Update on my hi-miler Z project

[VetteMed]

Originally Posted by Dynomite

Was that Nitto 555 Extreme Performance or Nitto 555R Drag Radial on the rear. I assume Nitto 555 Extreme Performance on all four

And you would ASSume correctly 555EP all around.

[GOLDCYLON]

Originally Posted by VetteMed

Car sat for maybe 6 weeks or so, but most of that time was on jackstands, no load on tires. Banski stuff was installed over a year ago, and I recently had a four-wheel alignment which got the car pretty close to what I'd consider correct. I brought it back to the shop once, and they tweaked it and got it closer, but I kind of gave up on perfection at that point, as other issues were needing attention.

I had Nitto 555s installed a few months ago, and they did a standard balance, not road-force. I honestly can't remember if the problem got worse after the Nittos were installed. My brain is starting to go....

hmm rotate that drive shaft yet ?

[VetteMed]

Originally Posted by GOLDCYLON

hmm rotate that drive shaft yet ?

Planning on it, as mentioned above! Probably oughta try that before spending money on road-force balancing

[GOLDCYLON]

Originally Posted by VetteMed

Planning on it, as mentioned above! Probably oughta try that before spending money on road-force balancing

I would just to rule it out

[VetteMed]

Rotated the driveshaft 180 degrees today, I'd say that helped by maybe 20%. I took the car back to Discount Tire, where the Nittos were mounted a few months ago, and they re-balanced all 4 tires. I'd say that helped by at least another 50% or so. The manager didn't think road force balancing was going to be worth the cost, but I may go back and have them do that at a later date if I'm still not satisfied with the level of smoothness.

[GOLDCYLON]

Originally Posted by VetteMed

Rotated the driveshaft 180 degrees today, I'd say that helped by maybe 20%. I took the car back to Discount Tire, where the Nittos were mounted a few months ago, and they re-balanced all 4 tires. I'd say that helped by at least another 50% or so. The manager didn't think road force balancing was going to be worth the cost, but I may go back and have them do that at a later date if I'm still not satisfied with the level of smoothness.

OK hey 70% better is an improvement Im thinking 4 wheel alignment again will get that next 30%

[limey]

I must say Andrew, you are one motivated owner! 70% improvement is probably as good as you're going to get.

Make sure you drain and change the oil after about 500 miles or so and report back how things are going, be interested to see for my own benefit if not the least the other guys, how well the car and rebuild does as time and miles progress.

[VetteMed]

Kurt, you're probably right about not being able to get 100%... though earlier today, I did manage to tighten the hood latch bumpers to take out some of the slack, which was leading to rattling that accentuated the vibration I was feeling.

I'm at about 400 miles on the motor now, so I'll probably change the oil over the weekend.

Updates will still occur regularly

[VetteMed]

I hit the 500 mile mark today, so I changed the oil. The magnetic drain plug had about a 1mm thick layer of fine particulate adhered to the tip. The drain pan had some very very fine sparkly metallic material present, visible but not able to be detected by touch. I am assuming that is fairly normal and is associated with break-in.

I also am going to amend my prior finding of 70% of the vibration issue being resolved. It's more like 90% now that I adjusted the hood properly. It only was 1/4 turn of the passenger side hood bumper, but it was enough to take the slack out of the latch assembly. Previously, the hood was visibly vibrating, and audibly rattling, giving the impression that the car was much shakier overall. I'm quite happy with the level of smoothness now that the hood is stable.

[VetteMed]

Originally Posted by Dynomite

Hi:
You rotated the drive shaft .......20% of issue went away.
You balanced tires.....50% issue went away (total 70%).
You thought about it.......another 20% of the issue went away

I do not understand how the drive shaft balance (20% of problem) and tire balance (50% of problem) would not be rpm dependent (in gear at 75 mph or lower speeds in same gear).

I do not understand how depressing the clutch while at 75 mph would reduce the vibration if in fact you depressed the clutch at 75mph and let the engine idle as you were coasting at 75 mph.

I assume (the sp just for you ) the circumstances are not as I envisioned from your explanation

Depressing the clutch while at 75mph, would reduce a driveshaft vibration, because it's unloading the driveshaft from the transmission end. Yes, it's still spinning, but it's unloaded, basically.

Depressing the clutch would have no impact on vibration due to poor wheel balance, because the forces that induce vibration in the wheels would not be changed, as I understand it. I'm no physicist or engineer, though.