Transverse leaf spring question

[secondchance]

Are early (90-92?) and later (93-95) leaf spring rates the same and interchangeable?
I am dropping the car height a bit so I picked up a front spring from another WAZOO member and glued on the wedges. However, Phil noticed end plates (both ends where it sits above the lower A arms) are a bit diffrent from the later cars.
So 2 questions - any rate difference? Will the ends work with a 94?

Thanks.

[mike100]

There's a spring rate chart out there in cyberspace somewhere that lists the spring(s) for each year. What color is the little square on the top of the spring? blue-ish green? There were 3 different color codes for the coupe, vert, and zr-1 for the early cars and is referenced in the manual. I would have to look at the 95 manual i also own, but I'm thinking it is the same.

[Scrrem]

Here's one chart I found on spring rates...

http://www.wedophones.com/Manuals/Chevrolet/Corvette/1984-1996%20C4%20Corvette%20Suspension%20Tuning%20Chart .pdf

Rich

[secondchance]

Here's one chart I found on spring rates...

http://www.wedophones.com/Manuals/Chevrolet/Corvette/1984-1996%20C4%20Corvette%20Suspension%20Tuning%20Chart .pdf

Rich

Thanks Rich.

[secondchance]

There's a spring rate chart out there in cyberspace somewhere that lists the spring(s) for each year. What color is the little square on the top of the spring? blue-ish green? There were 3 different color codes for the coupe, vert, and zr-1 for the early cars and is referenced in the manual. I would have to look at the 95 manual i also own, but I'm thinking it is the same.

I'm positive 91 came from a 91 Z. I'll check the color code when I get home later.

[secondchance]

Good thing I checked this.
91 sping for ZR-1 is 96.2 N/mm (548 lbs/inch) -front and 39.9 N/mm (228 lbs/inch) - rear.
92 and later are 75.4 (430 lbs/inch) and 33 (188 lbs/inch) respectively.

I'm gonna have to remove my front, shave off the factory bumpers and reglue lowering wedges.

[WVZR-1]

Are early (90-92?) and later (93-95) leaf spring rates the same and interchangeable?
I am dropping the car height a bit so I picked up a front spring from another WAZOO member and glued on the wedges. However, Phil noticed end plates (both ends where it sits above the lower A arms) are a bit diffrent from the later cars.
So 2 questions - any rate difference? Will the ends work with a 94?

Thanks.

The springs are assembled differently on the control-arm ends. Your springs should have had a 1 1/4" square pedestal so to speak rather than just the rubber molded insulator like the '91 that you purchased.

You should have no issues. If the heights are different in the FSM then there will be differences.

Forgot I have a '94 FSM so:

I checked a '91 FSM and a '94 FSM and the datum line measurements are different with the '91 being less. I checked the reference for C height. Now the image is a bit different but certainly the point isn't. Look at 10-3-2 or 3 in your FSM and look at the datum heights. A '91 @ C is 177mm and a '94 @ C is 192mm. That's pretty close to the difference in the spring height for the two. You might end up a little lower than you intended!

Good thing I checked this.
91 sping for ZR-1 is 96.2 N/mm (548 lbs/inch) -front and 39.9 N/mm (228 lbs/inch) - rear.
92 and later are 75.4 (430 lbs/inch) and 33 (188 lbs/inch) respectively.

I'm gonna have to remove my front, shave off the factory bumpers and reglue lowering wedges.

I would be tempted to use the '91 if time and the aggravation doesn't bother you should you need to redo the procedure later. I'd think the increased spring rate maybe a +.

[secondchance]

The springs are assembled differently on the control-arm ends but carry the same codes. Your springs should have had a 1 1/4" square pedestal so to speak rather than just the rubber molded insulator like the '91 that you purchased.

You should have no issues. If the heights are different in the FSM then there will be differences.

Forgot I have a '94 FSM so:

I checked a '91 FSM and a '94 FSM and the datum line measurements are different with the '91 being less. I checked the reference for C height. Now the image is a bit different but certainly the point isn't. Look at 10-3-2 or 3 in your FSM and look at the datum heights. A '91 @ C is 177mm and a '94 @ C is 192mm. That's pretty close to the difference in the spring height for the two. You might end up a little lower than you intended!

Hi, David,

Looks like I need to rework my spring. Rates are different between 91s and 92+ cars.

[Scrrem]

If you looking to sell that spring, I'd be in the market ;)
Rich

[WVZR-1]

Hi, David,

Looks like I need to rework my spring. Rates are different between 91s and 92+ cars.

Like I added to my other post. I believe the spring rate could be a +!

[secondchance]

If you looking to sell that spring, I'd be in the market ;)
Rich

Which one? Early or later one.

[secondchance]

Like I added to my other post. I believe the spring rate could be a +!

I hear you David. If I go with early front (stiffer) the shouldn't I replace rear w/ early also (stiffer). Otherwise, I could be introducing oversteer (or did I get it backwards)?
Also, do you think Chevy engineers respecified shocks in compression/rebound when they went to softer springs? I wonder if they stiffened up the shocks to counter softer spring somewhat...

[Scrrem]

Which one? Early or later one.

The early one.
Rich

[secondchance]

The early one.
Rich

Well, let's see how it goes.
I need to find out shock difference. Having stiffer springs front and back (and I know where to find a matching rear) may reduce scraping my front airdams. On the other hand, if the early cars had stiffer shocks then I would have to revalve my shocks to work with stiffer springs. Need to think this thru... If I stay with later springs, you have the first dib on 91 front.

[Scrrem]

Well, let's see how it goes.
I need to find out shock difference. Having stiffer springs front and back (and I know where to find a matching rear) may reduce scraping my front airdams. On the other hand, if the early cars had stiffer shocks then I would have to revalve my shocks to work with stiffer springs. Need to think this thru... If I stay with later springs, you have the first dib on 91 front.
Cool. Yeah, I did research on this subject a few years ago and got really confused when you start combining the different options, FX3, Z51, ZR-1 and all seem to have different spring rates and the rate changes from year to year. This in my mind, must change the shock dampening value. Way too complex for me to try to de-cypher.
Rich

[secondchance]

In summary, 90-91 had stiffer springs but softer shocks. 92-95s had softer springs with stiffer/faster shocks.

For those who are interested, article w/ link below is very interesting read:
http://www.corvetteactioncenter.com/tech/c4/fx3/index.html

Site Administrator - If I am breaking the forum rule by the above link, please edit.

[WVZR-1]

In summary, 90-91 had stiffer springs but softer shocks. 92-95s had softer springs with stiffer/faster shocks.

For those who are interested, article w/ link below is very interesting read:
http://www.corvetteactioncenter.com/tech/c4/fx3/index.html

Site Administrator - If I am breaking the forum rule by the above link, please edit.

It's an interesting read but then you need to consider the source. Halverson - oh well! He publishes what he's paid to publish.

It still doesn't negate the possible + to the increased spring rate. Halverson's #'s for his suspension parts are numbers he was supplied with from production specifications, you don't think there were manufacturing tolerances? A '91 spring is 23 or 24 years old and your ''94 spring is just a couple years younger maybe. If you want to know what the '91 spring actually is "NOW" get it checked! Answers maybe all of your questions.

I believe it's being way "over thought" - had the later spring not had the pedestal type cushion at the control arms you would have had the job "done" and been telling us about the things you really enjoyed about the change.

[batchman]

My two cents - if you lower you want more spring rate to minimize running out of travel.

I *think* any factory-spec shock should work with any factory spring rate, while it won't be optimum it should work for street driving. The more aggressive the driving the further from optimum it will become. Worst that should happen is back shocks may not fully control rear spring rate and you get an "echo" or hobby-horse effect.

FWIW I went from stock 91 to 750/375 (front/rear) and it ain't enough for autocross on slicks - next stop coming soon (I hope) is 1k/500 with Penske double adjustables.

Cheers,
- Jeff

[mike100]

when you cut the bushings and/or remove the shims, you effectively lower the spring rate so you might be better off with the early spring. Another way to put it is you reduce the spring preload so the car sits lower. you probably don't approach the stock tension until you are near the bumpstops. Doing the lowering wedges makes the car softer imo.

You might consider taking out one or both bushing shims as that will get you some drop without having to remove the spring 100% (it is easier and about 2/3rds the work). The ZR-1 (early cars at least) has two shims presumably due to the weight of the LT5, whereas the coupe/vert came with just a single shim or no shim.

[mike100]

The ZR-1 front spring color code is green- it's a square ink spot on the top face near the end.

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC03736.jpg~original

recently completed: stock spring back in because I couldn't stand dragging the car over speed bumps any longer- control arm out because nobody owns the special transverse leaf compression tool.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/monoleaf_sm_zpsc8fa8767.jpg~original

[mike100]

Here's what the shims look like when not installed above the spring bushing. my car was slammed and the two aluminum shims are shown here going along for the ride (at least they didn't toss them).

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC03734.jpg~original

[WVZR-1]

I checked two springs I have here, a '91 removed at 16K from a ZR-1 with the "green ink" and a code of FHA with the molded pad as in Mike's image. I have another from a '93 that is assembled with the riveted on metal reinforcement and the 1 1/4" square pedestal cushion like I believe all '92+ cars are assembled with and they both have the same FHA code. That tells me the spring rate is the same and if there are differences in any of the publicized specifications then the assembly procedure at the control arm ends is responsible for that variance.

Mike - What are the actual codes stamped/molded/branded in your two springs?

The code can be checked from underneath easily, it should be maybe 2 - 4" inboard of the control arm contact area.

[mike100]

I'm away from my car until the end of the week, but I do remember the stamped code matching from one spring to the other when Erik(YZpilot) and I swapped.

[secondchance]

WVZR-1,

'91 @ C is 177mm and a '94 @ C is 192mm"
Am I understanding correct that end of spring rubber pad (90-91) vs. later cars w/ puck results in later cars sitting 15mm (about 9/16") taller?

[WVZR-1]

WVZR-1,

'91 @ C is 177mm and a '94 @ C is 192mm"
Am I understanding correct that end of spring rubber pad (90-91) vs. later cars w/ puck results in later cars sitting 15mm (about 9/16") taller?

The description of the measuring point matches for C in both charts. The balance of the datum reference points change from '91 to '94 so the comparisons can't be compared.

The math substantiates your deduction. If though the '92+ spring is assembled with the "puck" then that would seem to negate that thought because the '92 FSM mentions the 177mm @ C.

There's no doubt that it's somewhat confusing.

[secondchance]

Yes. It is very confusing.

[USAZR1]

when you cut the bushings and/or remove the shims, you effectively lower the spring rate so you might be better off with the early spring. Another way to put it is you reduce the spring preload so the car sits lower. you probably don't approach the stock tension until you are near the bumpstops. Doing the lowering wedges makes the car softer imo.

You might consider taking out one or both bushing shims as that will get you some drop without having to remove the spring 100% (it is easier and about 2/3rds the work). The ZR-1 (early cars at least) has two shims presumably due to the weight of the LT5, whereas the coupe/vert came with just a single shim or no shim.


Sorry for bumping this thread back to the top but I haven't heard the results of Yun's changes and what changes he settled on with his car. I want to lower our 94 1.5"-2" without having to install coilovers. Have talked with Vette Brakes & Products about one of their adjustable front springs like Jeff Moore has on his 91 ZR-1. Only possible downside I can see with one is the 900-1K spring rate but the ability to adjust the ride as easily as a C5 is a bonus.

Mike,can you post a photo of the bushing shims you're referring to in the above post?

[secondchance]

Sorry for bumping this thread back to the top but I haven't heard the results of Yun's changes and what changes he settled on with his car. I want to lower our 94 1.5"-2" without having to install coilovers. Have talked with Vette Brakes & Products about one of their adjustable front springs like Jeff Flint has on his 91 ZR-1. Only possible downside I can see with one is the 900-1K spring rate but the ability to adjust the ride as easily as a C5 is a bonus.

Mike,can you post a photo of the bushing shims you're referring to in the above post?

I will be installing a pair from 91, front with shaved wedges, after engine is reinstalled.

[mike100]

the two shims are actually shown in the last photo I posted. they are riding under the bracket and sandwiched together. They are supposed to be on top of the spring- at least the PO didn't throw them out. they are just flat aluminum stock- You could make replacements easily. On the previous page, one is also shown next to the blue floorjack wheel on that pic.

[Hib Halverson]

It's an interesting read but then you need to consider the source. Halverson - oh well! He publishes what he's paid to publish.

Actually, I was not paid for that article on the CAC web site. I decided what was published and am responsible for it's accuracy.

"WVZR-1", if you're aware of any incorrect information in that article, so I can correct any mistakes, please post the errors and your documentation to support them.

But even if I was paid for it–let me ask you "WVZR-1"–in your opinion, how would that impact the credibility of the content?

It still doesn't negate the possible + to the increased spring rate. Halverson's #'s for his suspension parts are numbers he was supplied with from production specifications, you don't think there were manufacturing tolerances?

There were, indeed, "manufacturing tolerances". In fact, the tolerances were so large that, during the earlier C4 years, frustrated with chronic differences in trim heights of cars with the same springs, GM finally divided each spring into three "groups". Then it developed the spring shims one finds on the front and rear spring mounts.

The spring suppliers were required to categorize each spring which met the initial specifications into three groups. Some were right at the specified spring rate, some were a bit below and some were a tiny bit above. The spring group determined the number of shims (ft.) or the location of the shims (rr). This system allowed the assembly plant to have all the cars much closer in trim height and was used for the rest of the C4 production.

Obviously, in the front, the ideal sitch is a car with 2 shims because pulling the shims out lowers the car by about 1/2-in.. In the rear a car with 2 shims above the rear spring is desireable because if you move the shims to below the spring you lower it in the rear by about 1/2-in.

[USAZR1]

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

[mike100]

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

I consider 1/2" a decent drop. You could try flipping the shims to the outside and try it out without altering the bushing permanently (allowing you to go back). Technically you aren't changing the spring rate...just effectively changing the rate by unspringing it some with the initial tension being softer.

I think you get the idea from the way you replied, but I would offer that the shock stiffness on the front end of a c4 seems more critical to me than the spring- even on the ZR-1.

There seems to be only 5 options on transverse springs (for the front):
1) stock
2) stock bushing with shim(s) removed (less drop)
3) lowering wedge with shims
4) lowering wedge with no shims (slammed -->don't do it- cars is dangerously low and close to bumpstops. Also a gap between spring and frame when car is jacked up).
5) VB&P adjustable spring; this is much lower and even the taller setting is probably well into lowered ride height territory. Advantage is high spring rate for heavy LT5 and you don't need the special GM spring tool or have to remove an A-arm to install because it sits flat at rest (quick and easy install).

[Hib Halverson]

VB&P told me they manufacture at least five springs at a time and that every one will have a different rate.

If removing both front shims only drops the front ride height 1/2" and will also lower the spring rate of an already soft spring,I probably should look at other lowering options for our 94.

While I lack the equipment to measure spring rates, I suspect that the difference in rates is not great enough to have an appreciable effect on handing but it is enough to have make a differenct in trim height. Also, it's possible that the degree to which the spring is arched may also play into this.

All I know if my 95 came with blue dot springs on both ends so I took all the shims out of the front and, and in the rear, moved all the shims to the bottom and got the car lower but not so low that I lack ride travel.

[USAZR1]

Thanks for the input,Mike & Hib. For starters,I'll probably remove the front shims and install longer bolts in the rear. The new 19" tires are about 3/4" or so taller so that will close up the fender to tire distance a little bit too,when I finally get them installed.

If that doesn't get the ride height where I want it,guess I'll go with the VB&P spring.

[Hib Halverson]

Thanks for the input,Mike & Hib. For starters,I'll probably remove the front shims and install longer bolts in the rear. The new 19" tires are about 3/4" or so taller so that will close up the fender to tire distance a little bit too,when I finally get them installed.
.

No shims, front, two shims on the bottom for the rear and longer rear spring bolts is the set-up I use, but...

Be careful about lowering the car more than that because you'll run out of ride travel. Once the car's on the bump stops, ride sucks and handling goes away.

Also, be careful about using "fender to tire" distance as a measure of ride height. C4s had terrible build quality as far as body mounting and panel tolerances. That is the car to car variance was large. If you're going to accurately measure trim height, do it the way the Service Manual specifies. That's a lot more accurate.

[USAZR1]

Here's what the shims look like when not installed above the spring bushing. my car was slammed and the two aluminum shims are shown here going along for the ride (at least they didn't toss them).

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC03734.jpg~original


How hard is it to remove the two shims? Does it require removing the spring,first?

[mike100]

How hard is it to remove the two shims? Does it require removing the spring,first?

While you do not have to remove the spring or control arm, you still have to remove the lower shock mounts and separate the ball joints to get enough slack on the spring arch to be able to get it to come off of the rubber bushings. This will allow you to unscrew the center mounts and push up the bolts enough to slide shims off the top of the stack.

This of course also requires the removal of the brake caliper since it needs to be hung out of the way because the brake line won't drop far enough when the front end is coming apart.

[batchman]

I believe any of the VB&P springs can be built with C5 style screw-type adjusters, you don't have to go to the "adjustable" spring to vary the height - that's for adjusting the rate. In my case I had to wait a while as they were held up on the parts for this style end but guess they'd be set now.

I'm looking forward to changing mine soon. To that end, anyone have good tip on separating the lower ball joints? I don't want to use a pickle fork on these nice aluminum parts, and that's all I've got handy. A friend uses a pitman arm puller but I don't think the one he has will fit. It seems with 2 C4s I'll need to do this more than once so I don't mind buying a rational tool for the job.

Thanks,
- Jeff

[mike100]

I'm looking forward to changing mine soon. To that end, anyone have good tip on separating the lower ball joints?



This one fits our A-arms pretty well and I have used it several times already without too much drama. Just heed the directions and do NOT use an impact to tighten the jack screw (it will gall).
http://www.summitracing.com/parts/sps-37985?seid=srese1&gclid=CKDE-t3cmr4CFQeVfgodKb8ApQ

[USAZR1]

I believe any of the VB&P springs can be built with C5 style screw-type adjusters, you don't have to go to the "adjustable" spring to vary the height - that's for adjusting the rate. In my case I had to wait a while as they were held up on the parts for this style end but guess they'd be set now.

I'm looking forward to changing mine soon. To that end, anyone have good tip on separating the lower ball joints? I don't want to use a pickle fork on these nice aluminum parts, and that's all I've got handy. A friend uses a pitman arm puller but I don't think the one he has will fit. It seems with 2 C4s I'll need to do this more than once so I don't mind buying a rational tool for the job.

Thanks,
- Jeff


I assumed "adjustable spring" was referring to adjusting the ride height,not the spring rate. How would it adjust the spring rate? I thought the rate was built into the manufacturing process.

All I have access to,is a pickle fork. :confused:

[batchman]

This one fits our A-arms pretty well and I have used it several times already without too much drama.

It's probably just me but I'm having a hard time visualizing this pressing out a lower ball joint. It just doesn't look like it would open wide enough, but again it is probably a lack of imagination on my part!

I assumed "adjustable spring" was referring to adjusting the ride height,not the spring rate. How would it adjust the spring rate? I thought the rate was built into the manufacturing process.

If I understand right (and I'm not certain I do) the two "clamps" in this pic slide in/out and adjust the rate:

http://www.vbandp.com/auto-parts/c4-corvettes.html?page=shop.product_details&flypage=flypage.tpl&product_id=753&category_id=115

Later,
- Jeff

[lbszr]

That style ball joint seperator that was posted above from Summit works really good. I have the one from Harbor Freight http://www.harborfreight.com/front-end-service-tool-set-5pc-60306.html I have lost track of how many times I have had the lower ball joints apart with no problems or damage.

I have the extreme, 1143 spring rate, works good for dialing in the ride height. It is not designed to change spring rate, just ride height. They do have a rear sping with adjustable spring rate, but I do not have it, it would not go high enough for what I wanted. http://www.vbandp.com/auto-parts.html?page=shop.product_details&flypage=flypage.tpl&product_id=553&category_id=115







It's probably just me but I'm having a hard time visualizing this pressing out a lower ball joint. It just doesn't look like it would open wide enough, but again it is probably a lack of imagination on my part!



If I understand right (and I'm not certain I do) the two "clamps" in this pic slide in/out and adjust the rate:

http://www.vbandp.com/auto-parts/c4-corvettes.html?page=shop.product_details&flypage=flypage.tpl&product_id=753&category_id=115

Later,
- Jeff

[mike100]

It's probably just me but I'm having a hard time visualizing this pressing out a lower ball joint. It just doesn't look like it would open wide enough, but again it is probably a lack of imagination on my part!


- Jeff

Technically, you are just breaking the stud taper- Pressing ball joints out is an entirely different tool.

Here is the factory video showing it in use. Granted, the video example is on a small Honda, but the tool just reaches to the top of the stud on a C4. You definitely need to make sure your hands are nowhere near the a-arm as it pops down a few inches fairly abruptly when the stud breaks free.

http://www.youtube.com/watch?v=jOSXVR9MQ7E

[mike100]

Here's a hydraulic variation...never saw one before, but it looks like it requires a much smaller tool turn the screw due to toque multiplication on hyd piston of some sort. anyhow, the way these pop apart in the video is what you can expect on the lower arm of a C4.

http://www.youtube.com/watch?v=OBLyB18Pq4k

[batchman]

but the tool just reaches to the top of the stud on a C4

Thanks, Mike - I think I was not seeing the "fork" shape in the pic, your vid made it clear to me.

They do have a rear sping with adjustable spring rate

Ah HA! It's the rear one I was thinking of. How do you like the 1143, I was looking for more like 1250 but the best they could give me was 1023. I'm fixing to put it on but toying with calling them to see if they've got anything heavier - I figure the LT5 is a fairly heavy lump so more rate than the typical 2x front/rear would make sense, and my rear is about 500.

Cheers,
- Jeff

[lbszr]

Thanks, Mike - I think I was not seeing the "fork" shape in the pic, your vid made it clear to me.



Ah HA! It's the rear one I was thinking of. How do you like the 1143, I was looking for more like 1250 but the best they could give me was 1023. I'm fixing to put it on but toying with calling them to see if they've got anything heavier - I figure the LT5 is a fairly heavy lump so more rate than the typical 2x front/rear would make sense, and my rear is about 500.

Cheers,
- Jeff


Just 2 weekends the springs got their test at the track and it did great. I can comfortably hang in the curves with c6zo6 and some others that have mods, i was getting passed all the time before. There is hardly no body roll. I have pictures that look like a z06 behind me is leaning more than mine in a hard turn. Also what made a huge difference is square set up with 315's all the way around. It feels really balanced now.

Your correct about the ratio, 1200 850 would be better to work with and was recommended to me by somebody that used to race them. 650 was the best I could get for the back, but worked out. 32mm bar front and the biggest they have for the back, 26 I think.

[USAZR1]

A friend of mine offered me the front spring off his 94 w/LT1 that already has the shaved middle rubber and glued wedges. The color code marking is not visible anymore but the number on the spring reads FHA 1-3. Best I can tell,the spring rate is about the same as the one on our 94 ZR-1.
What do you guys think? Will this spring work?

My friend installed Exotic Muscle coilovers on his 94.

[WVZR-1]

A friend of mine offered me the front spring off his 94 w/LT1 that already has the shaved middle rubber and glued wedges. The color code marking is not visible anymore but the number on the spring reads FHA 1-3. Best I can tell,the spring rate is about the same as the one on our 94 ZR-1.
What do you guys think? Will this spring work?

My friend installed Exotic Muscle coilovers on his 94.

'94 spring rates were softened for base FX3 cars to 60Nm, a '94 cataloged service code is HA for '94. Here's GM published front rates for front for '94:

3649

A NON FX3 service code for '94 is JA.

[USAZR1]

'94 spring rates were softened for base FX3 cars to 60Nm, a '94 cataloged service code is HA for '94. Here's GM published front rates for front for '94:

3649

A NON FX3 service code for '94 is JA.


Dropping the spring rate from 75Nm to 60Nm is a 20% drop. Sounds like I better stay with the front spring already on the car.
Thanks,Dave. I appreciate the info.

[WVZR-1]

Dropping the spring rate from 75Nm to 60Nm is a 20% drop. Sounds like I better stay with the front spring already on the car.
Thanks,Dave. I appreciate the info.

I made sure I mentioned the code that's cataloged and also the spring rates from the MVMA direct from GM. So long as your friends LT1 base car was also an FX3 then I'd avoid it I think. A base car '94 with NO FX3 (JA) is very close.

[USAZR1]

I made sure I mentioned the code that's cataloged and also the spring rates from the MVMA direct from GM. So long as your friends LT1 base car was also an FX3 then I'd avoid it I think. A base car '94 with NO FX3 (JA) is very close.


To the best of my knowledge,my friend's 94 did not come equipped with the FX3 option. He told me it was a base car,Dave.

[WVZR-1]

To the best of my knowledge,my friend's 94 did not come equipped with the FX3 option. He told me it was a base car,Dave.

Let's try this then, here's some possibilities. Does the spring just have a flat molded rubber cushion or a "pedestal" type bumper 1 1/4" square and 5/8" tall? If it's a flat molded rubber cushion then it's an earlier FHA from a '91 or earlier. If square "pedestal" type then FSS (coupe no FX3), FSA ('vert no FX3). I overlooked the JA being a 'vert w/FX3 or the HA I already mentioned. Sorry.

It might make sense that your friend bought a spring to modify and have ready to do the change rather than tear apart and then do the work. Maybe he purchased that one modified. The type of insulator on the end is key.

I have 2 FHA springs one of each type, one is removed from a '91 ZR-1 (I'm sure of that) and I have one with the pedestal type that I always thought came from a '93 LT1 car recovered theft with real low miles. I've got control arms and spindles as well for that car. There's no FHA code for '93 cataloged either, mine has NO color code and I don't believe it could have. I can see where there was a label at some time. I forgot that I had the springs to compare because you mentioned '94 so I didn't even consider checking mine.

[USAZR1]

I don't have the spring in hand so I can look it over but I do know that spring was the oem unit for that base 94. He removed the spring,modified it, and re-installed it. About six months ago,he removed it again and installed the coilovers.

If I could use that particular spring,it would save quite a bit of time and I would still have my 94's unmodified spring to keep.

[WVZR-1]

I don't have the spring in hand so I can look it over but I do know that spring was the oem unit for that base 94. He removed the spring,modified it, and re-installed it. About six months ago,he removed it again and installed the coilovers.

If I could use that particular spring,it would save quite a bit of time and I would still have my 94's unmodified spring to keep.

Just do it! Measure the car first and then after install, make sure the car is on the ground when you tighten everything to spec, I'd take it down the road and find some "rumble strips" on the shoulders and median before I tightened to spec. I would think in a few hundred miles of various driving conditions you'll have a very good idea if it was a good call.

[RPO LT5]

Wow, the Z51, Challenge and Z07 cars had some high spring rates and anti-roll bar diameters. And the roll bars were both solid. I'd have to wear a mouth guard and neck brace to drive on DC roads again. I've never seen moon sized crater potholes until DC.