before you could top out the quarter mile in 3rd gear.

Oh...and I can spin my tires in 1st, 2nd, and 3rd gears :D

See Tech Info - LT5 Horsepower and Torque Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660568)

I happen to like stock rear end ratios as I can get that 28mpg cruising in sixth at 70 mph ;)

Killshot you will feel more of a difference installing a Fidanza flywheel than gears. A light weight flywheel doesn't ad hp either but less rotating mass on the crank is very noticeable. RPM's rise very quickly.

See rotating mass discussion and effects on Horsepower Tech Info - L98 Frisbee Horsepower (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660586)

Hi rhipsher :handshak:

[KILLSHOTS]

That is a correct statement by Marc. At any specific engine rpm when compared to before and after differential gear change your wheel rpm has gone down and your wheel Torque has gone up (Same wheel Horsepower after drive train losses). This compares to the same engine horsepower output at any given engine RPM (flywheel horsepower) before and after differential gear change.

Now the reason you might not "feel it" is because you have altered your shift points when comparing before and after shift points at specific vehicle speeds. You now have a useful 4th, 5th and 6th gear. When before you could top out the quarter mile in 3rd gear.

Oh...and I can spin my tires in 1st, 2nd, and 3rd gears :D

See Tech Info - LT5 Horsepower and Torque Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660568)

I happen to like stock rear end ratios as I can get that 28mpg cruising in sixth at 70 mph ;)



See rotating mass discussion and effects on Horsepower Tech Info - L98 Frisbee Horsepower (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660586)

Hi rhipsher :handshak:
Oh no, don't get me wrong: I do NOT doubt Marc. I fully understand the physics of his claim and I know it to be true. My issue is with the EFFECT of the "upgrade". So much was made of it by many that I think I just expected too much. However, going by just the numbers, I think you can understand why I expected a pretty drastic difference. I figured my car (Marc's chip, open exhaust) with stock gears was getting roughly 340 lb/ft of torque to the rear wheels at peak. Multiply that 1.18 and I'm over 400 lb/ft at peak. On paper, that is a DRASTIC difference in twist and I expected a big SOTP effect that I did not realize.

[LGAFF]

porting and exhaust are what I would always go after first....

porting 30-40hp
Exhaust 15-20hp
You could even run the stock exhaust if on a budget, put in an X-pipe and some decent mufflers....

$1000-1200 for 45-60hp and more RPM range

Headers would be next

[LGAFF]

Don yokums 91 made 365rwhp with porting(no port match) and an exhaust system(stock exhaust manifolds). That was not even tuned. So with headers and a tune....390+

[Schrade]

I'm gonna' go the OTHER way here, after I get the pipes hung - 3.45 -> 3.07, since I've lost some top end with the 4L60e. Tach is just a little high @ 70, and it will add up to less wear on longer trips, and less fuel to boot.

I think that 3.07 is my only option here.

I found it interesting to learn that the original track car had a 3.07 installed...

[KILLSHOTS]

porting and exhaust are what I would always go after first....

porting 30-40hp
Exhaust 15-20hp
You could even run the stock exhaust if on a budget, put in an X-pipe and some decent mufflers....

$1000-1200 for 45-60hp and more RPM range

Headers would be next
My exhaust is wide open after the cats. Headers coming soon.

[Locobob]

Marc says, "18% more torque to the wheels. All of the time!" Of course, gears don't change flywheel HP but gears, by definition, multiply torque and more gear is supposed to provide more torque at the end of the equation. Surprisingly, my car is not even any more tail-happy than before. Extremely disappointing for what's talked about as the "best upgrade ever."

Gear to gear at any rpm yes more torque with the 4.10's but.... speed in gears is now different and at certain vehicle speeds the 3.45 car is going to be in a lower gear than the 4.10 car therefore the 3.45 will effectively have more torque in certain speed ranges. Numerically taller gears will not make every car faster in every circumstance, gears should be chosen based on the cars power output, traction, intended purpose and driving style.

[PhillipsLT5]

Would of been nice to see before/after dyno sheets
I still think you made a good move and only will compliment the rest of your future mods
You should now be at aprox 2200RPM @ 75MPH

[Dynomite]

Oh no, don't get me wrong: I do NOT doubt Marc. I fully understand the physics of his claim and I know it to be true. My issue is with the EFFECT of the "upgrade". So much was made of it by many that I think I just expected too much. However, going by just the numbers, I think you can understand why I expected a pretty drastic difference. I figured my car (Marc's chip, open exhaust) with stock gears was getting roughly 340 lb/ft of torque to the rear wheels at peak. Multiply that 1.18 and I'm over 400 lb/ft at peak. On paper, that is a DRASTIC difference in twist and I expected a big SOTP effect that I did not realize.

I understand the expectation given all the talk. But for those that do not understand the physics/math I thought a good time to confuse them more :D

Like LGAFF suggests.....if you want real seat of the pants feel of accomplishment.....ADD HORSEPOWER which is pretty easy on the LT5 :thumbsup:

The 410s do let you get 6th gear into play more often.

[WARP TEN]

I think it is all just a personal thing. I loved getting my 4:10s on my 93 early in its life with me. I felt it really improved my normal around town driving and cruising on the highway. Gears were also one of the first mods I did when I got my 95. To me the car feels quicker. Subjective I realize. I like the usefulness of sixth gear now. It does make the tires spin more but new tires recently helped a lot with that. WARP TEN ran a 12.4/116 at BG this week (admittedly with Marc H driving) and he wasn't power shifting. Overall I am happy with the mod; sorry you don't like them that much. Lots of folks are perfectly happy with stock gears but I am glad I switched. --Bob

[mike100]

If you got 340 rwtq on a dyno in 4th gear you will still get 340rwtq in 4th gear, but at a different speed (lower). There is a trade off- obviously free power isn't created, it is just shifted around by moving the torque curve left or right with respect to rpm, speed, time etc.

[KILLSHOTS]

If you got 340 rwtq on a dyno in 4th gear you will still get 340rwtq in 4th gear, but at a different speed (lower). There is a trade off- obviously free power isn't created, it is just shifted around by moving the torque curve left or right with respect to rpm, speed, time etc.
But how does that square with having "18% more torque to the rear wheels at all engine rpm?" That statement tells me that if I was putting down 340 lb/ft at 4800 rpm with stock gears, then I'm now putting down 401.2 lb/ft at 4800 rpm. Am I oversimplifying or misunderstanding the statement?

[Dynomite]

But how does that square with having "18% more torque to the rear wheels at all engine rpm?" That statement tells me that if I was putting down 340 lb/ft at 4800 rpm with stock gears, then I'm now putting down 401.2 lb/ft at 4800 rpm. Am I oversimplifying or misunderstanding the statement?

You traded wheel spin for wheel torque........same horsepower. Your wheel spin dropped 18%...the guy you were racing just out ran you ;)
18% more torque to the rear wheels at all engine rpm is a true statement. The wheel spin drop at all engine rpm was not mentioned :D

[Schrade]

Just hung up with Psychic Hotline. They said heated discussion on the way yup...

http://www.zr1.net/forum/images/icons/icon10.gif

This statement needs quantification, for starters...
"18% more torque to the rear wheels at all engine rpm?"

And I think a more judicious use of the term "multiply torque" is in order.

[ZZZZZR1]

Chris,

Very interesting that you don't notice a difference with the 4:10's. Most notice a tremendous difference....

Can you get the model # of dana spicer they installed?

Also did they install a speedo correction gear? (did you get it from Marc?)

And if they did install the speedo gear, how accurate is it?

:cheers:

David

[KILLSHOTS]

You traded wheel spin for wheel torque........same horsepower. Your wheel spin dropped 18%...the guy you were racing just out ran you ;)
18% more torque to the rear wheels at all engine rpm is a true statement. The wheel spin drop at all engine rpm was not mentioned :D
So, in reality, an identical car with 4.10 vs 3.45 gears does not necessarily accelerate quicker or harder...it actually accomplishes exactly the same thing, only requiring more engine RPM to do so? Honestly, not trying to be a smartazz here, just trying to understand. Has anybody ever timed a car to 60 or through the 1/4 before and after such a switch? I'd be interested to know because the car doesn't really "feel" any quicker. It definitely revs FASTER but doesn't feel quicker and most surprisingly, doesn't seem to spin the tires more easily. I was hoping to burn those masquerading-as-a-315 Sumitomos to the ground with one burnout!

I've gotten a little more used to it over the weekend and frankly, I sort of like the new "personality" of the car. The upper gears are more usable and the car moves away from a stop more easily, which is great. Again, this has to do with having unrealistic expections, more than anything else. Overall, I'm more surprised with the result than disappointed.

[KILLSHOTS]

Chris,

Very interesting that you don't notice a difference with the 4:10's. Most notice a tremendous difference....

Can you get the model # of dana spicer they installed?

Also did they install a speedo correction gear? (did you get it from Marc?)

And if they did install the speedo gear, how accurate is it?

:cheers:

David
Hey bro!

Yep, I could get you the number of the gearset, I still have the box at home. I also had Marc's correction gears installed. It's different, there's no doubt. It does rev quicker and the upper gears are more useful. As I've said in other replies, I really think this has more to do with unrealistic expectations than anything else. It accelerated hard before and I expected this to increase that sensation but it didn't. It really just feels more high-strung, if that makes sense.

[We Gone]

You should be running out of rpms in 3rd around 100+mph vs 120+mph with 3.45s, I'm around 115mph with 3.73s

[LGAFF]

http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/viewall.html






Geared Up For Speed
Hot Rod did a test of gear ratios and converter sizes (smaller equals higher stall speed) versus engine rpm and quarter-mile times for their June '95 issue. We helped with the testing, so we don't feel too bad about ripping them off and reprinting the numbers here. The car used was a small-block Nova with 26-inch-tall tires. We tried four gear ratios with two TCI converters, and here's what we found:

Same Car....
3.50 gear 13.40@102.59
4.11 gear 13.18@102.81

Read more: http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/#ixzz32C7fPvaZ

[LGAFF]

First let me say, I could take or leave the 4.10s....I would rather have $1500 in motor mods. That being said the 4.10s have:
*Less Bog on the launch
*Better accel from a roll...

I was in my 92 Zr-1(4:09) when two guys in Ducatis kept flying up on the back of the car, then backing down(we were out in the country)....after about 3 three times, the one went to haul *** past me, and when he got up close to the car I punched it....the car pulled with the bike.(it was a smaller Ducati) When we got to a stop they said they were surprised at how well the car pulled compared to the bike....to me with the 3.45 there would have been a "lag"...with the 4.09 its immediate kick in the pants throttle response.

[KILLSHOTS]

http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/viewall.html






Geared Up For Speed
Hot Rod did a test of gear ratios and converter sizes (smaller equals higher stall speed) versus engine rpm and quarter-mile times for their June '95 issue. We helped with the testing, so we don't feel too bad about ripping them off and reprinting the numbers here. The car used was a small-block Nova with 26-inch-tall tires. We tried four gear ratios with two TCI converters, and here's what we found:

Same Car....
3.50 gear 13.40@102.59
4.11 gear 13.18@102.81

Read more: http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/#ixzz32C7fPvaZ
Thanks for this. Yeah, looking at these numbers, I think that this is about the actual performance gain that I would have reasonably expected. But as I've said, in my head, I think I just blew right past expectations that were reasonable. Nobody's fault but mine.

[LGAFF]

I had a guy do a 2.59 to a 3.45 swap on an LT-1 I did head work on...after driving my 3.45 and 4.11 cars and then into the LT-1 it seemed slow....however when he got in it....he was amazed. You are right sometimes its just perspective and in your mind/expectations.

[mike100]

A chassis dyno won't take the gear ratio into account except that some gear selections may have more friction than others. Lets say your engine makes 300 lb/ft of torque and you run it through a 3.08 diff. The axle will see over 900 lb/ft of torque (and of course 3 times slower rpm for a conservation of energy). The chassis dyno won't read 900 lb/ft, it's a separate system with its own diameter and speed calculation. All you get is the engine torque minus the frictional losses (and whatever other fudge factors are in the mix for the dyno).

I always felt individual trans gearing would always be more useful than just the final drive, but that is not too practical in production transmissions. Take a look at the MT-82 trans in the new mustangs... 1st gear is nearly 4:1 and the 1:1 gear is actually 5th (not 4th). That's about 1/2 the reason those new Mustangs scoot so well in the 1/4. I wish the ZF had tighter ratios sometimes.

It is a time-to-distance mod, not so much a seat-of-the-pants mod. I'f I had the budget, I'd do 3.73's myself.

[PhillipsLT5]

.22 @ 1/4 mile, I like it

[Hog]

Stock gearing 3.45

385 lb/ft engine torque/2.66:1 1st gear ratio/3.45:1 rear gear'

385x 2.66x3.45=3533 lb/ft torque at the rear at the halfshafts

4.10 gearing
385 lb/ft torque/2.66:1 1st gear/4.10 ratio

385x2.66x4.10=4198 lb/ft @ the rear halfshafts.

4198/lb/ft3533lb/ft=18.84% increase in torque

We are measuring the actual torque or twist that is seen at the rear wheels, not calculating the torque of the engine.

There would be a measureable difference if before and after 1/4 mile runs were done.

I went from a 3.08 gear to a 4.10 gear and was unimpressed in gains in acceleration during WOT SOTP testing.

[PhillipsLT5]

SOPT = butt dyno

[zrwhat]

I recall when I went to 4:10's in my 91 ZR-1, I shaved .3 tenths off my quarter mile times and the fact that 6th gear could be used more often without downshifting was priceless, before that 6th gear was pretty much worthless unless you were going 70mph on a flat road.

I felt it was a worthwhile change and cheap $ to get there a little faster, I guess I'm one of the few that did notice a big difference with the gear change.

Gibby

[Pete]

http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/viewall.html






Geared Up For Speed
Hot Rod did a test of gear ratios and converter sizes (smaller equals higher stall speed) versus engine rpm and quarter-mile times for their June '95 issue. We helped with the testing, so we don't feel too bad about ripping them off and reprinting the numbers here. The car used was a small-block Nova with 26-inch-tall tires. We tried four gear ratios with two TCI converters, and here's what we found:

Same Car....
3.50 gear 13.40@102.59
4.11 gear 13.18@102.81

Read more: http://www.carcraft.com/techarticles/ccrp_9812_all_about_axle_gears/#ixzz32C7fPvaZ

A bit difference with our manual 6 speed Z's.

I agree money would've been spend better in other mods.

My Z has run 11.04, 11.09, 11.06 with 3.45 gears I install 4.10's thinking I will get a 10 sec pass well that did not work as I thought I got a killer 60ft time and thought h@ll yeah this is it picked up my timeslip 11.10's well anybody wanna guess why, ok i'll tell you had an extra shift.

4.10's are lame and loose big end that's what our cars were made for,top end.
With 3.45 gears I top out 4th at 155-160mph with 4.10's 135mph
and if anyone has shifted into 5th would also know she falls flat on her face in 5th.

4.10's will get you better 60ft times over the 3.45's but with the extra shift takes it right back.

Reinstalled 3.45 back in her and happy again.
Pete

[Bob Eyres]

So Pete, how much better did your 60ft. times get with the 4.10's?

The combination of a better 60ft. time, combined with the advantage of being able to stay in a, (higher), more powerful RPM range throughout the run should add up to a better e.t.
It doesn't seem possible that the brief power shift from 3rd to 4th costs you THAT much.

Is it a possibility that with your high power output, (550+?), and the 4.10 gears, you may need more tire to see the full advantage of this gear ratio?

Your times are phenomenal. But its just hard for me to believe that the best 1/4 mi. e.t. for a high power, high rpm ZR-1 is with a three speed with no torque converter. :confused:

[PhillipsLT5]

A bit difference with our manual 6 speed Z's.

I agree money would've been spend better in other mods.

My Z has run 11.04, 11.09, 11.06 with 3.45 gears I install 4.10's thinking I will get a 10 sec pass well that did not work as I thought I got a killer 60ft time and thought h@ll yeah this is it picked up my timeslip 11.10's well anybody wanna guess why, ok i'll tell you had an extra shift.

4.10's are lame and loose big end that's what our cars were made for,top end.
With 3.45 gears I top out 4th at 155-160mph with 4.10's 135mph
and if anyone has shifted into 5th would also know she falls flat on her face in 5th.

4.10's will get you better 60ft times over the 3.45's but with the extra shift takes it right back.

Reinstalled 3.45 back in her and happy again.
Pete

Shifting into 6th from 5th @ 7200RPM with 4.10's & 422RWHP car really noses over, fighting wind resistance

[USAZR1]

A bit difference with our manual 6 speed Z's.

I agree money would've been spend better in other mods.

My Z has run 11.04, 11.09, 11.06 with 3.45 gears I install 4.10's thinking I will get a 10 sec pass well that did not work as I thought I got a killer 60ft time and thought h@ll yeah this is it picked up my timeslip 11.10's well anybody wanna guess why, ok i'll tell you had an extra shift.

4.10's are lame and loose big end that's what our cars were made for,top end.
With 3.45 gears I top out 4th at 155-160mph with 4.10's 135mph
and if anyone has shifted into 5th would also know she falls flat on her face in 5th.

4.10's will get you better 60ft times over the 3.45's but with the extra shift takes it right back.

Reinstalled 3.45 back in her and happy again.
Pete


If your car is trapping at 129mph and 4.10's are good for 135mph in 4th gear,why are you having to shift into 5th?

[USAZR1]

It really noses over from 5th to 6th,with 3.45's also. I really liked the 155mph 4th gear w/3.45's but I find the 4.10's are a much more useful ratio,overall.
Our car will see a bunch more 0-120mph blasts than it ever will to 150+. If top end blasts are your thing,3.45's or even 3.07's are the way to go.

[Pete]

Here's what i think.
That auto car for example, lets say peak power is at 5500 rpm with the 3.50 gears it would finish the 1/4 at 4700 rpm with the 4.11 it would finish at 5500 this is the reason for the much better ET's.

My Z peak power 6900rpm with 3.45 i finish in 3rd gear at about 7400 rpm
With 4.10's i finish in 4th at 6800 below my power peak so either i god with 4.33's or 4.50's
My Z looses about 15hp from peak (6900) to 7400rpm so not much loss.

Also i did not mean going into 6th i meant going into 5th i know you don't feel it much but trust me car does not pull as hard in 5th if you shift her at 7k rpm it drops way below peak power down to 5200 rpm what you have to do is run her to 74-7500rpm just to get her closer to peak power going into 5th.

I went from 1.74 60ft to 1.59 you would think 1.5 at 60 foot would get me 2-3 tenths i can't shift that fast so i loose it at the extra shift even if i got 11.00 it still did nothing for me.

Pete

[USAZR1]

Here's what i think.
That auto car for example, lets say peak power is at 5500 rpm with the 3.50 gears it would finish the 1/4 at 4700 rpm with the 4.11 it would finish at 5500 this is the reason for the much better ET's.
My Z peak power 6900rpm with 3.45 i finish in 3rd gear at about 7400 rpm
With 4.10's i finish in 4th at 6800 below my power peak so either i god with 4.33's or 4.50's
My Z looses about 15hp from peak (6900) to 7400rpm so not much loss.
I went from 1.74 60ft to 1.59 you would think 1.5 at 60 foot would get me 2-3 tenths i can't shift that fast so i loose it at the extra shift even if i got 11.00 it still did nothing for me.
Pete


So,you're going through the lights in 3rd gear,not 4th? If your stock displacement LT5 makes peak at 6,900,I agree a 4.30 cog might work better than a 4.10 for your combo. A 4.56 would probably be too much gear.

[Paul Workman]

From another perspective - the recent Mountain Run some of us did last week:

Shortly before doing the run, I had a chance to experience Brett's 350 LT5 thru (4.10s). There is NO QUESTION the seat of the pants could feel the increase in punch over my 3.45 cog (allowing a little to maybe an extra ≈ 30 hp for the bigger cams in Brett's car).

But, as others have said, 6th gear in the mountains was pretty much useless, except above 70 on flat stretches. I believe a bigger ratio would have been useful in the hilly terrain. Even with a lot of the time spent in 2nd and 3rd gears and sustaining 3000 to 4000 rpm** over some stretches of curves, there were times when I was dropping into 1st (remember altitude plays a role too). A little more "dig" would have been welcome; it would have put the LT5 into its sweet spot - above 5000 rpm+ more easily.

**From the perspective of lingering in the 3000-4000 rpm range, it occurred to me that would put an LSx or perhaps even the new LT1 (C7 motor) right in their sweet (torque) spot - assuming at or close to the same rear gear ratio. Those LSx motors' (torque) peaks earlier (at less rpm) compared to the LT5, and in that particular application they would out-pull the LT5s unless the ZR-1 had something like the 4.10 ratio to bring the LT5 rpm into its prime torque vs. rpm range too.

That said, the results from last year's running of the 1/2 mile in Monee clearly showed where the LT5s shine. As Pete mentioned, the LT5s are obviously long-legged; pretty much dominating LS motors at that event in spite of the LS boys having a cubic inch advantage. (limited to NA motors, that is). I would attribute that to the fact that venue favors motors with peak hp in the high rpm range. The 3.45 geared Zs did very well for themselves! But, there were reports from the 4.10 geared LT5 guys that in that venue the cars would nose over when hitting 5th gear (somewhere above 120 mph).

So, the 4.10s in any one gear will increase torque at the wheels, and thus acceleration - in that gear, taken on the whole in a distance/speed venue vs. a hilly/twisty course (with altitude tossed in) ether the 3.45 or the 4.10s have their special place.

For now, I will admit the 4.10s are fun, especially on the street. But, taken on the whole - the extra shift in the 1/4 mile mitigates most of the advantage of the 4.10 gear for the ZR-1; at least for that venue (maybe if one power shifts, the extra shift could maybe be overcome to result in favor of the 4.10s...but not with MY ZF transmission - thank you very much!!). AND, hitting the 1/2 mile at the top of 4th with the 3.45 - is about as ideal as you can get for that application.

The 3.45s are evidently pretty good "all round" for speed/distance up to 1/2 mile contests (sans possibly power shifting). However, for mountain thrills...the 4.10s would have been VERY nice to have. It boils down to the venue, I recon. Too bad we don't have quick-change rear differentials like we had in modified stock (dirt track) racing. In under 20 minutes you could change the ratio to fit the speed/rpm equation for that track.

I'm thinking I'd love the 4.10s for street and cruising the twisties. But, for speed/distance contests, the 3.45s - up to 1/2 mile - it's pretty hard to beat the versatility. Even if one goes with a compromise between 3.45 and 4.10 (or 4.30s?) that gear too would favor certain venues at the expense of some other. Decisions, decisions....:( Maybe the answer is to have multiple Zs, each with different ratios and simply choose the Z that fits the situation. Yeah... I LIKE that idea!

[JFFerner]

It seems too much might not be enough, meaning the extra shift into fourth gear is offsetting any positive impact of torque multiplication when using the 4.10 ratio. Why not use a 3.73 ratio which will give a smaller torque multiplying advantage, but will keep you in third gear in the 7000 rpm range through the traps.
And so it goes....Jim

[KILLSHOTS]

So, I've had these new gears for a week now, and I am ready to amend my initial comments. Those comments, as I've said earlier, were based upon overly-inflated expectations that had gone unrealized. I also want to reiterate that I know Marc's "18% more torque" claim is 100% true. I NEVER doubted Marc and never wanted to give the impression that I doubted him and if I did that, I apologize to all, and especially Marc. My point was that I didn't FEEL 18% more torque, not that I thought it wasn't really there.

1) The car moves away from a stop much more easily and requires less slipping of the clutch. It gives the impression of a smaller, lighter car.

2) As Marc says, it does get to the "meat" of the power band more quickly, which is great.

3) The upper gears are definitely more useful.

To anyone considering this gear change, my advice would be to consider it more of a "driveability" upgrade than a "performance" upgrade. In my opinion, the overall character of the LT5 does seem to work a little better with the shorter gearing, which lends credence to the claim that the engineers originally designed this drivetrain with these gears in mind. Just don't expect the thing to take flight the first time you hammer it, like I did!

[Paul Workman]

It seems too much might not be enough, meaning the extra shift into fourth gear is offsetting any positive impact of torque multiplication when using the 4.10 ratio. Why not use a 3.73 ratio which will give a smaller torque multiplying advantage, but will keep you in third gear in the 7000 rpm range through the traps.
And so it goes....Jim

Yeah... That's where hp elbows its way into the discussion. For example, I (and several others here in FBI country) are @ or above 500 hp. I go through the traps at 121 mph and just as my shift light comes on (at 7100 rpm). A 3.73 would require a shift to 4th before the traps.

However, a 3.73 may be correct for a stock motor. When mine was stock, I ran 112 mph in the traps at about 6600. A 3.73 might be a good stock motor ratio.

This echos back to what Lee says - that being power mods are what makes the big difference, at least in the ZR-1/ 1/4 mile performance.

[Pete]

Here's another food for thought.
Two ZR-1's run same 1/4 MPH one has 4.10's the other has stock 3.45.
Guess which is winning from a 40-50-60-70-80-90-100 roll.

Pete

[5ABI VT]

Im not a fan of steep gears myself. I have a little explanation that I tell people that Includes a Sumo wrestler vs Chuck Norris if anyone would like to hear it lol.

Trying to be as short as I can.. but to me gears are great if you are running 1/4 mile and 'quickness' means everything to you. If you can hook first gear, that steep ratio will help launch way harder and you will shave a noticeable amount off your e.t. For all other speeds besides launch gears are useless. The way I see it comparing 3rd gear with 4.09s and 2nd gear with stock gears is more relevant. Look at the speeds of those two final drives and you will see the multiplication difference and at the MPH that it occurs. People fail to take into consideration that yes gears multiply torque, but you are going slower in those gears. So 3rd feels faster.. but now you are only going the same speed as 2nd used to get to. SO really is your new faster 3rd much better than the old 2nd? that's how I see it.

Also the zf is a 5 speed + massive overdrive. reverse shares the same synchro as 6th so using 6th to accelerate [-X. Don't ask me how I know.

On my LT4 that spun 8k I dropped from 4.30 which was a waste of tires gear to 4.09. Which effectively made my trans a 3 speed (1-2 were useless) and went down to a 3.73. WIth the target troque being so high it effectively killed torque in the low range which was my goal and helped hook 1st gear on street tires. I also trapped 128 mph on low profile 19s at 44 psi on a road race suspension. Most races were well over in 4th anyways which was perfect since it topped out around 275 ish km/hr. Let the torque do the work which is what I like to say :)

Theres a reason the c6 z06 went numerically lower with a final drive. Torque. let the torque do the work. The viper is another example. It has a numerically low gear ratio (1st gen anyways) why? because its a truck motor and it doesn't like to rev. give it less gear and let the torque do the work. Its no secret viper owners got brainwashed by all the gears bs and put 4.10s and went to the track and went slower. In my opinion its one of the biggest mistakes people make with high hp/torque cars and why some dyno queens just cant make the mph and times on the road.

[batchman]

With 4.10's i finish in 4th at 6800 below my power peak so either i god with 4.33's or 4.50's

This echoes what a lot of folks homed in on with the 4.6 DOHC Cobras. A 3.73 or 4.10 was kind of considered what should have been the stock gear (3.27s in my year) but for 1/4mi work the conclusion was 4.30s or 4.56s - the mantra became "Don't fear the gear!". Apples and Oranges sure, but the curves, character, peaks and limits are similar. Note I did not say similar NA power!

Please note the above is secondhand but as a part of that community I watched a lot of efforts reaching that conclusion. I was autocrossing in stock class with my '99 so a gear change was something I could only lust after.

Now with the red car in *SP class I can, and hope to (someday) go to the 3.54. A lot of work for not much gain but still it is a gain, and that's racin'.

Cheers,
- Jeff

[Hog]

Im not a fan of steep gears myself. I have a little explanation that I tell people that Includes a Sumo wrestler vs Chuck Norris if anyone would like to hear it lol.

Trying to be as short as I can.. but to me gears are great if you are running 1/4 mile and 'quickness' means everything to you. If you can hook first gear, that steep ratio will help launch way harder and you will shave a noticeable amount off your e.t. For all other speeds besides launch gears are useless. The way I see it comparing 3rd gear with 4.09s and 2nd gear with stock gears is more relevant. Look at the speeds of those two final drives and you will see the multiplication difference and at the MPH that it occurs. People fail to take into consideration that yes gears multiply torque, but you are going slower in those gears. So 3rd feels faster.. but now you are only going the same speed as 2nd used to get to. SO really is your new faster 3rd much better than the old 2nd? that's how I see it.

Also the zf is a 5 speed + massive overdrive. reverse shares the same synchro as 6th so using 6th to accelerate [-X. Don't ask me how I know.

On my LT4 that spun 8k I dropped from 4.30 which was a waste of tires gear to 4.09. Which effectively made my trans a 3 speed (1-2 were useless) and went down to a 3.73. WIth the target troque being so high it effectively killed torque in the low range which was my goal and helped hook 1st gear on street tires. I also trapped 128 mph on low profile 19s at 44 psi on a road race suspension. Most races were well over in 4th anyways which was perfect since it topped out around 275 ish km/hr. Let the torque do the work which is what I like to say :)

Theres a reason the c6 z06 went numerically lower with a final drive. Torque. let the torque do the work. The viper is another example. It has a numerically low gear ratio (1st gen anyways) why? because its a truck motor and it doesn't like to rev. give it less gear and let the torque do the work. Its no secret viper owners got brainwashed by all the gears bs and put 4.10s and went to the track and went slower. In my opinion its one of the biggest mistakes people make with high hp/torque cars and why some dyno queens just cant make the mph and times on the road.
Curious, what PCM were you using on your 8000rpm LT4? Aftermarket? Stockers shut down after 7300-7400rpm.

The other reasons why the ZO6 and Viper went with a lower rear gear, was to be able to reach their top speeds with teh available transmissions.

[Hog]

Here's another food for thought.
Two ZR-1's run same 1/4 MPH one has 4.10's the other has stock 3.45.
Guess which is winning from a 40-50-60-70-80-90-100 roll.

Pete

All else equal, the 3.45 geared car will win from a roll. Unless you are rolling on in 5th gear.

[KILLSHOTS]

If I had no idea what a ZR-1 was, and I was to go back and read this thread in its entirety, I would conclude that the ZR-1 serves one primary purpose: a 1/4 mile drag car. Virtually every poster mentions, above all else, 1/4 mile time, rpm, etc. Granted, I was curious as to whether any back-to-back acceleration comparisons had been done with the 2 gearsets, but I didn't change gears to ensure that I went through the trap at a specific rpm. That's just me, though.

Not saying there's anything wrong with it at all; I'm just kind of surprised that rpm in gears seems to be the most important factor in a potential gear swap. Just my observation.

Have a great holiday weekend, all! :cheers:

[XfireZ51]

I'm using 3.73s BUT I also have taller 19" wheels which effectively makes my gearing ~ a 3.50. Lgaff and myself had nearly identical setup a few years ago w the exception of gearing. He had a 4.10 in his 92 red, I had 3.45s w 92 aqua. Bot were top end mods and had the same headers, Watsons. Lee was usually faster by about .3-.4 but our trap speeds were within 100ths of a mph. He would beat me to the 1/8th w a higher mph but by the end, I would be gaining on him. Pretty sure that after the 1/4, I would have overtaken him. Just some anecdotal evidence.

[5ABI VT]

I'm using 3.73s BUT I also have taller 19" wheels which effectively makes my gearing ~ a 3.50. Lgaff and myself had nearly identical setup a few years ago w the exception of gearing. He had a 4.10 in his 92 red, I had 3.45s w 92 aqua. Bot were top end mods and had the same headers, Watsons. Lee was usually faster by about .3-.4 but our trap speeds were within 100ths of a mph. He would beat me to the 1/8th w a higher mph but by the end, I would be gaining on him. Pretty sure that after the 1/4, I would have overtaken him. Just some anecdotal evidence.


Which in my eyes shows the only advantage is having a shorter first gear. If you can take advantage of the increased torque at the tire in first it will get you ahead and then it's an even race until the shorter geared car hits 5th which is pretty much an overdrive then the stick geared car should catch and usually the race is well over before needing to go to 6th.

I ran a similar race when my 93 lt1 was bolt ons with 4.10s. When I started in 2nd gear from a 15 mph roll when the stock geared car was in 1st.. Were were pretty much neck and neck until I hit 5th. I would pull slightly and then lose it on the shift and repeated in every gear. If I launched hard in 1st I kept that advantage (about a car and a half) until I hit 5th where he would catch and pull slightly ahead before he hit 5th.

Personally I hated the gears back then. It was fun at first until I realized for all that extra push, I was moving at a slower speed in each gear. I started to miss that nice long uninterrupted pull.

[USAZR1]

All else equal, the 3.45 geared car will win from a roll. Unless you are rolling on in 5th gear.


No,it won't. From 60-120mph,all else being equal,a mildly modified ZR-1 w/4.10's will dust one w/3.45's. The car with lower gearing will pull harder to redline every time

[5ABI VT]

No,it won't. From 60-120mph,all else being equal,a mildly modified ZR-1 w/4.10's will dust one w/3.45's. The car with lower gearing will pull harder to redline every time

I don't believe that's the case . It pulls harder to redline but you're shifting faster and the speed at which gear tops out at is much less. What I'm trying to say is assuming the stock geared car is in 2nd and the 4.10 car is in 3rd.. How is the 4.10 car accelerating harder ?

Final drive in 2nd gear with stock gears is : 1.8x3.45 =6.21
Final drive in 3rd gear with 410 gears is : 1.29x4.10 = 5.28

Speed for stock gear car is 60 mph and 4900 rpms. If you ask me that's right in the sweet spot

Speed for the 4.10 car at 60 mph is 5800 rpms in 2nd and if using second it has a more favorable final drive for the split second it takes to hit the limiter and then will lose that momentum in the shift to 3rd where the final drive favors the stock geared car again. At 74 mph in 3rd (assuming shift at 7200) the 4.10 car will be at a lower final drive than the stock geared car until the stock geared car needs to shift at 90 mph at which point the advantage goes back to the 4.10 car.

Confusing but it's back and forth depending on who's in the sweet spot if were talking roll on races . The only advantage in final drive a 4.10 car has is 1st gear because that is the lowest gear that is possible to use. If a 4.10 car has slicks and dumps at 7200 and hooks and launches a full 2 car lengths ahead.. It will maintain that because after first gear and shifting into second the final drive advantage goes back to the stock rear car that is still in 1st. And so it goes back and forth .. Get it ? THAT is why gears show a e.t difference but no difference in mph.


So my conclusion is .. 4.10 gears are great for a 1 gear advantage only. Off the line if you can hook. That's it. :)


The most common mistake I see people do is compare the SAME gear roll ons from a rear gear swap vs stock. That's not really fair to do because the speeds and ranges of the gears has now changed somewhat . In many cases the stock gear car should be in a lower gear where the final drive may be in it's favor for a brief period and pass it back and forth.

[XfireZ51]

Lee was at top of 4th while I was topping out in 3rd at the end of the 1/4. I was gaining on him in the last 300'. He typically would have a higher 1/8th trap by about 1-2mph. But by the end of the 1/4, our Mph was nearly identical. The next shift would have reversed positions. We're talking about somewhere around 118mph. And frankly, Lee is a better driver than I am.

[USAZR1]

I don't believe that's the case . It pulls harder to redline but you're shifting faster and the speed at which gear tops out at is much less. What I'm trying to say is assuming the stock geared car is in 2nd and the 4.10 car is in 3rd.. How is the 4.10 car accelerating harder ?

Final drive in 2nd gear with stock gears is : 1.8x3.45 =6.21
Final drive in 3rd gear with 410 gears is : 1.29x4.10 = 5.28

Speed for stock gear car is 60 mph and 4900 rpms. If you ask me that's right in the sweet spot

Speed for the 4.10 car at 60 mph is 5800 rpms in 2nd and if using second it has a more favorable final drive for the split second it takes to hit the limiter and then will lose that momentum in the shift to 3rd where the final drive favors the stock geared car again. At 74 mph in 3rd (assuming shift at 7200) the 4.10 car will be at a lower final drive than the stock geared car until the stock geared car needs to shift at 90 mph at which point the advantage goes back to the 4.10 car.

Confusing but it's back and forth depending on who's in the sweet spot if were talking roll on races . The only advantage in final drive a 4.10 car has is 1st gear because that is the lowest gear that is possible to use. If a 4.10 car has slicks and dumps at 7200 and hooks and launches a full 2 car lengths ahead.. It will maintain that because after first gear and shifting into second the final drive advantage goes back to the stock rear car that is still in 1st. And so it goes back and forth .. Get it ? THAT is why gears show a e.t difference but no difference in mph.


So my conclusion is .. 4.10 gears are great for a 1 gear advantage only. Off the line if you can hook. That's it. :)


The most common mistake I see people do is compare the SAME gear roll ons from a rear gear swap vs stock. That's not really fair to do because the speeds and ranges of the gears has now changed somewhat . In many cases the stock gear car should be in a lower gear where the final drive may be in it's favor for a brief period and pass it back and forth.


Michael,I said "all else being equal",did I not? How is one car being in 3rd gear and one in 4th, equal? Try a roll-on with both cars in the same gear,especially in 3rd gear or higher as that will take tire spin out of the equation,and get back to me.

Reading your last paragraph made me chuckle. How is all else equal not being fair?

You don't believe it to be the case? I have done 3rd,4th,and 5th gear roll-ons against other ZR-1's and did find it to be the case.

18% increase in torque doesn't lie,does it?

[USAZR1]

Lee was at top of 4th while I was topping out in 3rd at the end of the 1/4. I was gaining on him in the last 300'. He typically would have a higher 1/8th trap by about 1-2mph. But by the end of the 1/4, our Mph was nearly identical. The next shift would have reversed positions. We're talking about somewhere around 118mph. And frankly, Lee is a better driver than I am.

Sure,you were starting to reel him in. His LT5 was probably starting to run out of breath in 4th gear with those 4.10's. Whereas,at 120mph,your car with the 3.73's was still hitting its stride.
But,you didn't catch him,did you?

I won't argue the point that 3.45's aren't an excellent cog for top-end blasts over 120mph. But,I ask the question once again: How many times a year does your ZR-1 see speeds way over 120mph? Probably,not that often. How often do you find yourself driving down the expressway in 5th gear,instead of 6th? When my car still had the 3.45's,I caught myself doing it quite often. To be perfectly honest,I wouldn't mind if our 94 had 3.45 cogs because the Texas speed limits are 75mph or even higher.
But,I still prefer a little more acceleration over a little more top end. Different strokes for different folks,,

[Paul Workman]

No,it won't. From 60-120mph,all else being equal,a mildly modified ZR-1 w/4.10's will dust one w/3.45's. The car with lower gearing will pull harder to redline every time

Well, 18% torque increase for any rpm is correct, but it is a bit simplistic: The torque curve is not flat across the rpm range, and speed at the top of every gear is going to be 18% less for any give rpm. The combination of rising and falling torque curves over rpm and the fact of some loss in speed/time for each shift apparently tends to mitigate a substantial amount of the advantage of the 4.10s for the ZR-1 in the 1/4 mile - or so it seems from observation.

And, to Dom's point, Those that ran the 1/2 mile drags in Monee last year, the 3.45 geared cars really featured the LT5's strong suit - faring much better at 140+ mph in 4th than that reported by the 4.10 guys - having to shift to 5th and experiencing the cars acceleration "dive" when they did so.

What is starting to emerge, sans any formal analysis here so far, is the 4.10s may not be big enough for either the 1/4 or even the 1/2 mile contest to make a clear, indisputable advantage over the stock 3.45 "cog", but only in part due to the extra shift. In both cases ending in 4th in the "quarter" or 5th in the 1/2, the LT5 is not at peak power. So, less than peak power in the trap PLUS the extra shift eats up most of the torque advantage of the 4.10 in either contest: just NOT quite enough gear. Something like a 4.3:1 gear might fix that, me thinks.

I like 5ABI VT's description of the "back and forth" advantage when comparing the two (3.45 vs. the4.10) in the quarter mile contest (and perhaps the 1/2 mile too). Not so clearly cut and dried as comparing gear ratios alone would suggest.

Interesting discussion.:)

[USAZR1]

Well, 18% torque increase for any rpm is correct, but it is a bit simplistic: The torque curve is not flat across the rpm range, and speed at the top of every gear is going to be 18% less for any give rpm. The combination of rising and falling torque curves over rpm and the fact of some loss in speed/time for each shift apparently tends to mitigate a substantial amount of the advantage of the 4.10s for the ZR-1 in the 1/4 mile - or so it seems from observation.

And, to Dom's point, Those that ran the 1/2 mile drags in Monee last year, the 3.45 geared cars really featured the LT5's strong suit - faring much better at 140+ mph in 4th than that reported by the 4.10 guys - having to shift to 5th and experiencing the cars acceleration "dive" when they did so.

What is starting to emerge, sans any formal analysis here so far, is the 4.10s may not be big enough for either the 1/4 or even the 1/2 mile contest to make a clear, indisputable advantage over the stock 3.45 "cog", but only in part due to the extra shift. In both cases ending in 4th in the "quarter" or 5th in the 1/2, the LT5 is not at peak power. So, less than peak power in the trap PLUS the extra shift eats up most of the torque advantage of the 4.10 in either contest: just NOT quite enough gear. Something like a 4.3:1 gear might fix that, me thinks.

I like 5ABI VT's description of the "back and forth" advantage when comparing the two (3.45 vs. the4.10) in the quarter mile contest (and perhaps the 1/2 mile too). Not so clearly cut and dried as comparing gear ratios alone would suggest.

Interesting discussion.:)


I agree that is overly simplistic,Paul. Nothing is ever cut & dried. Just having fun with Michael. He's a good poster and has interesting opinions.

I also agree that 4.10's would not be my first choice for 1/2 mile drags or especially full mile runs. With those new racing venues,4.10's aren't as big a deal as they used to be when I owned my first two ZR-1's over ten years ago.

[Hog]

No,it won't. From 60-120mph,all else being equal,a mildly modified ZR-1 w/4.10's will dust one w/3.45's. The car with lower gearing will pull harder to redline every time

Modified or not, the facts are the same. The engine will accelerate to red line quicker with lower gearing but will the car will not accelerate harder. F=MA

You dont want lower gearing for roll racing(dead stop drag racing is different), nor do you want to roll race a manual trans against an auto trans, all else equal.

You cant directly compare 2 cars, you have to test the same car, then make changes and retest. All else is benchracing(which can also be enjoyable).

[USAZR1]

Modified or not, the facts are the same. The engine will accelerate to red line quicker with lower gearing but will the car will not accelerate harder. F=MA

You can't directly compare 2 cars, you have to test the same car, then make changes and retest. All else is benchracing(which can also be enjoyable).

"The engine will accelerate to red line quicker with lower gearing but the car will not accelerate harder." Someone please explain this statement to me because it just doesn't make any sense. :neutral:

That's all I thought we were doing here,,benchracing and having fun. :):)

[Paul Workman]

Sure,you were starting to reel him in. His LT5 was probably starting to run out of breath in 4th gear with those 4.10's. Whereas,at 120mph,your car with the 3.73's was still hitting its stride.
But,you didn't catch him,did you?

Minor correction: 120 mph with stock wheels the ZR-1 will be pretty close to 7000 rpm in 3rd gear, but we're talking a modded LT5 at those 1/4 mile speed levels (above 500 hp). A stock LT5 would be more likely at 110 mph at the top of 3rd gear with 3.73s, actually.;)

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZF6MPH345vs410gearratio-Haibeck_zps837f03ef.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/ZF6MPH345vs410gearratio-Haibeck_zps837f03ef.jpg.html)

... But,I ask the question once again: How many times a year does your ZR-1 see speeds way over 120mph?...

Uh...more often than you might think!:dancing Gears are dandy, but horsepower ends the acceleration vs. top end compromise!

[Bob Eyres]

My Z peak power 6900rpm with 3.45 i finish in 3rd gear at about 7400 rpm
With 4.10's i finish in 4th at 6800 below my power peak so either i god with 4.33's or 4.50's
My Z looses about 15hp from peak (6900) to 7400rpm so not much loss.

I went from 1.74 60ft to 1.59 you would think 1.5 at 60 foot would get me 2-3 tenths i can't shift that fast so i loose it at the extra shift even if i got 11.00 it still did nothing for me.

Pete

This bench racing is fun isn't it? It saves on parts :-D

I still think Pete could cut quicker times with 4.30's, or 4.56's (depending on tire). As he says, the 4.10's got him a 1.59 60ft. time, that's phenomenal, and a big advantage in the Qtr.

A .15 advantage in the first 60ft. is several car lengths in the traps. You don't lose that much, (maybe a fender), during the 3-4 shift.

That tells me that the 4.10's are not too much gear, but not enough. The reason his times got slower is not the third to fourth shift, but because he wasn't peaking out to 7,400-7,500 in the traps. The trick is getting the great launch AND peaking at the right rpm in the traps.

I see the stock gear as a disadvantage at launch. If he cuts 1.74 60 ft time with 550+h.p. and a stock gear, and I cut a 1.76 with 4.10's and a stock motor. How is that using all that horsepower that he's spent so much time and effort building? Just sayin' :confused:

More gear, more tire:eek:

[Hog]

"The engine will accelerate to red line quicker with lower gearing but the car will not accelerate harder." Someone please explain this statement to me because it just doesn't make any sense. :neutral:

That's all I thought we were doing here,,benchracing and having fun. :):)

Explaination:Just because the engine is revving to redline quicker(less time) doesnt necessarily mean that the car is also accelerating quicker. Think of a "block and tackle" a single pulley will be able to lift LESS weight, than 3 pulleys. But the single pulley will lift its weight by winding up less rope than the 3 pulley system. Though the 3 pulley system does move more weight, it also requires many more times the amount of rope to lift any weight. The single pulley being analogous to stock rear gears(3.45), and 3 pulleys being analogous to lower gearing(4.56).


Yes, bench racing is what we are doing here, and it's fun, so long we bring the Scope.

[Bob Eyres]

I don't agree. You don't have to go to a block and pulley analogy to explain it. Just look at 60ft. times.

If a ZR-1 cuts a 1.50 60ft., and another cuts a 1.60, who's accelerating harder?

The ZR-1 with 4.10's will cut a better 60ft. every time. All other things being equal.

[XfireZ51]

I was told by someone who raced SuperStock for many years that a smaller gear absorbs more energy than a taller gear and so wheel spin is easier to control.
You need more rpm to turn the wheel once w a smaller gear.

[Bob Eyres]

The shorter gear actually allows you to apply more rpm, thereby more torque to the wheels at launch. Gears don't literally absorb energy.

It's really about leverage. Short gears give more leverage, but require more rpm to do it. The ZR-1 develops it's power at a higher rpm, therefore requires shorter gears.

[Hog]

Someone mentioned that a 4.10 gear isnt worth it for a 1/4 mile run based on the addition of a shift, and not trapping at peak power.
Then someone mentioned that the 4.10 may not have neen enough gear, perhaps a 4.30 or 4.56 is in order?
I would agree with that. So long as you can hook, your 60ft will decrease which will help 1/4 mile times. This is true because of the extra torque applied at launch, extra Force. This decreases as you move off the line as the engine approaches and passes peak power.

I had a drag vehicle that made peak power at 4800rpm. With 3.08 gears it would trap the 1/4 mile at 5500rpm in 2nd gear. Swapping to 4.10 gears allowed for a trap rpm of 5000rpm in 3rd gear. In this experience 60ft et dropped, 1/4 mile et dropped, but 1/4 mile speed also dropped 3-4mph.

Torque=Rotational force at any moment
Power=(Torque(lb/ft) x rpm)/5252
Acceleration=Change in velocity over time
Work=force which acts on an object which results in a displacement, if you push on a car with a force of 100 pounds, you are expending energy through your muscylar effort, but if the car doesnt move, no work has been accomplished Work=Force x Displacement
Mass=Vehicle weight

We also have to remember that when we shift from 4th(1:1) to 5th(0.75:1), or lets say the driveshaft rpm is 7,500rpm in 4th gear with a 7500 engine rpm in 4th, the same 7,500engine rpm becomes 10,000 driveshaft rpm, in 6th 0.50:1 would be 15,000rpm.

Some of the newer transmissions (TR6060) have less split from 4th to 5th, which helps reduce that nose-over feeling that some experience when shifting to OD.
Engine torque=400lb/ft
Rear Gear 3.45:1
Engine Torque x trans ratio x rear gear=torque applied to ground
400x2.66x3.45 =3671lb/ft
400x1.80x3.45-2484 lb/ft
400x1.30x3.45=1794 lb/ft
400x1.00x3.45=1380 lb/ft
400x0.75x3.45=1035 lb/ft
400x0.49x3.45=676 lb/ft

SO throwing a 4-5 upshift losses 345 lb/ft of applied torque combined with the fact that at this speed aerodynamic forces are increasing, thus adding to negative acceleration.

Fascinating discussion, so many variables. With the extended rpm potential of the LT5 conventionally agressive gearing, isnt so agressive when used with the LT5.

[Schrade]

Just hung up with Psychic Hotline. They said heated discussion on the way yup...

http://www.zr1.net/forum/images/icons/icon10.gif

This statement needs quantification, for starters...

"18% more torque to the rear wheels at all engine rpm?"

And I think a more judicious use of the term "multiply torque" is in order.

http://s1.e46fanatics.com/forum/images/smilies/lockd.gif

[Hog]

I don't agree. You don't have to go to a block and pulley analogy to explain it. Just look at 60ft. times.

If a ZR-1 cuts a 1.50 60ft., and another cuts a 1.60, who's accelerating harder?

The ZR-1 with 4.10's will cut a better 60ft. every time. All other things being equal.
I had to go to a block and tackle as the other gentleman didnt understand.
My point was, that just because your tach reaches 7500rpm quickly, doesnt mean that your speedo is accelerating as quickly.

I agree with your drag scenario a car cuts a 1.50 60ft, and another hits a 1.6 60ft. The 1.5 60ft is accelerating harder.

I also agree, a 4.10 geared ZR-1 will cut better short times(60 ft) than a higher geared ZR-1, all else equal.

Now I ask you this, in your scenario ZR-1 #1 cuts a 1.50 60ft with its 4.10 gear, and ZR-1 #2 cuts a 1.60ft short time with its 3.45 gear.

Which ZR-1 will trap with the higher Speed MPH? All else equal.

[Bob Eyres]

The short, smart*ss answer is, It doesn't matter. Because the one with the best e.t. wins.
I don't pay much attention to trap speed because I dont' care how fast you're going in the traps if you're behind me. :p

With the 4.10 gears I trap 117+ with a stock motor and boltons. That's a whole lot better than my early efforts with stock gears that trapped a best of 110-111mph.

The short gears allow you to keep the engine up in it's most powerful rev range for more of the time during the race. Someone running the quarter in two or three gears spends more time climbing up to max power, as in your example. That's another way to explain the advantage of short gears.

Of course, those with a torque converter overcome that disadvantage in another way. But that's a whole other discussion.

[Hog]

The short, smart*ss answer is, It doesn't matter. Because the one with the best e.t. wins.
I don't pay much attention to trap speed because I dont' care how fast you're going in the traps if you're behind me. :p

With the 4.10 gears I trap 117+ with a stock motor and boltons. That's a whole lot better than my early efforts with stock gears that trapped a best of 110-111mph.

The short gears allow you to keep the engine up in it's most powerful rev range for more of the time during the race. Someone running the quarter in two or three gears spends more time climbing up to max power, as in your example. That's another way to explain the advantage of short gears.

Of course, those with a torque converter overcome that disadvantage in another way. But that's a whole other discussion.
Tee-hee, reason I asked about mph as it is the indicator of power, moreso than ET.

I've noticed that sometimes in a 1/4 mile drag situation, that with lower rear gears, that while ET can increase, trap mph can decrease, all else equal.
If I am reading correctly, you have been experiencing highr MPH trap speed with your lower gearing? Interesting.

xxxxxxxxxxxxxxxxxxxxxxxxxxx
I just ran some numbers:
7000rpm/3.45 gear/25.5"tire 1:1 4th gear gives 154mph
7000rpm/3.73/25.5"/4th gear gives 142mph
7000rpm/4.10.25.5"/4th gear is 130mph
7000rpm/4.30/25.5/4th gear gives 123mph
7000rpm/4.56/25.5/4th gear is 116mph
7000rpm/4.88/25.5/4th gear is 109mph
7000rpm/5.13/25.5/4th gear is 104mph, **** to 5th and 138mph is attaiable at 700rpm, then shift again into 6th gear and 211mph is attainable at 7000rpm. 5.13's in 6th gear at 70mph would be revving 2325rpm. 7000rpm in 1st gear with 5.13's gives you 39mph.

Looks like the amount of power the engine makes, will affect just what gearing you would need to run, IF the goal is best 1/4 mile ET.

The lower the rear gear (higher number) also helps to reduce driveshaft/trans/clutch/engine loading. Everything after, starting with the ring gear to the tires would experience increased loading.

[USAZR1]

Tee-hee, reason I asked about mph as it is the indicator of power, moreso than ET.

I've noticed that sometimes in a 1/4 mile drag situation, that with lower rear gears, that while ET can increase, trap mph can decrease, all else equal.
If I am reading correctly, you have been experiencing highr MPH trap speed with your lower gearing? Interesting.


If all else is equal,both LT5's make the same power or very close to it.
So,their trap speeds should be very close to the same. Only way that would be lower is if the engine is running out of breath at the lights.
As Bob said,only the ET matters in drag racing. MPH is just a by-product though it is a honest indicator of how much horsepower you're putting down.

[rhipsher]

Sure,you were starting to reel him in. His LT5 was probably starting to run out of breath in 4th gear with those 4.10's. Whereas,at 120mph,your car with the 3.73's was still hitting its stride.
But,you didn't catch him,did you?

I won't argue the point that 3.45's aren't an excellent cog for top-end blasts over 120mph. But,I ask the question once again: How many times a year does your ZR-1 see speeds way over 120mph? Probably,not that often. How often do you find yourself driving down the expressway in 5th gear,instead of 6th? When my car still had the 3.45's,I caught myself doing it quite often. To be perfectly honest,I wouldn't mind if our 94 had 3.45 cogs because the Texas speed limits are 75mph or even higher.
But,I still prefer a little more acceleration over a little more top end. Different strokes for different folks,, Clint as rare is it might be I am one of those guys that have gone well past the 120 mark on many occasions. And I can say from my experience that top speed is achieved in 5th with the stock 3.45. When I shifted into 6th gear I fell from 182mph to 168mph in a hurry. At top speed I was pegged at 7200rpm's. 4:10's might make 6th gear useful but I wonder if I would run out of RPM's before reaching top speed with them.
I'm with Pete on this one. If I had $1,500 to burn on performance mods I go with the ones that are actually going to create more HP. Because more HP is just more. And with 3.45 your going to see gains in every way. Launch and top end. Id rather have the overall increase than one or the other. ;)

[mgg]

I have read most of these post and it is a fascinating discussion. The one thing that no one has brought up is how does the single mass fly wheel affect al of this. I have a 90 ZR-1 with Marc's 510 hp package. I also installed 4:10s a few years ago. With the single mass flywheel getting to the torque curve and Hp sweet spot much more quickly I am curious how this would impact the discussion. Personally I really like the 4:10s. I only drag race once or twice a year. I don't own drag radials so trying to hook the car is just about pointless from a dead stop but it does pretty well from even a first gear roll. I am curious what the opinion is on how a single mass fly wheel would impact this discussion. I can tell that I am thrilled with the result of Marcs 510 package the gears etc. The car now has some "edge " to it and makes it really fun to drive. I know it will take some drag radials to take advantage of the launch but I 1/4 racing was not the biggest priority in purchasing one of these cars.

[rhipsher]

I have read most of these post and it is a fascinating discussion. The one thing that no one has brought up is how does the single mass fly wheel affect al of this. I have a 90 ZR-1 with Marc's 510 hp package. I also installed 4:10s a few years ago. With the single mass flywheel getting to the torque curve and Hp sweet spot much more quickly I am curious how this would impact the discussion. Personally I really like the 4:10s. I only drag race once or twice a year. I don't own drag radials so trying to hook the car is just about pointless from a dead stop but it does pretty well from even a first gear roll. I am curious what the opinion is on how a single mass fly wheel would impact this discussion. I can tell that I am thrilled with the result of Marcs 510 package the gears etc. The car now has some "edge " to it and makes it really fun to drive. I know it will take some drag radials to take advantage of the launch but I 1/4 racing was not the biggest priority in purchasing one of these cars.I did. Look at post number 5.:-D

[USAZR1]

Clint as rare is it might be I am one of those guys that have gone well past the 120 mark on many occasions. And I can say from my experience that top speed is achieved in 5th with the stock 3.45. When I shifted into 6th gear I fell from 182mph to 168mph in a hurry. At top speed I was pegged at 7200rpm's. 4:10's might make 6th gear useful but I wonder if I would run out of RPM's before reaching top speed with them.
I'm with Pete on this one. If I had $1,500 to burn on performance mods I go with the ones that are actually going to create more HP. Because more HP is just more. And with 3.45 your going to see gains in every way. Launch and top end. Id rather have the overall increase than one or the other. ;)

It's ok to disagree,Rick. Like I said earlier,different strokes for different folks.
I've been over 175mph too many times to count in my 90 ZR-1 while it still had 3.45's,,way over. Been over 200mph more than a few times too,on some of my turbo/nitrous prostreet bikes.
This is my 3rd ZR-1 so I've been around the block a few times,so to speak. :-D

Our 94 came with 4.10's when I bought it,a free mod.

BTW,good to see you posting again. Welcome back.

[Bearly Flying]

The Point being, if you want driveability, and NOT pure quarter mile performance, is the swap to 4;10's worth it?

I can already light up the tires at will with the 345's , if I drop to 4:10's it will only get worse?

I don't run 1/4 mile at all, just street driving.

[KILLSHOTS]

The Point being, if you want driveability, and NOT pure quarter mile performance, is the swap to 4;10's worth it?

I can already light up the tires at will with the 345's , if I drop to 4:10's it will only get worse?

I don't run 1/4 mile at all, just street driving.
If you want driveability, then yes, it is a great swap. I don't think I would do it again, given the same scenario of spending $1500 to have a mechanic complete the job. But if I was doing the work myself and only spending the $500 or so in parts, then yes, I would go for it. It changed the character of the car but surprisingly, it wasn't a lot more tail-happy. For what it sounds like you're looking to accomplish, it's a great swap.

[XfireZ51]

I went from 3.45s to 3.73s due to the 19" Z06 wheels I have. It effectively bumped my rear from a 3.30 to ~ 3.55. The car felt more responsive to throttle changes. It became more fun to drive.

[Bob Eyres]

4:10's might make 6th gear useful but I wonder if I would run out of RPM's before reaching top speed with them.
I'm with Pete on this one. If I had $1,500 to burn on performance mods I go with the ones that are actually going to create more HP. Because more HP is just more. And with 3.45 your going to see gains in every way. Launch and top end. Id rather have the overall increase than one or the other. ;)

According to Paul's gear charts the 4.10's give you 174.29@7,000 and 186.74@7,500. So you'd have to raise your rev limiter a bit, but you could get up there with 4.10's.

And as far as getting a better launch with more power, but stock gears, and the same tires....good luck.

Just what can you do on a ZR-1 for $1,500.00 that can give you the performance increase of 4.10 gears? Headers is the only thing I can think of, and that's only if you say good-bye to emissions compliance.

I bow down to Pete for his efforts to find the outer limits of the stock block ZR-1. Somebody's got to do it, and he's done a phenomenal job. The goal is to get into the tens with a stock block 350, and he's knocking on the door. But one look at his great 60ft. times with the 4.10's tells me that the right gear is the answer. My guess is that 4.30's or 4.56's and the right tire would get him there, because then he's using all the revs available. Running a three speed ZR-1 is like trying to do it with your hands tied.

[Bob Eyres]

The one thing that no one has brought up is how does the single mass fly wheel affect al of this. I have a 90 ZR-1 with Marc's 510 hp package. I also installed 4:10s a few years ago. With the single mass flywheel getting to the torque curve and Hp sweet spot much more quickly I am curious how this would impact the discussion. Personally I really like the 4:10s. I only drag race once or twice a year. I don't own drag radials so trying to hook the car is just about pointless from a dead stop but it does pretty well from even a first gear roll. I am curious what the opinion is on how a single mass fly wheel would impact this discussion. I can tell that I am thrilled with the result of Marcs 510 package the gears etc. The car now has some "edge " to it and makes it really fun to drive. I know it will take some drag radials to take advantage of the launch but I 1/4 racing was not the biggest priority in purchasing one of these cars.

I've found that the lightweight flywheel improves the performance of the LT5 everywhere but at the launch.
Once you're hooked up and moving though, the light weight unit gives you an advantage throughout the run, by using less horsepower that it takes to spin it.
Bottom line, shorter gears=advantage, lightweight flywheel=advantage, Marc's 510 package=big advantage.

You have the one performance "problem" that we all love to have, traction :dancing
If you don't want Drag Radials, check out the thread on the Toyo Proxes 888's. they look like a good alternative, if you don't put a lot of mileage on the car.

[5ABI VT]

I believe many of you are just not understanding what gears do. Please re-read my post about final drive ratios of 3.45 vs 4.10. the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference. IF the 4.10s were making you faster throughout the entire rpm range and through the gears there would be a mph difference but there is none. if you are gaining mph its possibly due to being at a better rpm through the traps where after the traps they would even out again.

Using 6th is not smart. its a .5 ratio. DESIGNED FOR FUEL ECONOMY ONLY. it shares a synchro with reverse so get ready to melt your synchro and destroy your zf if you are using it for acceleration.

I ran almost 118mph with stock gears. headers and a tune and emissions compliant. On 25 series tires pumped to 48 psi if I remember right on 450 lb springs. Set up for 1/4 mile it is not but right at home at high speed.


It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc. if the motor truly needed 4.10 gears, the motor should peak power well higher than what an LT4 does. it would have pushed the hp and torque curver higher and 4.10 gears would have been justifiable because it would bring the torque back in the low end. As it is now on a stock motor I feel 4.10 gears just makes it too torque for a street tire and the increased rpm range isn't really used because of the way the cams are profiled etc.

If I ever have the chance and $$ to build a serious LT5 I would build a big bore LT5 to spin the maximum rpm possible (8000-8500?) then and only then would I drop a 4.10 in the back because the cams would be profiled to be efficient at a much higher rpm causing a noticeable reduction in low rpm torque.

Im babbling just bored at work. Gears are very misunderstood. In my opinion it was a trick first started by the drag cars to get off the line faster because that's all it really does.. have a shorter 1st gear.
:cheers:

[XfireZ51]

"It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc."

I'm not sure about a totally stock LT-5, but my ported top end w headers and stock cams(not degreed) peaked at ~6800rpm. Still does now.
I think there's more cam there than air available.

[5ABI VT]

"It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc."

I'm not sure about a totally stock LT-5, but my ported top end w headers and stock cams(not degreed) peaked at ~6800rpm. Still does now.
I think there's more cam there than air available.

That is making use of what I feel is the LT5s greatest attribute. RPM =D>

[Bob Eyres]

" the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference."

With all due respect, I think you are defeating your argument in the first paragraph.

Let's establish that we're talking about performance in the quarter mile here, not overall performance in every situation.

You agree that 4.10's have an e.t. advantage in the quarter mile. In a drag race low e.t. wins, end of story.

Once again you mention "mph difference". The only thing that mph in the traps means is that it is an indirect indication of horsepower, of potential.
A car with a mediocre e.t. and a high mph reading in the time traps is a loser. Lots of power, but not set up for the drag strip.

As I see it, the goal in quarter mile gearing setup is to achieve the lowest short time possible (60ft.), then reach the end of the track at the top of the top gear, (4th in most cases).

In our ongoing example, Pete cut his lowest yet 60ft. time with 4.10 gears, but complained that by using fourth gear he reached the end of the track without reaching his desired peak rpm of 7,400. In my opinion, the way to fix that is an even higher gear, 4.30's or 4.56's depending on what tires are available to handle it. The lower the gear, the lower the potential 60ft. time. As long as you can use all of your available rpm at the other end of the track.

BTW, you mentioned that you trapped 118mph. with just headers and a tune. Is that a 375 or 405hp. ZR-1? And what was the actual tire size? thanks.

[Dynomite]

Not discussed so far.......what rpm do you drop the clutch and how fast can you shift (power shift?). If you are spinning your tires in first gear, does it matter what rear end ratio you have?

How does car acceleration vary with how fast you are spinning your tires?

Does traction vary with tire spin?

After you have spun your tires with 4:10s for a bit in first gear you are shifting into a range that is different in every gear with 4:10s as compared to 3:45s (but shifting into the maximum engine power curve zone "rpm vrs hp" each time) requiring you to shift into 4th at the end of the 1/4 mile. So the difference is at the start of the 1/4 mile and near the end of the 1/4 mile only.

Maybe I have it wrong but depends a lot on tires (traction) at least in 1st gear and second gear in a power shift :p

[5ABI VT]

With all due respect, I think you are defeating your argument in the first paragraph.

Let's establish that we're talking about performance in the quarter mile here, not overall performance in every situation.

You agree that 4.10's have an e.t. advantage in the quarter mile. In a drag race low e.t. wins, end of story.

Once again you mention "mph difference". The only thing that mph in the traps means is that it is an indirect indication of horsepower, of potential.
A car with a mediocre e.t. and a high mph reading in the time traps is a loser. Lots of power, but not set up for the drag strip.

As I see it, the goal in quarter mile gearing setup is to achieve the lowest short time possible (60ft.), then reach the end of the track at the top of the top gear, (4th in most cases).

In our ongoing example, Pete cut his lowest yet 60ft. time with 4.10 gears, but complained that by using fourth gear he reached the end of the track without reaching his desired peak rpm of 7,400. In my opinion, the way to fix that is an even higher gear, 4.30's or 4.56's depending on what tires are available to handle it. The lower the gear, the lower the potential 60ft. time. As long as you can use all of your available rpm at the other end of the track.

BTW, you mentioned that you trapped 118mph. with just headers and a tune. Is that a 375 or 405hp. ZR-1? And what was the actual tire size? thanks.

You are correct and i guess Ill clarify that IF you can take advantage of a short first gear with a suspension/tire setup for launch gears can make you 'quicker'. in Petes case i also agree that more gear can shave some more et assuming hes got the setup to launch hard and be at the right rpm to see some mph increase before the traps.

Im not a drag racer and make no secret to voice my opinion on why I don't like it but I think drag racing is about whos quicker not faster. Its just my preference and mph to me is everything. A car can run 10s and go 120 and I can be doing 13s and doing 130mph. ill be happy because if he rolled up beside me on the freeway where I do most my spirited driving I would walk away and ultimately be 'faster'.

I guess all im trying to say is for those who are considering gears.. if you are drag racing and have the suspension setup to hook first gear with an aggressive launch or are looking to optimize the gearing for the 1/4 mile. .. gears are easily justifiable.

I find most people tend to compare gear to gear ie. 3rd gear with stock rear vs 3rd gear with 4.10s. I think that most people fail to consider that the speed range in each gear has been reduced and it would be more fair to compare a 2nd gear with stock rear vs 4.10s in 3rd. That usually makes people think.

My z is a 94. Headers catted to corsa with haibeck chip. tires 315/25/19 on Invos which pretty much grip like all seasons lol.

[Paul Workman]

That is making use of what I feel is the LT5s greatest attribute. RPM =D>

Yup!

That and a relatively flat torque curve!

I've watched the result of the high rpm performance, and others* have noticed too that lots of cars may jump a ZR-1 at the light, but time after time the LT5s will run 'em down on the big end. As Bob G says, "Just about the time (pushrod motors) are getting interesting, you have to shift!" So many times, if the Z lost the 1/4 mile contest, it was gaining and just ran out of track.

Watch what happens at every shift the C5 makes... (I especially like the jubilant "Ha!" when the C5 lunges ahead...followed by the perplexed, "Huh???" as the Z is walking away. And then the reality sinks in: "Your not catchin' him!!")

http://www.youtube.com/watch?v=PzPPEK9Qf3M


And, the numbers seem to agree. Race results from the 1/2 mile shootout in Chicago last spring showed the LT5s - and their decades older technolgy - really took no guff from contemporary pushrod motors. The did really well!

[mike100]

I think most people understand the phenomenon of low gears vs high once you have driven a car with both, but have a hard time explaining it all in words. there are a lot of complex things going on and it isn't just a straight algebraic torque multiplication definition. Mathematically, you want to dwell in the fattest part of the hp curve and spend the least amount of time lugging off the line.

- You can integrate the function (hp curve) and gear the transmission accordingly to drop you back where the engine runs right (more gears or custom ratios in the ZF which don't exist).

-you can gear down the diff to reduce break-away tire spin (tall gears sometimes result in massive runaway burnout speed) and tires deal with wheel slip better if the slip speed isn't too much.

-you can figure out a way to shift faster (automatics and twin-clutch PDK types come to mind)

-or you can put a 400 cubic inch engine in to be able to accelerate harder regardless of gearing.

Obviously the transmission is probably the best place to see gains, but since that isn't available with the ZF, adding power makes sense (not to mention fun).

[JFFerner]

I think everyone has about covered everything with the exceptions of up-hill vs. downhill and headwind vs. tailwind!
And so it goes....Jim

[ZZZZZR1]

Great discussion and explanations with different points of view!!!

I think this is one of the best upgrades for the ZR-1...

I know a few with 4:30 and 4:56 gears! Now that's tall!

:cheers:

David

[rhipsher]

:dancingTrue it is that a Fidanza flywheel is much harder to launch from a stand still than the stock DM due to loss of inertia. I launched at about 2500rpm's with the DM. But with the 13.5 lbs fidanza I found the best launches came at 4500rpm's. And even with Mickey Thompson drag radials on it was a fine line between lighting them up and bogging down at the Christmas tree. But with a line lock you can heat the drag radials up enough to grab and explode drive train parts lol! MT's heated up properly make for awesome launches though. You will jump out of the whole 20 feet. I mean look at the torque squat on that red SOB! It was Mickey Thompson awesome.
http://i301.photobucket.com/albums/nn63/keeno1970/DSC01537.jpg
http://i301.photobucket.com/albums/nn63/keeno1970/DSC01538-2.jpg
Hanging out after 11 runs down the dragstrip with my buddy Mike Johnson and his convertible C5. This was back when I was eating to many donuts. You know that the 90 ZR-1's are the worst seats for fat people to fit in lol.:-D At 187 I fit fine now.
http://i301.photobucket.com/albums/nn63/keeno1970/DSC01529.jpg

[Schrade]

Very well put.

Should be 'end of story'. Again...

I believe many of you are just not understanding what gears do. Please re-read my post about final drive ratios of 3.45 vs 4.10. the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference. IF the 4.10s were making you faster throughout the entire rpm range and through the gears there would be a mph difference but there is none. if you are gaining mph its possibly due to being at a better rpm through the traps where after the traps they would even out again.

Using 6th is not smart. its a .5 ratio. DESIGNED FOR FUEL ECONOMY ONLY. it shares a synchro with reverse so get ready to melt your synchro and destroy your zf if you are using it for acceleration.

I ran almost 118mph with stock gears. headers and a tune and emissions compliant. On 25 series tires pumped to 48 psi if I remember right on 450 lb springs. Set up for 1/4 mile it is not but right at home at high speed.


It is true the LT5 has more rpm but many of you are not realizing what the truth is. GM didn't want to alter rear gears or the zf SO Lotus was asked to build a dohc 32v motor that still had peak power at what.. 5800 ? I could bet something that Lotus was like WTF when gm asked them to do that. Basically they cammed and setup the potential screamer to act just like a wheezing pushrod sbc. if the motor truly needed 4.10 gears, the motor should peak power well higher than what an LT4 does. it would have pushed the hp and torque curver higher and 4.10 gears would have been justifiable because it would bring the torque back in the low end. As it is now on a stock motor I feel 4.10 gears just makes it too torque for a street tire and the increased rpm range isn't really used because of the way the cams are profiled etc.

If I ever have the chance and $$ to build a serious LT5 I would build a big bore LT5 to spin the maximum rpm possible (8000-8500?) then and only then would I drop a 4.10 in the back because the cams would be profiled to be efficient at a much higher rpm causing a noticeable reduction in low rpm torque.

Im babbling just bored at work. Gears are very misunderstood. In my opinion it was a trick first started by the drag cars to get off the line faster because that's all it really does.. have a shorter 1st gear.

[ZRXMAX]

I believe their is a thesis full of info here and I stopped reading at page 8! :wink:

My car has spent much of its life with 307s in it from the ORR I ran in 05. What is their to like about 307s besides running 180 mph in 5th at 5300 rpm ?
Less shifting is and a little bit better gas milage under the right conditions.
200 ft burnouts when your wanting to get rid of some rear tires aren't a problem either.

I remember years ago a couple guys in Texas with ZR-1s that were evenly matched commented on the difference between 3.45s and 4.10 gears. They said their was no noticeable difference in acceleration and were amazed by that fact. They both leaned towards thinking the 4.10s would help the LT5 accelerate quicker as I recall.

I do like the fact that 4.10 gears make the drop in rpm a little less between gears when shifting at 7000 rpm.

I tried a set of 4.30s for a while and didn't really like them especially when out a couple hundred mile cruise.

I have a new set of 4.10s ready to go and I am looking forward to it. :cheers:

[Schrade]

I believe their is a thesis full of info here and I stopped reading at page 8! :wink:

My car has spent much of its life with 307s in it from the ORR I ran in 05. What is their to like about 307s besides running 180 mph in 5th at 5300 rpm ?
Less shifting is and a little bit better gas milage under the right conditions.
200 ft burnouts when your wanting to get rid of some rear tires aren't a problem either.

I remember years ago a couple guys in Texas with ZR-1s that were evenly matched commented on the difference between 3.45s and 4.10 gears. They said their was no noticeable difference in acceleration and were amazed by that fact. They both leaned towards thinking the 4.10s would help the LT5 accelerate quicker as I recall.

I do like the fact that 4.10 gears make the drop in rpm a little less between gears when shifting at 7000 rpm.

I tried a set of 4.30s for a while and didn't really like them especially when out a couple hundred mile cruise.

I have a new set of 4.10s ready to go and I am looking forward to it. :cheers:

How many miles on your 3.07? You selling the set?

[ZRXMAX]

How many miles on your 3.07? You selling the set?

This is my second set and they came out of a 47,000 mile car. I ran the 1st set out of oil when I let it sit to long with a slow leak a few years ago.

The set I have now probably have less than 60K on them. I will keep them for the next opportunity I get to run another ORR. Sorry...

Another thing about 307s is they are a little bit harder on your clutch overall. If you have to take off on a steep incline you will slip the clutch a bit more to get underway... or you can rev it a little and just pop the clutch.

You shouldn't have to look to long for a set. Both of mine came from early C4s that had 4 + 3 setups. My 89 6 speed coupe had 3.33s in it and you might be able to find a set of those if you can't find any 3.07s. I just look for the whole assembly including the batwing.

I do have an empty 44 housing here if your interested in starting with that.

[Bob Eyres]

I've been in love with the short gears since back in 1970, (when I was a kid:)). My first Corvette was a beat up $800.00 Split window with 340hp., a high winding solid lifter small block with 4.56 gears. Kind of like the ZR-1 of it's day.
I put some, new for the time, wide F60x15" Goodyears on 8" wide station wagon rally wheels on all 4 wheels.
That thing would squat down and launch like a demon. Two of my friends had big blocks, one a brand new 69' 427/435hp coupe, and the other guy had a 66' GTO with an L88 crate motor. But at launch, and in first gear, neither of them could beat the 63'. By the end of second gear though, I was toast. :cheers:

[Dynomite]

Good information and great photos....thanks :handshak:

Cliff

True it is that a Fidanza flywheel is much harder to launch from a stand still than the stock DM due to loss of inertia. I launched at about 2500rpm's with the DM. But with the 13.5 lbs fidanza I found the best launches came at 4500rpm's. And even with Mickey Thompson drag radials on it was a fine line between lighting them up and bogging down at the Christmas tree. But with a line lock you can heat the drag radials up enough to grab and explode drive train parts lol! MT's heated up properly make for awesome launches though. You will jump out of the whole 20 feet. I mean look at the torque squat on that red SOB! It was Mickey Thompson awesome.
http://i301.photobucket.com/albums/nn63/keeno1970/DSC01537.jpg
http://i301.photobucket.com/albums/nn63/keeno1970/DSC01538-2.jpg
Hanging out after 11 runs down the dragstrip with my buddy Mike Johnson and his convertible C5. This was back when I was eating to many donuts. You know that the 90 ZR-1's are the worst seats for fat people to fit in lol.:-D At 187 I fit fine now.


I believe many of you are just not understanding what gears do. Please re-read my post about final drive ratios of 3.45 vs 4.10. the ONLY advantage 4.10s gives you is 1st gear. When you go to 2nd the leverage advantage goes to the stock gears while still in first. and it passes back and forth. That is why there is a ET advantage with 4.10s but no MPH difference. IF the 4.10s were making you faster throughout the entire rpm range and through the gears there would be a mph difference but there is none. if you are gaining mph its possibly due to being at a better rpm through the traps where after the traps they would even out again.


What I also suggested in post 87....thanks...I think you said it better :thumbsup:
The issue then becomes the last shift into third or even fourth for those with 4:10s. :p

[A26B]

I've found that the lightweight flywheel improves the performance of the LT5 everywhere but at the launch.
Once you're hooked up and moving though, the light weight unit gives you an advantage throughout the run, by using less horsepower that it takes to spin it.
Bottom line, shorter gears=advantage, lightweight flywheel=advantage, Marc's 510 package=big advantage.

You have the one performance "problem" that we all love to have, traction :dancing
If you don't want Drag Radials, check out the thread on the Toyo Proxes 888's. they look like a good alternative, if you don't put a lot of mileage on the car.

Now, with more choices of flywheel weight, combined with gear options, should allow for dialing in what works best with individual tire, engine combos.

Fidanza 13#
Jerrys Gaskets 18# (alum billet)
Jerrys Gaskets 22# (alum billet)
Stock D/M 33#
McLeod (unk)

[Bob Eyres]

Right. Mine is an old Doug Rippie unit. A machined down stock Camaro single mass that weighs about 15lbs. It has worked well for 17 yrs.

BTW,What is the weight of the newest light weight flywheels?

[Hog]

I do like the fact that 4.10 gears make the drop in rpm a little less between gears when shifting at 7000 rpm.

:cheers:Lower gearing like 4.10's or 4.56's wont affect on the eamount of rpm drop when upshifting. Transmission gearing is the only way to affect the rpm drop when shifting. This is where the terms, Close-Ratio and Wide ratio transmissions come into play, with the close ratio usually having less rpm drop during upshifts.

[Hog]

If all else is equal,both LT5's make the same power or very close to it.
So,their trap speeds should be very close to the same. Only way that would be lower is if the engine is running out of breath at the lights.
As Bob said,only the ET matters in drag racing. MPH is just a by-product though it is a honest indicator of how much horsepower you're putting down.

Yes, all else equal means that the cars are assumed to have identical variables, including having the exact same engine power output. The only variable being rear dif. gearing.

"Only way that would be lower is if the engine is running out of breath at the lights."
This makes 100% sense. I believe this to be the case in my setup, in going from a 3.08 to a 4.10 gear has had me trapping at an rpm that is beyond my power peak, where power is dropping off fast. Thanks for explaining.

xxxxxxxxxxxxxxxxxxxxxxxxx
Yes, ET is what matters in drag racing. If I cut a 2.0 60ft on pass #1 and trap a 12.0@100mph. Then on run #2 I lose traction off the line and run a 2.5 60ft time, I could theoretically run a considerably worse ET such as 13.0 seconds, yet still run the same MPH.

It could be argued that in drag racing, ET is as irrelevant as MPH because of the fact that having the quicker ET doesnt necessarily mean you will win the drag race.
ET is of course the most common method of comparing a cars acceleration. If all variables are the same, MPH is an accurate fashion in which to compare engine power.

Thank you !

[ZRXMAX]

Lower gearing like 4.10's or 4.56's will have zero effect on the eamount of rpm drop when upshifting. Transmission gearing is the only way to affect the rpm drop when shifting. This is where the terms, Close-Ratio and Wide ratio transmissions come into play, with the close ratio usually having less rpm drop during upshifts.

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s :)

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

[Hog]

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s :)

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

I use that same rpm calculator as well, small world.

In this example, you are comparing how much MPH youwwill get out of each trans gear using a 4.10 or 3.07 gear. Not the amount of engine rpm drop that will occur when you shift from 1st gear to 2nd gear.

Using the exact same parameters you have used.
3.07 rear gear ratio
shiftpoint=7000rpm
tire height 25.5"
rear gearing 3.07
trans 1st rear ratio=2.64:1
=65.5mph @ 7000rpm in 1st gear

Now you shift to 2nd gear from a hypothetical shift rpm of 7000rpm, same variables except the 2nd gear trans ratio of 1.78:1.
Now you will be travelling at 65.5mph in 2nd gear, with your tach now registering 4725 rpm.
Shiftpoint rpm minus resultant rpm in 2nd gear, for 3.07 gears
=7000rpm - 4725rpm
=2275rpm
= For 3.07 rear gears the RPM drop of 2275rpm when shifting from 1st gear to 2nd gear

4.10 rear gear ratio
Now lets repeat for a 4.10 gearing scenario
Shiftpoint =7000rpm
tire height 25.5"
rear gearing=4.10
trans 1st rear ratio=2.64:1
=49.0mph @ 7000rpm in 1st gear

Now we shift to 2nd gear at our hypothetical 7000rpm shiftpoint, same variables except 2nd gear ratio of 1.78:1. Now we will be travelling at 49mph in 2nd gear, with the tach reading 4725rpm.

Shiftpoint rpm minus resultant rpm in 2nd gear, for 4.10 gears
7000rpm - 4725rpm
=2275RPM
=For 4.10 rear gears, the RPM drop of 2275rpm when shifting from 1st gear to 2nd gear.

As you can see, the rpm drop in both cases is exactly the same, therefore rear gear ratios have no effect on amount of engine RPM drop when upshifting. The only way to change the amount of rpm drop during an upshift is to change the gearing inside the transmission.

[XfireZ51]

From what I am reading here, it would explain why I would be accelerating on Lgaff's car in the second 1/8. Just run out of real estate to catch up.

[USAZR1]

Little did I know how much money I wasted changing gearing in so many cars & bikes over the last 45 years..
Carry on,mates! :-D

[ZRXMAX]

Little did I know how much money I wasted changing gearing in so many cars & bikes over the last 45 years..
Carry on,mates! :-D

I don't know about the wasted part you mentioned Clint. Back in the day I changed sprockets on my 750 Honda from 18-48 to 16-52. From that point on I could do wheelies from a dead stop! :-D

[Bob Eyres]

It could be argued that in drag racing, ET is as irrelevant as MPH because of the fact that having the quicker ET doesnt necessarily mean you will win the drag race.


Except for one thing, E.T. is the only relevant factor.
Except for the factor of who leaves first, who gets the jump.
That's the essence of bracket racing, which programs the tree to hold back the the quicker car to make the race even. Then, whoever responds to the light quicker theoretically wins.
In a "heads up" race, both drivers respond to the same light sequence. If both cars run the same e.t., then whoever leaves first wins.

This puts driver skill into the equation. Shifting quicker also allows you to minimize the rpm drop between gears.

[Schrade]

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s :)

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

I had one installed in my automatic conversion. SGI-5 C

Worked properly at speed, but at '0' MPH, it gave an erratic reading, for which there was a troubleshoot symptom. Followed it to a 'T', and didn't solve the problem.

Ended up removing it, and using the Tranny Control Module for speed signal feed.

Solved it. Sold the DD on eBay, guy had no problems with it on his project wheels...

http://www.zr1.net/forum/showthread.php?t=19299

[XfireZ51]

Using 19s and 3.55s, the stock trans speedo gear puts me at about 3mph low on the speedo when running 70mph. Something along the lines of 3-4% off which is acceptable to me.

[Pete]

They must've installed it wrong.
Have DD in the 441 auto Z for about 10 years works great no issues.

Pete

[Hog]

Except for one thing, E.T. is the only relevant factor.
Except for the factor of who leaves first, who gets the jump.
That's the essence of bracket racing, which programs the tree to hold back the the quicker car to make the race even. Then, whoever responds to the light quicker theoretically wins.
In a "heads up" race, both drivers respond to the same light sequence. If both cars run the same e.t., then whoever leaves first wins.

This puts driver skill into the equation. Shifting quicker also allows you to minimize the rpm drop between gears.

That was my point, there are ways for a slightly slower car to win a drag race against a quicker car.

Yes in bracket racing, if both cars run their dial in, the car that crosses the finish line first gets the win, so long as you dont "breakout" and run a lower ET than your "dial-in".
I remember being in a money class for eliminations. There were cars that sat on the line for many seconds before they got to launch. I see them launch wheels up in my rearview mirror and then charge by me at the finsh line. The guy was choked that he lost though.


Using the Pro tree in "heads up" drag racing whichever car gets to the finish line without "red-lighting" wins. The ET you run in this type of drag racing doesnt matter. ET is meaningless in heads up because the timers for your own lane dont start until your vehicle moves, and end when your car breaks the beams at the finish line.

On the quicker shifting. Having quick shifts on a manual trans increases the amount of time that the drive wheels are putting power to the ground. The only way rpm drop during an upshift would increase appreciably is if shifted VERY slowly. Slow enough that the car actually loses speed during the shift, otherwise rpm in a manual trans car is pretty constant. This is where an automatic has an advantage, power is always being transmitted to the rear drive wheels during upshifts. But thats a different discussion.

[Hog]

Using 19s and 3.55s, the stock trans speedo gear puts me at about 3mph low on the speedo when running 70mph. Something along the lines of 3-4% off which is acceptable to me.

I see you mentioning 19" rims often, but what is your tire height? Curious.
Thanks.

[Paul Workman]

I see you mentioning 19" rims often, but what is your tire height? Curious.
Thanks.

OR, better yet, is what is the center wheel to pavement height - allowing for some "squish" factor?

[USAZR1]

I see you mentioning 19" rims often, but what is your tire height? Curious.
Thanks.


Fronts are 275/35/19 (26.6")
Rears are 335/30/19 (26.8")

[Bob Eyres]

ET is meaningless in heads up because the timers for your own lane dont start until your vehicle moves, and end when your car breaks the beams at the finish line.

On the quicker shifting. Having quick shifts on a manual trans increases the amount of time that the drive wheels are putting power to the ground. The only way rpm drop during an upshift would increase appreciably is if shifted VERY slowly. Slow enough that the car actually loses speed during the shift, otherwise rpm in a manual trans car is pretty constant. This is where an automatic has an advantage, power is always being transmitted to the rear drive wheels during upshifts. But thats a different discussion.

I know what you're saying, but I don't think e.t. is meaningless in a heads-up race. I think what you mean is that e.t. isn't the only factor, and that the quicker car can still lose if his reaction time is slower, giving the slower car an advantage.

On the quicker shifting issue, I think about it in terms of inertia. The difference between a power shift, and a granny shift, is that in a power shift the gas pedal is on the floor throughout the shift. When the clutch is disengaged, the rpms shoot up, the shift is made while this is happening, and when the clutch re-engages, the power is higher than before, therefore helping the engine rpm stay up higher in it's power band.
In the granny shifted car, shifted at the same rpm, as the clutch disengages the driver lets off the gas until the clutch is re-engaged. As it re-engages the rpms are lower than before, and pulled down further by the next gear. This loses inertia. The engine has to climb that rpm mountain again, three times during the race, (twice in a three speed car). It goes with out saying that when you are letting off the gas three times during the race, even for milliseconds, that is slowing you down.

Wear and tear on the gearbox is obviously the downside to power shifting. I've been through 3 transmissions doing this. So, now that I'm a Grandpa, I shift like Granny tells me to. :redface:

[Hog]

I know what you're saying, but I don't think e.t. is meaningless in a heads-up race. I think what you mean is that e.t. isn't the only factor, and that the quicker car can still lose if his reaction time is slower, giving the slower car an advantage.

On the quicker shifting issue, I think about it in terms of inertia. The difference between a power shift, and a granny shift, is that in a power shift the gas pedal is on the floor throughout the shift. When the clutch is disengaged, the rpms shoot up, the shift is made while this is happening, and when the clutch re-engages, the power is higher than before, therefore helping the engine rpm stay up higher in it's power band.
In the granny shifted car, shifted at the same rpm, as the clutch disengages the driver lets off the gas until the clutch is re-engaged. As it re-engages the rpms are lower than before, and pulled down further by the next gear. This loses inertia. The engine has to climb that rpm mountain again, three times during the race, (twice in a three speed car). It goes with out saying that when you are letting off the gas three times during the race, even for milliseconds, that is slowing you down.

Wear and tear on the gearbox is obviously the downside to power shifting. I've been through 3 transmissions doing this. So, now that I'm a Grandpa, I shift like Granny tells me to. :redface:


Semantics, quickest car, with the best reaction time wins.

I agree 100% with you during a proper "powershift". Including the factors that you describe, which are 100% correct, there is also the slight torque multiplication that occurs as the friction materials slip as they come together as the clutch is released. This multiplicarton is only apparent while the clutch disc and the flywheel are turing at different rates. Once the rates are equalized, only gearing supplies the multiplication.

I apologize for the "granny" shifting term. No matter anyones age, they deserve the same respect (perhaps more) that someone of another age.



USA ZR-1 thanks for the specs.

[Bob Eyres]

Semantics are important if you want your meaning to be clear.

I've never understood the semantics of the term "torque multiplication". I've seen it used, mostly, to describe the advantage the automatic transmission has, at launch, in the quarter mile. The torque converter allows enough slippage to let the engine come higher into it's power band before the car starts moving. So that you have more power available at launch. The automatic has other advantages, and disadvantages, but I don't see how torque is literally "multiplied" in any way. Semantics :confused:

[XfireZ51]

I see you mentioning 19" rims often, but what is your tire height? Curious.
Thanks.

I have 19s on the back. The fronts are 18s. Just measured the rears sitting there w ~ 35psi, they stand at 26.25". Size is 325/30/19. These are the Nitto Invos which I like quite a bit. Good wet, fairly quiet, and grab pretty well on hard shifts.

[Hog]

Semantics are important if you want your meaning to be clear.

I've never understood the semantics of the term "torque multiplication". I've seen it used, mostly, to describe the advantage the automatic transmission has, at launch, in the quarter mile. The torque converter allows enough slippage to let the engine come higher into it's power band before the car starts moving. So that you have more power available at launch. The automatic has other advantages, and disadvantages, but I don't see how torque is literally "multiplied" in any way. Semantics :confused:

Semantics in the actual number expressed as an ET being meaningless to me, while being a factor to you. In other words, I was willing to drop the subject of ET importance, based on semantics. Semantics being "the
meaning, or an interpretation of the meaning, of a word (http://dictionary.reference.com/browse/word), sign, sentence, etc.: Let's not argue about semantics."
xxxxxxxxxxxxxxxxxx

The torque multiplication of a torque converter is in play whenever there is a greater force applied to the torque torque converter, as like you described during a standing start, but also down range and during upshifts.

Torque converters have an STR or K value. STR means Stall Torque Ratio. Usual STR's for stock GM TC's are 1.8. SO if you input 100 lb/ft you get 180 lb/ft applied to the input shaft.
The only time the STR is taken out of the equation when applying an acceleration force is when the Torque Converter Clutch is applied, then the engine torque is applied to the input shaft of the trans in a 1:1 ratio.

As I stated torque multiplication occurs in a standard clutch as well, while it is slipping. Not advisable in a conventional clutch, but it's advantages can be seen in a slipper clutch design. Whenever 2 friction materials are forced together yet move at differnt speeds, torque is multiplied. The difference in a TC is that instead of 2 friction materials, when have "fans" of different pitches driving and being driven by an incompressible fluid, in effect, performing the same torque multiplication that that a ZF-6 performs, except by using a fluid instead of mechanical gear contact and the amount of torque multiplication is controlled by blade design in the TC and gear tooth counts in the ZF-6.

Torque Multiplication occurs through a manual clutched trans as well, input 100 lb/ft into the input shaft of a ZF6 in 1st gear, and 266 lb/ft will be seen on the trans output shaft(assuming zero loss).

At least that the way I understand it, using my personal base of semantics.

xxxxxxx

Thanks X-Fire for the tire specs.

[WVZR-1]

For any calculations that require tire specifications you don't rely on "advertised" specifications or those of Tom, Joe, Jim or Bob. A very simple procedure that produces "correct" number to be used for calculations can be accomplished with a simple "square", chalk and a measuring tape.

Chalk the tire and the floor/asphalt at 6 o'clock using the square through the axle/hub center, then move the car "one tire rotation" and duplicate the chalk mark on the floor/asphalt, measure that dimension and you've a "rolling circumference" from which you can do any calculations you wish to accomplish accurately. Ideally the car should be at customary fuel load with the driver on board or his weight duplicated in the seat and at temperature. That's a "stretch" of course but it's real.

You've got what you know are good dimensions and no "Internet" lore or guesses from the multitudes.

All the references to 17", 18' and 19" are irrelative to most anything including brake packages. Caliper clearances are determined by the barrel specifications of a wheel not the tire mounting diameter.

The dimension mentioned for the 325/30R19 is center of rear axle to asphalt X 2 or asphalt to top of tire? It makes a difference. The rotation for circumference removes all doubt for "your car".

[Blue Flame Restorations]

If you can't feel a difference, something's not right. I loved my 4:10's.

[WVZR-1]

A friend asked me to evaluate a "calculator" and I don't generally use these calculators if it can be done with simple math but this one could be very interesting in rear gear, tire selection and just a better and simpler working knowledge of what is affected by which. If you have an accurate tach and speedometer, you can measure your tire circumference as I mentioned in a post a couple up (#122) and be better prepared to maybe buy a gear or select a tire size.

It won't make an argument for a light or heavy flywheel but you can easily see the RPM drops with the gear selections (the shift from 1 to 2, 2 to 3, 3 to 4 etc). I didn't check it first hand but with there being so many different "max power RPM" documentations this can be tweaked to each individual car. You can compare the axle ratios, various tire dimensions and maybe make a better choice in the selection of the rear gear or tire.

You just need to validate the MPH/RPM in the lower most portion and like I mentioned have an accurate tach and speedometer. I believe the link will open with the correct ZF ratios but I'll look again and you could confirm your self. I believe the ratio choices that I placed are correct for the Zf. I've read a couple different but these are what I believe I see most frequently.

I used the default tire Dominic mentioned and that's a 677.6 (by spec), he mentions 26.25 (666.750) so if he just substitutes that diameter then and modifies the RPM to what he feels his is then he should see pretty accurate #'s BUT he mentions also that his speedometer isn't accurate so the results would be skewed. If your speedometer is accurate and tach is also, these #'s should be quite reliable.

http://www.cargister.com/calculator-gear-ratio?rpm=6800&final_ratio_teeths

The ratio for the ZF didn't transfer so here they are and you can do the input manually. 1st = 2.68, 2nd = 1.80, 3rd = 1.29, 4th = 1.0, 5th = .75, 6th = .5

I pasted the URL a couple times and it was complete but the URL won't paste here complete. How reliable? The numbers on paper that I checked RPM/MPH looked to be accurate IF the diameter is supplied correctly and not relying on the advertised tire specs and results using only the tire size.

End result is a graph showing RPM loss at each shift made at MAX power:

3583

MPH @ RPM for each gear like this:


Gear shift

Difference after shifting

RPM after shifting

from 1st Gear to 2nd Gear 2233 4567
from 2nd Gear to 3rd Gear 1927 4873
from 3rd Gear to 4th Gear 1529 5271
from 4th Gear to 5th Gear 1700 5100
from 5th Gear to 6th Gear 2267 4533


mph / RPM
1000 2000 3000 4000 5000 6000 6800
1st Gear 7.9 15.9 23.8 31.8 39.7 47.6 54
2nd Gear 11.8 23.6 35.5 47.3 59.1 70.9 80.4
3rd Gear 16.5 33 49.5 66 82.5 99 112.2
4th Gear 21.3 42.6 63.8 85.1 106.4 127.7 144.7
5th Gear 28.4 56.7 85.1 113.5 141.8 170.2 192.9
6th Gear 42.6 85.1 127.7 170.2 212.8 255.3 289.4

[XfireZ51]

BTW using my GPS for accurate MPH. when I compare that to speedo, speedo is about 3-4mph slower at 70+. I am sure there is "some" growth in the circumference of the tire due to heat and centripetal(sp?) force. Never could get that and centrifical force straight. :(

Also everyone, there is a way to mitigate the rpm drop from an aluminum flywheel within the calibration. Its a very crude version of Rev-Match utilizing what's called the Throttle Follower.

[Paul Workman]

*...Also everyone, there is a way to mitigate the rpm drop from an aluminum flywheel within the calibration. Its a very crude version of Rev-Match utilizing what's called the Throttle Follower.

I'm not clear what you mean by rpm drop, as it relates to an aluminum FW. I'll take an SWAG and say it relates to rpm loss between gears (I'm assuming??).

[XfireZ51]

I'm not clear what you mean by rpm drop, as it relates to an aluminum FW. I'll take an SWAG and say it relates to rpm loss between gears (I'm assuming??).

Yes.

[USAZR1]

Lower gearing like 4.10's or 4.56's wont affect on the amount of rpm drop when upshifting. Transmission gearing is the only way to affect the rpm drop when shifting. This is where the terms, Close-Ratio and Wide ratio transmissions come into play, with the close ratio usually having less rpm drop during upshifts.


Trans gearing is not the only way to affect the rpm drop when upshifting. Don't you have to account for the overall gear ratio in each gear?

Overall gear ratios w/3.45 rear
1st: 2.68x3.45 = 9.25
2nd: 1.80x3.45 = 6.21
3rd: 1.29x3.45 = 4.45
4th: 1.00x3.45 = 3.45
5th: .75x3.45 = 2.59
6th: .50x3.45 = 1.725

Overall gear ratios w/4.10 rear
1st: 2.68x4.10 = 10.98
2nd: 1.80x4.10 = 7.38
3rd: 1.29x4.10 = 5.29
4th: 1.00x4.10 = 4.10
5th: .75x4.10 = 3.075
6th: .50x4.10 = 2.05

[WVZR-1]

That is what "Hog" is explaining and when he mentions wide or close, he's referring to various transmission builds where the ratios of the internal gears could be or were altered.

The most common early reference to wide and close were the GM/Muncie but you couldn't mix the two. It was either 2.52, 1.88, 1.46 & 1.0 OR 2.20, 1.64, 1.28 & 1.0

There are various manual transmissions where the internals can be mixed and matched. The ZF S6-40 is fixed with no internal options. Wide or close don't apply and shouldn't even be mentioned in a conversation where the ZF is mixed into the conversation.

If you would like to compare the Muncie wide & close use the link I provided and enter the appropriate numbers and it will display exactly what the RPM results of the two would be.

Clint - use my link and enter all of the information for the 3.45, now change that to 4.10 and you'll "see" the results and be able to more easily compare or sort your thoughts. Now if you would like change the tire sizing, you can see that difference also.

The friend ask me to evaluate it for him when using a transmission that is available with multiple internal combinations and I just thought it should make everything a bit easier to understand for everyone when they're considering rear axle ratios because it takes into account the "total drive ratio" right down to including the various tire possibilities. The graph and the MPH/RPM results make the one I linked a bit more understandable.

[PhillipsLT5]

Has been a interesting thread but my bottom line is almost redline in 4th at 1/4 mile & almost redline in 5th at 1 mile, perfect for me with 4.10's

[USAZR1]

Injecting other transmissions into this particular thread is for the most part irrelevant since ZF's and rear gearing are what we're discussing,I thought.

A statement was made that the rpm drop between gears would be the same with either a 3.45 or 4.10 gearset. That is simply false and I can't believe no one else even commented on it.

Just trying to keep misinformation off the site. No gearset is perfect. Both rear ratios are very versatile.

[WVZR-1]

Injecting other transmissions into this particular thread is for the most part irrelevant since ZF's and rear gearing are what we're discussing,I thought.

A statement was made that the rpm drop between gears would be the same with either a 3.45 or 4.10 gearset. That is simply false and I can't believe no one else even commented on it.

Just trying to keep misinformation off the site. No gearset is perfect. Both rear ratios are very versatile.

So long as the shift is made at the same RPM the RPM loss is the same. The MPH changes but the RPM differential is the same.

[USAZR1]

So long as the shift is made at the same RPM the RPM loss is the same. The MPH changes but the RPM differential is the same.

No,it isn't. Take two ZR-1's,one with 3.45's and one w/4.10's,both same tire diameter. Shift both cars into high gear at 80mph. Both cars will drop the same rpm? No,they will not.
At any given speed or gear selected,the 4.10 rear will be spinning the engine faster. Why is that so hard to understand?

[WVZR-1]

No,it isn't. Take two ZR-1's,one with 3.45's and one w/4.10's,both same tire diameter. Shift both cars into high gear at 80mph. Both cars will drop the same rpm? No,they will not.
At any given speed or gear selected,the 4.10 rear will be spinning the engine faster. Why is that so hard to understand?

You're NOW entering a MPH shift into the "mix" - the thread I thought and you mentioned again a couple of times was referenced RPM and if the shift is at the same RPM regardless of the gear the RPM differential remains the same but MPH changes at the RPM being discussed as the result. Tire diameter and axle ratio affect MPH but the RPM drop/spread isn't affected.

The engine and transmission are directly related/connected BUT the rear axle and the tire dimensions skew the results to directly affect MPH.

In this post "ZRXMAX" was in error and "HOG" corrected it and mentioned the only way to alter:

http://zr1.net/forum/showpost.php?p=204372&postcount=102

[USAZR1]

"What we have here,is a failure to communicate." :neutral:

(throwing up my arms) Ok Dave,you win! I give up.

[Jagdpanzer]

"What we have here,is a failure to communicate."

Here is the scene with Paul Newman and Strother Martin and what the Captain actually said:

http://www.youtube.com/watch?v=1fuDDqU6n4o

One of the best movies ever

[WVZR-1]

Clint - I'll leave you with this and if you do this read and still don't understand it's beyond "communication". You need to pay attention to R1 and R2 explanations and maybe it will make better sense to you. Limit your thoughts to "drive-shaft" revolutions which don't change until the axle ratio and tire diameter becomes involved.

http://wahiduddin.net/calc/calc_speed_rpm.htm

Unfortunately every time that axle ratios get involved the formula seems to relate to end MPH and the transmission only controls drive-shaft revolution. Use the calculator that I linked to and use any RPM and change only the rear axle ratio and it will be displayed in a graph and also print. There are several other calculators that do the same thing but don't display the results in an easily understood way to be compared.

If you use my linked calculator and keep the RPM involved at an even thousand it's much easier to compare the MPH effected by the axle ratio and tire dimension. Use 5000 or 6000 or 7000 RPM, change the tire dimension and change the axle ratio to as many variables as you like and I believe you'll see the RPM differential didn't change but MPH changed only in regard to axle ratio and wheel dimensions.

[WVZR-1]

If you would like to see shifts at MPH results you can use this Bonneville Excel spreadsheet and fill in the appropriate information.

http://purplesagetradingpost.com/sumner/bvillecar/SS%206%20Speed%20Excel-1.xls

If there's anything speed related that might interest someone the complete read might be interesting. There are numerous calculators available that are quite interesting for nearly every possible drive combination. Cars bikes whatever!

http://purplesagetradingpost.com/sumner/bvillecar/bonneville-Index.html

[Hog]

No,it isn't. Take two ZR-1's,one with 3.45's and one w/4.10's,both same tire diameter. Shift both cars into high gear at 80mph. Both cars will drop the same rpm? No,they will not.
At any given speed or gear selected,the 4.10 rear will be spinning the engine faster. Why is that so hard to understand?

In an attempt for comprehension as the internet excises 75% of our communication ability. I dont mean to fan any flames here.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxx
You are referencing vehicle speed, when we were talking about engine rpm difference during an upshift.

If you have your 4.10 gear car, and I have my 3.45 rear gear car, in 1st gear you wring your LT5 to 7500rpm, and I wring my LT5 to 7500rpm, we both throw a powershift into 2nd gear. What are out tachometers reading? All else not mentioned in the above scenario equal, our tachs will read the same RPM once our ZF's are in 2nd gear.

RPM drop can only be changed with transmission gear ratio changes. Speed vs engine rpm can be changed via trann gear changes, rear end gear changes and tire diameter changes.

I have never heard "RPM drop" referred to in a fashion to which you have described. To calculate a shift RPM drop, you must 1st have a Before RPM and a Resultant RPM. Shifting a 3.45 vs 4.10 car into high gear at 80mph tells you nothing of rpm drop, but will surely give you the engine rpm of each car, or which, the 4.10 gear car would be revving higher, all else equal. But if you are shifting from 3rd gear to high gear in both cars, the rpm drop in BOTH the 3.45 and 4.10 gear car will be 100% the same.

Quote
At any given speed or gear selected,the 4.10 rear will be spinning the engine faster. Why is that so hard to understand?"

You are describing a difference in overall final drive ratio which combines trans ratios AND trans ratios. Of course the 4.10 geared car will rev higher- all else equal, but this relates to rpm at a speed, not rpm drop as it relates to trans gearing. Regardless of rear gearing, rpm drop during shifts will be 100% the same as trans ratios are the same-all else equal.

[Jagdpanzer]

Similar duscussion on the Viper site
http://www.viperclub.org/howto/faqs/what-are-the-benefits-of-a-rear-gear-swap.php

[XfireZ51]

Whether you have 4.10s or 3:45s, if both cars shift at the same 7000rpm, isn't the rpm drop based on the trans? Closed v Wide ratio trans.

[Paul Workman]

Whether you have 4.10s or 3:45s, if both cars shift at the same 7000rpm, isn't the rpm drop based on the trans? Closed v Wide ratio trans.

You can bet on it. The gear ratios in the trans remain the same w/o regard to what is on the other end of the drive shaft.

[XfireZ51]

You can bet on it. The gear ratios in the trans remain the same w/o regard to what is on the other end of the drive shaft.


so I guess we're done w this discussion.

[Mystic ZR-1]

Are the guts of a Dana 44 the same across applications? I know the housings differ.
In other words, should a competent guy who does Dana 44 work for off road trucks and
Jeeps etc be able to work on a Corvette rear? Key word here is competent...
Contemplating a change to 4.10s.

[WVZR-1]

Are the guts of a Dana 44 the same across applications? I know the housings differ.
In other words, should a competent guy who does Dana 44 work for off road trucks and
Jeeps etc be able to work on a Corvette rear? Key word here is competent...
Contemplating a change to 4.10s.

Yes !

[efnfast]

Are the guts of a Dana 44 the same across applications? I know the housings differ.
In other words, should a competent guy who does Dana 44 work for off road trucks and
Jeeps etc be able to work on a Corvette rear? Key word here is competent...
Contemplating a change to 4.10s.

Really Doug?
I have a guy locally I trust a lot if you're looking for someone.

[Fully Vetted]

Picked up the car yesterday after having the stock 3.45 changed to 4.10 Danas. It appears that I am a victim of my own inflated expectations. After hearing the accolades and reading on this forum a post from a guy who literally said he practically had to "relearn to drive the car" after getting 4.10s, I guess I expected the car to take flight or something. Hmmm, not quite. Yeah, I can tell a small difference but I'd be willing to bet the car is no quicker to a stopwatch, which is kind of a bitter pill to swallow when I just spent $1500 to get "18% more torque to the rear wheels at all engine RPM", according to Marc.

Driving the 2 ratios back to back, I don't feel any 18% torque difference. Not even close. And yes, I did confirm that the stock 3.45s came out of the car. I can say this for sure: if your car is stock or near stock and you're thinking about new gears, DO NOT do anything less than 4.10s. You'd be flushing money down the toilet. Just my 2 cents. :)

So, I just got my car back from Corey who installed 3.90's and I kind of see what you're talking about. I expected this hair on fire experience of having trouble keeping the front wheels on the ground and that's not what happened. However, after a week of driving it and breaking them in now I absolutely love them. It almost felt like the car was slower at first because I was carrying more speed into the 2nd and 3rd shift points and it was noticeable. I got there quicker but I wasn't going as fast. The real beauty of these things though is hitting 3rd gear. That, too me, is where you make up anything you feel you may have lost because this thing hauls the mail now in 3rd and 4th gear. The RPM's are staying right in the meat of the curve and it never ever lets up.

I'm wondering if your impression has changed any now that you've had it a month or so? Mine certainly did.

[XfireZ51]

Smooth cars are fast cars

[Paul Workman]

So, I just got my car back from Corey who installed 3.90's and I kind of see what you're talking about. I expected this hair on fire experience of having trouble keeping the front wheels on the ground and that's not what happened. However, after a week of driving it and breaking them in now I absolutely love them. It almost felt like the car was slower at first because I was carrying more speed into the 2nd and 3rd shift points and it was noticeable. I got there quicker but I wasn't going as fast. The real beauty of these things though is hitting 3rd gear. That, too me, is where you make up anything you feel you may have lost because this thing hauls the mail now in 3rd and 4th gear. The RPM's are staying right in the meat of the curve and it never ever lets up.

I'm wondering if your impression has changed any now that you've had it a month or so? Mine certainly did.

Dittos...

I too find the performance trade-offs interesting, as the advantages between the stock 3.45 vs. 4.10s goes back and forth, depending on what the immediate application is:

Ami's 91 ZR-1 "Turq Monster" with 4.10s has approx 5% more hp than my 3.45 "Phoenix" and the combination of rear gear and brute hp tops my car in the quarter, every time. From the seat of the pants, it is a thrill to drive on the street and on country roads. However, in longer contests, the differences are less obvious.

Case in point:

Bob Banks' ZR-1 and my motors are pretty close, power wise: both @ or near the 510 chp range. However, Bob has 4.10s and I have the stock 3.45s in the rear.

One example does not a trend make, but we ran side-by-side at the last 1/2 mile WANNAGOFAST event last June. What I observed I think might be pertinent to this discussion (my reason for sharing it):

We started from a soft dig: more or less even. However, by the 1/2 way point (quarter mile), Bob had 3 to 3-1/2 lengths on me. I suspect Bob was still in 4th at that point, and had to shift into 5th as I was just shifting into 4th. That is when the gap began to close, and was whittled down to 1-1/2 to 2 lengths at the finish.

In the end, Bob (4.10 gear) crossed the 1/2 mile trap at 138+ mph in 5th and the "Phoenix" with the 3.45s crossed at 144+mph, & still in 4th. However, in spite of gaining on him, he still beat me to the 1/2 mile finish! That initial lead afforded by the 4.10s was too much to overcome, in spite of a significant speed advantage the Phoenix had - at least at the 1/2 mile point.

So, I dunno... Now having opportunity to experience both ratios; 4.10s vs. 3.45s, the each have their place. I like the snap Ami's car has when passing on the highway - and the extra 20-30(?) ponies at the wheels is just the cherry on top. But, I also like that long hard pull my car has to 90ish mph in 2nd gear, following a 5-2 downshift from about 45-50 mph. The 3.45 ratio delivers more torque to the rear wheels (above 75 mph) than the 4.10s do in 3rd, in spite of the 5% hp advantage, and without the additional shift too boot.

So, depending on what or where one likes performance to kick in, moving to a 4.10 ratio might not be "the bee's knees". Having both to compare back and forth makes the distinction much clearer now, and I've cooled to the notion of 4.10s just a little, now that I have that and the 3.45 ratio to compare it with. Maybe 3.73s or 3.90s? And, (to the OP) so it goes....

Paul.

[5ABI VT]

Paul what mph was the 'soft dig' from ? Rolling in 1st?

[XfireZ51]

Paul,

Your results in the 1/2mile mimic how Lee and I ran with VERY similarly modded 92s several years ago at Byron. Lee got to the big end about .3-.4 quicker than me. His 1/8 trap was about 2 mph faster than mine, however I would gain on him in the second 1/8 (not enough to get around him) and our 1/4mile traps were virtually identical. Lee has 4.10s and I had the 3.45s

[KILLSHOTS]

So, I just got my car back from Corey who installed 3.90's and I kind of see what you're talking about. I expected this hair on fire experience of having trouble keeping the front wheels on the ground and that's not what happened. However, after a week of driving it and breaking them in now I absolutely love them. It almost felt like the car was slower at first because I was carrying more speed into the 2nd and 3rd shift points and it was noticeable. I got there quicker but I wasn't going as fast. The real beauty of these things though is hitting 3rd gear. That, too me, is where you make up anything you feel you may have lost because this thing hauls the mail now in 3rd and 4th gear. The RPM's are staying right in the meat of the curve and it never ever lets up.

I'm wondering if your impression has changed any now that you've had it a month or so? Mine certainly did.
Hey David,

Yes, I definitely like them better than I did at first. It sounds like we had similar experiences relative to inflated expectations. Once I came to grips with the fact that I had simply expected too much, I began evaluating the mod more objectively. The car moves away from a stop easier and feels more "drivable" in almost all circumstances. I'm happy with them now. Glad you are too!

[Paul Workman]

Paul what mph was the 'soft dig' from ? Rolling in 1st?

It was a standing start, but with slightly less aggressive rpm and clutch release than typical of a "balls to the walls" quarter mile "ET" contest. This was for top-end primarily: not ET per se'.

[Fully Vetted]

Hey David,

Yes, I definitely like them better than I did at first. It sounds like we had similar experiences relative to inflated expectations. Once I came to grips with the fact that I had simply expected too much, I began evaluating the mod more objectively. The car moves away from a stop easier and feels more "drivable" in almost all circumstances. I'm happy with them now. Glad you are too!

I thought you might be. It feels like the car went on about a 500 lb diet. Very froggy and eager to run.

Paul, I think with modded motors like ours the taller gears are fine. That's why I did 3.90's vs 4.10's. We have the power to pull those tall gears in 1st and 2nd. For the same reason if I added boost I would never do 3.90's or 4.10's. Don't need to. Shorter gears are a great equalizer when you are short on power. IMHO, the more power you have the less gear you need.

[XfireZ51]

I installed 3.73s for mine and when power is transmitted through 19" wheels, acts like a 3.55. I would be tempted to try 3.90s

[Paul Workman]

I thought you might be. It feels like the car went on about a 500 lb diet. Very froggy and eager to run.

Paul, I think with modded motors like ours the taller gears are fine. That's why I did 3.90's vs 4.10's. We have the power to pull those tall gears in 1st and 2nd. For the same reason if I added boost I would never do 3.90's or 4.10's. Don't need to. Shorter gears are a great equalizer when you are short on power. IMHO, the more power you have the less gear you need.

Dave, I have come to agree with much of your (and Dom's) opinion. I too am starting to lean toward the 3.90s as having favor between the 4.10 and 3.90 ratios. Fact is, I just LOVE that 2nd gear/90 mph roll-out...and the resulting look on a few ricer's and LS drivers' faces...priceless! :jawdrop:

[XfireZ51]

Paul,

Just to clarify, I'd consider 3.90's due to the 19" wheels. That would get me to a real world ~3.73. A 4.10 gets me to 3.90s. Having a 3.73 would be a nice compromise gear but its nothing compelling. Not sure it would even be that noticeable. When I had the stock 3.45s, my real gear was about a 3.30.

[Paul Workman]

Paul,

Just to clarify, I'd consider 3.90's due to the 19" wheels. That would get me to a real world ~3.73. A 4.10 gets me to 3.90s. Having a 3.73 would be a nice compromise gear but its nothing compelling. Not sure it would even be that noticeable. When I had the stock 3.45s, my real gear was about a 3.30.

Yep. In your case, Dom, the bigger wheels/diameter would affect the ratios us mortal Z drivers are discussing. It is very easy to factor for your app by d1/d2 x R1*

*where d1 is the distance your new (bigger) wheels cover in one revolution vs. d2 the distance the stock 17" wheel/tire size covers in one revolution, and R1 being the stock 3.45 ratio.

[WVZR-1]

Paul,

Just to clarify, I'd consider 3.90's due to the 19" wheels. That would get me to a real world ~3.73. A 4.10 gets me to 3.90s. Having a 3.73 would be a nice compromise gear but its nothing compelling. Not sure it would even be that noticeable. When I had the stock 3.45s, my real gear was about a 3.30.

You constantly try to mess with the conversation. Your REAL GEAR is what ever the numerical numbers (ring gear/pinion) dictate. Your tire diameters alter your 'final drive' but you constantly fail to mention that. You mention 'real world' - real world is same as 'real gear' - it's the mathematical numbers of the gear set.

19" wheels don't have anything to do with ratio's either and you constantly mention that. There is absolutely no truth to the conversation of yours that I just quoted.

If you want to discuss final drive ratio mention the tire specifications, rear gear and people can maybe relate better.

You might try referring to the tire dimension change as effective ratio and mention the tire dimensions (real measured vs. advertised) and it could more easily be understood. I don't recall you mentioning the tire size but maybe just once, that's the real relevance for comparisons 15", 16" 17" or 20" wheels have no effect on any of it. It's the 'outer circle'.

[tf95ZR1]

This gear ratio discussion has my head (and tires) spinning!
R R R
;)

[Kevin]

lets play nice gentlemen

[PhillipsLT5]

This gear ratio discussion has my head (and tires) spinning!
R R R
;)

Anyone can tell me anything, BUT I will go with 4.10's over 3.45 in any car any day, Just sayin

[mike100]

It is so difficult to put the mathematics into words, but many of us know what the final drive and tire diameter do to the car as a whole. I have been told by two different people that 3.73's really woke up their ZR-1's that they used to own. These comments were unsolicited and just came up as advice for bang-for-buck mods. I also like this idea as there is a speedo gear available for this ratio for a clean conversion. Unfortunately I'm pretty much done with projects and I'm just keeping the car in good condition at this point, but it would be the next thing on the list if the budget was available.

[Paul Workman]

You constantly try to mess with the conversation. Your REAL GEAR is what ever the numerical numbers (ring gear/pinion) dictate. Your tire diameters alter your 'final drive' but you constantly fail to mention that. You mention 'real world' - real world is same as 'real gear' - it's the mathematical numbers of the gear set....*.

OUCH!

In spite of perhaps using less than precise or exacting terminology, I think most of us understand what Dom was trying to get at. And, he brings a valid point: whatever conclusions or direction this thread makes or takes, tire diameter variances introduced by those that have other than the "normal" tire sizes need to be considered. (OK, he only mentions wheels, but we know what he's implying, I believe.)

Just sayin....

Paul.

[XfireZ51]

WV,

Apologies for my lack of precision. Took too much for granted. If anyone else in this thread was thrown into a technical tizzy along w WV, please allow me to apologize to you also. Precisely. :o

[USAZR1]

I installed 3.73s for mine and when power is transmitted through 19" wheels, acts like a 3.55. I would be tempted to try 3.90s


And our car has even taller rear tires than Dom,although not by a whole lot. Our 94 has 335/30/19 rears with 4.10 cogs. I like it.

No apology needed on this end,Dom. I understood completely what you were trying to say.

[WVZR-1]

Some 'real' information I believe. Dominic, I'll use your ratio and tires as an example. If you had 3.73 gears and your 315/35R17 tires and were 'happy' you need to be concerned about not your losses but rather what you need to do to compensate for the increased tire that you added or you just disregard it and don't worry.

I'll use that for a start. I picked a MPH # because one is need to start from so I chose 60 MPH and 4th gear. I always use 1:1 regardless of the transmission. A 3.73 @ 60 MPH I got 2960 RPM by this:

60 X 3.73 X 336/25.4 (the 25.4 I used from a dimension I measured with my BFG 315/35R17's many years ago) I did NOT use the advertised diameter. That skews the results which BTW I believe the charts earlier in this thread are based off advertised numbers and not real dimensions that we can measure. Those #'s are close but NOT correct.

Now when you add the tire that you mention measuring 26.25 (in this thread) I get an RPM value of 2864:

60 X 3.73 X 336/26.25

Now to get your 'performance' back you need to add gear and since we know the various ratios available for the D44-HD it's easier to experiment using available ratios substituted into the formula.

60 X 3.90 X 336/26.25 = 2995 so you've got it all back with that gear change + very few RPMs.

If a person had 4.10's with 315/35R17 and was 'happy' then these #'s if they made the same tire change would be required.

60 X 4.10 X 336/25.4 = 3254 RPM (315's)

60 X 4.10 X 336/26.25 = 3148 RPM (26.25 measured)

The add required using available ratios:

60 X 4.30 X336/26.25 = 3302 so you've got it all back again + a few more RPMs.

These were very straight forward and it's much easier using 'known' available ratios to calculate recovery.

With your particular tire choice the 'loss' if you wanted to only be concerned with the loss is 3%. 25.4/26.25 = .96761 so the 3.45 becomes 3.34 and the 3.73 would become 3.61 or so.

Done in this fashion also to calculate the new ratio 25.4 (original tire) X 3.73 (axle ratio)/ 26.25 (new tire) = 3.6092

You could confirm those numbers I'd think by checking RPMs with an accurate tach and not the cluster component.

Every tire needs to be measured at the pressures you will intend to use and dimensions will vary for various brands.

I believe my math will stand the test. I hope or I've made a much larger A$$ of myself. There are calculators out there that likely will confirm these numbers or very close. The one I posted way back in this thread should work I believe.

This is where I got the dimensions that I used for your 19's.

I have 19s on the back. The fronts are 18s. Just measured the rears sitting there w ~ 35psi, they stand at 26.25". Size is 325/30/19. These are the Nitto Invos which I like quite a bit. Good wet, fairly quiet, and grab pretty well on hard shifts.

[Dynomite]

When you boys are talking gear ratios to determine vehicle speed.........you should use Tire Deflected Radius.....which by the way varies with tire rotation speed just a bit. And obviously varies with tire inflation pressure. Tire Deflected Radius is the distance from the center of the wheel to the pavement.

Tech Info - ZR1 Differential Gearing and Vehicle Speed Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660569)

Some more Calculations for you as your interests vary ;)

CALCULATION METHODS
1/4 mile Calculator TIPS (http://vexer.com/automotive-tools/1-4-mile-ET-HP-MPH-calculator)
Gear calculator TIPS (http://vexer.com/automotive-tools/speed-rpm-calculator)
Wheel Offset Calculator (http://www.1010tires.com/WheelOffsetCalculator.asp)
Automotive Calculators (http://www.wallaceracing.com/Calculators.htm)
Tech Info - LT5 Horsepower and Torque Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660568)
Tech Info - ZR1 Differential Gearing and Vehicle Speed Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660569)
Tech Info - ZR1 Wind Force, Rolling Resistance, Drivetrain Loss Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660570)
Tech Info - LT5 Camshaft Timing Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660573)
Tech Info - LT5 Pressure Drop In Oil Lines Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660575)
Tech Info - LT5 RC SL4-205 injectors (500+ hp) Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660578)
Tech Info - LT5 Summary of Camshaft Timing from Start to Finish (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660580)
Tech Info - LT5 Timing Diagrams (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660582)
Tech Info - L98 Frisbee Horsepower (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660586)
Tech Info - LT5 Coolant Flow Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660591)

[WVZR-1]

I thought I'd keep this in a different post but you should be able to calculate your actual tire diameter using a formula also OR maybe just use it to confirm your measurements. Tach would need to be very accurate.

MPH X gear ratio X 336 / RPM

In the above 60 MPH X 3.45 X 336 / 2960 = 25.4 (a match to what I measured years ago) and Dominic's 60 X 3.73 X 336 / 2864 = 26.25 (what Dominic mentioned measuring)

Clint, you could use this formula with your tires already mounted and measure to confirm.

Cliff - I'm guessing my numbers maybe passed your test.

[Hog]

Just some general observations about the last couple pages

After a few burnouts all these numbers go out the window, esp. on soft tires. Then factor in tire growth due to the centripetal/centrifugal force changes at speed, tire pressure while driving, the effects of wheel alignment on tire heating, type of gas the tire is inflated, plus the manufacturing tolerances of the tires themselves, even tread squirm could be thrown into the convo.

This why there is a "fudge factor" built into any modern ABS or stability system. Accuracy has its place.

IMO If you are going to go through the trouble of a ring/pinion change, you might as well make it worthwhile.

The usual course of engine modification will move the power/torque corves to the right oi the graph, with highly modified engine making less torque at lower rpms. This would necessitate lower gearing to allow for driving below the torque.
More power=more revs(N/A)=more gear (all else equal)

[Paul Workman]

Some 'real' information I believe. Dominic, I'll use your ratio and tires as an example. If you had 3.73 gears and your 315/35R17 tires and were 'happy' you need to be concerned about not your losses but rather what you need to do to compensate for the increased tire that you added or you just disregard it and don't worry.

I'll use that for a start. I picked a MPH # because one is need to start from so I chose 60 MPH and 4th gear. I always use 1:1 regardless of the transmission. A 3.73 @ 60 MPH I got 2960 RPM by this:

60 X 3.73 X 336/25.4 (the 25.4 I used from a dimension I measured with my BFG 315/35R17's many years ago) I did NOT use the advertised diameter. That skews the results which BTW I believe the charts earlier in this thread are based off advertised numbers and not real dimensions that we can measure. Those #'s are close but NOT correct.

Now when you add the tire that you mention measuring 26.25 (in this thread) I get an RPM value of 2864:

60 X 3.73 X 336/26.25

Now to get your 'performance' back you need to add gear and since we know the various ratios available for the D44-HD it's easier to experiment using available ratios substituted into the formula.

60 X 3.90 X 336/26.25 = 2995 so you've got it all back with that gear change + very few RPMs.

If a person had 4.10's with 315/35R17 and was 'happy' then these #'s if they made the same tire change would be required.

60 X 4.10 X 336/25.4 = 3254 RPM (315's)

60 X 4.10 X 336/26.25 = 3148 RPM (26.25 measured)

The add required using available ratios:

60 X 4.30 X336/26.25 = 3302 so you've got it all back again + a few more RPMs.

These were very straight forward and it's much easier using 'known' available ratios to calculate recovery.

With your particular tire choice the 'loss' if you wanted to only be concerned with the loss is 3%. 25.4/26.25 = .96761 so the 3.45 becomes 3.34 and the 3.73 would become 3.61 or so.

Done in this fashion also to calculate the new ratio 25.4 (original tire) X 3.73 (axle ratio)/ 26.25 (new tire) = 3.6092

You could confirm those numbers I'd think by checking RPMs with an accurate tach and not the cluster component.

Every tire needs to be measured at the pressures you will intend to use and dimensions will vary for various brands.

I believe my math will stand the test. I hope or I've made a much larger A$$ of myself. There are calculators out there that likely will confirm these numbers or very close. The one I posted way back in this thread should work I believe.

This is where I got the dimensions that I used for your 19's.

_________________

Yikes!

"If you can't explain it simply, you don't understand it well enough." - Albert Einstein

(This discussion has veered off-topic, but since we're here now...)

Ratios.

No matter how you slice it, the root to questions regarding the effect on differential gears, speed, rpm, or any other equivalents resides in the ratio of one tire size to the other. Period.

Depending on the question, there may be a direct ratio relationship, or an inverse (i.e, 1/ratio) relationship, but regardless, that ratio between tire sizes permeates all calculations regarding differences in gear ratios, or distance covered per tire rotation, or rpm, or you name it.

For example: If speed over the ground and engine rpm are to remain constant, then the differential reduction ratio (ring/pinion) must be changed by the same ratio as that between the two tires. Otherwise, either speed over the ground will change for a given motor RPM, or RPM will change for a given speed.

Or, for an opposite example, to find the equivalent differential reduction ratio value resulting from a change of tire size, the inverse (1/RATIO) x differential reduction gear ratio will produce the effective equivalent rear end gear ratio (as well as the ratio correction required for the new speedo gear.

And, so it goes... (Well, almost. Practical applications typically have dynamic variables which skew results. Variables like Hog points out and many other practical bits and pieces get in to increase the ambiguity factor. But, as long as we can account for some of of the small dribbs and drabbs, and the ambiguity doesn't exceed say 5%, it should suffice for purpose of discussion, I should think.)

Hog: Good points as well.

But back to the OP's question: What are the real trade-offs between say the 4.10s vs. stock 3.45s in actual driving or racing situations??


:cheers:

WV: I must be staring right at it but do not see: where is that "336" factor you use in your calc's derived from?

[XfireZ51]

Dave,

Actually we had a very similar thread several years ago here for anyone interested in referring back to it.

http://zr1.net/forum/showthread.php?t=15674&highlight=Rear+axle+ratio

And I in fact did what you suggested, which was to use the stock 3.45 trans gear
With the 3.73 rear gear. Based on my GPS v Speedo, I get ~ 4% error! with the speedo reading slower. Good enough for cruising. Some of the specs are in that thread.

[WVZR-1]

_________________


WV: I must be staring right at it but do not see: where is that "336" factor you use in your calc's derived from?

Why the 'fine print?

I've used the 336 number for years and I don't know where I got the formula for it originally but there's explanations and the formula scattered about of all places "The Internet".

I found this explanation since you asked your question and it seems pretty concise and easily understood too, I'll just post the link. I believe it should work. Regarding explaining it 'simply'? I thought I did. Understanding it? Yes I do.

There are calculators that are used by many that aren't accurate and I just displayed my math, that doesn't have anything to do with understanding or simply. There are some RPM/MPH charts in this thread and all use 'advertised' tire specifications and not a 'loaded radius' it appears. I couldn't make the numbers match unless I used the 'advertised' dimensions.

http://www.numericana.com/answer/formula.htm#carspeed

[WVZR-1]

Dave,

Actually we had a very similar thread several years ago here for anyone interested in referring back to it.

http://zr1.net/forum/showthread.php?t=15674&highlight=Rear+axle+ratio

And I in fact did what you suggested, which was to use the stock 3.45 trans gear
With the 3.73 rear gear. Based on my GPS v Speedo, I get ~ 4% error! with the speedo reading slower. Good enough for cruising. Some of the specs are in that thread.

I recall bits of that and I mentioned a couple calculators in that thread because it seemed at the time it was easier for people to understand rather than doing the math on responses to avoid responses similar to Paul's. It appears to be complicated but after a few goes at them it's not that difficult.

I did speedometer calibrations for people to take to court and attempt to get fines and charges reduced to improper equipment etc. back in the day. I had to 'introduce' the error that we're attempting to correct these days. I don't recall any of my calibrations failing the person except a couple occasions where the person asked for an error that just wasn't likely accomplished.

I did the calibration, the buyer went to an approved certification station and of course there was an error, the person reinstalled the correct parts OR we actually corrected the error, the person returned to the certification station they certified the correction and the receipt for services went to court. Charges usually dismissed, occasionally if the JP/Judge suspected the tampering there was an improper equipment citation issued which had no points and a very low fine.

All the math was done on paper and changes sometimes by trial and error.

[Fully Vetted]

"If you can't explain it simply, you don't understand it well enough." - Albert Einstein

LMAO. That's funny...

I did go from the stock 17' A molds to an 18" Shelby but I made sure the overall diameter was the same (or at least very close). I've always assumed that was a determining factor. I guess I was right...

[Harvie]

Our testing, years ago, with a modified ZF trans gears (to keep the drop between shifts in the engines peak power band) and with higher horsepower engines the 391 ratio was the one that got to the finish line first.

We attempted to get the trans ratios to where we had five gears instead of 4 plus 2 overdrives, that worked real well. REEEEEEAL EXPENSIVE

Look up Gforce and look at the transmission ratios Leo makes for an example of what can be done to the ZF it money is no problem.

[Paul Workman]

Our testing, years ago, with a modified ZF trans gears (to keep the drop between shifts in the engines peak power band) and with higher horsepower engines the 391 ratio was the one that got to the finish line first.

We attempted to get the trans ratios to where we had five gears instead of 4 plus 2 overdrives, that worked real well. REEEEEEAL EXPENSIVE

Look up Gforce and look at the transmission ratios Leo makes for an example of
what can be done to the ZF it money is no problem.

Harvie,
Did that test include stock 375 or 405 hp or (??) cars?

Paul.

[Harvie]

Harvie,
Did that test include stock 375 or 405 hp or (??) cars?

Paul.

To quote the moderator

No I "hacked up" everything and motor I played with, christ my lt1 70 car (350-370hp stock) had a 425 hp small block so I thought the lt5 GM hp numbers were pathetic, the 650 number Lotus had made me curious.

We just never cut a hood open inorder to straighten out the intake air flow to get to their numbers. Did everything else, though.

[Paul Workman]

To quote the moderator

No I "hacked up" everything and motor I played with, christ my lt1 70 car (350-370hp stock) had a 425 hp small block so I thought the lt5 GM hp numbers were pathetic, the 650 number Lotus had made me curious.

We just never cut a hood open inorder to straighten out the intake air flow to get to their numbers. Did everything else, though.

Um, yeah...425 hp NET or GROSS?

[Harvie]

Um, yeah...425 hp NET or GROSS?

All the HP figures are from the same dyno, min of 5 pulls. We tested a straight out of a car LT5 and got max between 372-380HP and the 1970 based full roller motor LT1 at 423-428HP. Both GM 350 small block engines.

We always started with baseline runs to see how much GM fudged the numbers for insurance purposes. Common practice...

So I would call those numbers for both engines net at the flywheels.

When the ZR1s were introduced the LT5 option alone was $35,000.00 and there were no aftermarket engine parts for the LT5.

I still have one of the first sets of JLs lightweight pistons in my cabinet. I have I believe 2 different sets of cams because we were testing for max lift limits/spring pressure ranges. Airflow was always the restriction that limited the output.

When I started fooling around with them Lingenfelter charged $16,000 to build a motor from a new engine and Calloway was at $14,500.00.

Now guys buy their entire cars for that.

I always wonder how many of the current owners would have one, then try and modify it, if they had to pay 80K for them. even in the lower current usds.

[Kevin]

Did callaway charge you extra because you spell their name wrong?

[Harvie]

Did callaway charge you extra because you spell their name wrong?

Driving back and forth from New Lime CT to drop off/pick up the motor was fun but, no they gave me a discount becaue it only lasted about 400 miles before it needed rebuilding.

You buy a motor from them also or just curious?

Oh I forgot, that would be hacking up your car, sorry for asking....mate

[Kevin]

Driving back and forth from New Lime CT to drop off/pick up the motor was fun but, no they gave me a discount becaue it only lasted about 400 miles before it needed rebuilding.

You buy a motor from them also or just curious?

Oh I forgot, that would be hacking up your car, sorry for asking....mate

Didn't buy anything from them, too broke to. m8

[Bob Eyres]

Picked up the car yesterday after having the stock 3.45 changed to 4.10 Danas. It appears that I am a victim of my own inflated expectations. After hearing the accolades and reading on this forum a post from a guy who literally said he practically had to "relearn to drive the car" after getting 4.10s, I guess I expected the car to take flight or something. Hmmm, not quite. Yeah, I can tell a small difference but I'd be willing to bet the car is no quicker to a stopwatch, which is kind of a bitter pill to swallow when I just spent $1500 to get "18% more torque to the rear wheels at all engine RPM", according to Marc.

Driving the 2 ratios back to back, I don't feel any 18% torque difference. Not even close. And yes, I did confirm that the stock 3.45s came out of the car. I can say this for sure: if your car is stock or near stock and you're thinking about new gears, DO NOT do anything less than 4.10s. You'd be flushing money down the toilet. Just my 2 cents. :)

It's interesting to look back at the months of discussion about the minutia of gear ration selection and tire sizes, and see that Chris is right. And that his final assessment, that 4.10 gears are the minimum numerical change recommended for noticeable performance improvement in a stock, or near stock, ZR-1, hold up pretty well.

[ZR1North]

I've read this threat several times. Thanks for starting it, Chris, and for everyone for the usual informative contributions. Now, for something a little different....

I'll start with my reason for adding - I have a whole new respect for the economy-performance balance of our ZR-1s having just driven my '16 Z06 from Michigan to Florida to extend its use when I am there on-and-off over the winter (gotta get some miles on it while warranty is still in effect).

My '91 ZR-1 has 4:10s and Marc's 510 pkg (sans the SM flywheel, so it's really 490hp). My first drive with the pkg. was Mountain Run 2015, and I noticed two key things - 1) having the 4:10s made the run through the mountains a whole lot better than what I experienced road racing it previously with the 3:45s (to Paul Workman's point in an earlier post); 2) having a useful 6th gear on the freeway made cruising a great experience from a drivability and economy perspective (I made 24 MPG highway on the trip) running @ 75MPH revving at 2K RPM. I found that I was able to accelerate around traffic in 6th quite easily; previously I was constantly downshifting to 5th to do so.

Fast forward to my trip this weekend in the Z06. After I got 1,000 miles on it, I started to experiment with various modes. I noticed that when I switched it to "Eco" mode and the computer switched the engine to "V4" for fuel economy, I was getting about 34 MPG, but that was only on flat surfaces running @ 75 MPH in 7th gear on cruise (RPM were 1,500). When I encountered a grade, it switched to "V8" mode and the MPG dropped to 22-29 range (instantaneous computer calculations). Overall, I averaged 27 MPG, mostly in 7th gear @ 1,500. When I shifted to 6th for passing, RPM jumped to 2,000, but acceleration in 6th was unlike anything I've experienced in anything else I've driven. For comparison, gear ratios in the Z06's Tremec gearbox are: 1st, 2.97; 2nd, 2.07; 3rd, 1.43; 4th, 1.00; 5th .71; 6th, .57; 7th, .48; final drive is 3:42. This compares to our Zees with: 1st, 2.68; 2nd, 1.80; 3rd, 1.29; 4th, 1.0; 5th, .75; 6th, .5 - my final drive now is 4:10.

All that to say, even with 30 years of technological advancement, our Zees are still pretty respectable in terms of performance and economy when upgraded. As for the 4:10 vs "other ratios", I wouldn't change my decision to switch to the 4:10s, but I am more of a road racer than a drag racer. I ran the NCM track in May, and as with the MR in 2015, I found the combination fantastic on both the slow corners and fast straightaways. I think it's a great combination for highway and road racing and while I haven't drag raced the car, I think what I've read here would not cause me to change from the 4:10 for the odd drag run.

FANTASTIC THREAD!

Bob