BuzzinHornets

Had my 95 on the dyno yesterday and they noticed a vibration in the driveline from about 45 mph up to 90. I have noticed a vibe in the car on the highway between 65 and 75. Taking it back in on Monday but in the meantime thought I would pick some brains around here. Car does have carbon fiber half shafts and the wheels all balance out fine. Any ideas of what could be the issue?

ninetyfivevette

I've got the same problem with my 95 as well.. Wish I could help. I think it might be driveshaft related.

PDQUIK95

Definitely sounds like driveshaft related assuming the carbon fiber half shaft are top quality pieces as they should be.Is it an auto and, if so, is the damper collar still on the forward shaft yoke? That could be an issue or maybe u-joints. Cant answer for a stick shift shaft.

Rick Geer

VetteMed

Try unbolting driveshaft and turn 180 degrees.

BuzzinHornets

Interesting you mention that, at the shop they did mention that the drive shaft or half shafts could be "out of phase". I understand what that means but don't understand how that would relate to drive shafts. Can you elaborate on that issue maybe? How would that cause the vibes?

WW7

This has worked on a number of cars for me in the past..WW

BuzzinHornets

Sorry I left that out, it's a 6 speed, 51000 mi.

littlesk8cracker

same thing on my 94 6 speed, its not bd, but noticable between say 65 and 75. iv changed u joints on the driveshaft but no help. im gonna try half shaft u joints. also wondering if it could be caused by my really old tires

ninetyfivevette

I believe the FSM details a method for balancing the driveshaft using hose clamps. Use two, starting 180 degrees, then adjust until the vibration goes away. I don't recall exactly where you're supposed to put them, but there are plenty of mentions of this method on the internet. If that solves the problem, might consider shelling out the cash to a driveline shop to have it balanced permanently.

drmrman

This is strange. I compeletly forgot about this.

I had the same high frequency low tone humming/vibation at highway speeds aswell. Until I replaced my trans. I dont remember ever having this issue since?... 93 ZF6 50,000 miles.

gkrynick22

VetteMed is probably right. Driveshafts are balanced and if you don't put them in exactly how you took them out you will have a vibration like you guys are describing.

Paul Workman

Couple things to try:

When the vibration is present, shove in the clutch and let the engine rpm drop to idle. If the vibration does not quit - that eliminates any clutch/FW related issues...

If there is any "wiggle" in the U-joints, they need to be replaced. I recommend Spicers, that DO NOT have the grease nipple.

Related to what VetMed said, try first uncoupling the drive shaft from the differential and rotating the shaft 180 degrees. Note: A good thing to do is paint a mark on the driveshaft and the yoke before removing the driveshaft for any reason. This will assure you get it back on in the correct location. (made a world of difference on a couple of my cars).

Also, pry up and down on the drive shaft yoke on the transmission end of the shaft. Then from side to side. If there is play you can feel (rule of thumb), then the tail shaft bushing & possibly the yoke are needing to be replaced for sure. (No big deal, but the C-beam is going to have to be moved out of the way.)

I doubt the half shafts would give you any vibration; rotational velocity is relatively low. A humming or buzz type of (higher frequency) vibration is drive line related. But, I suppose anything is possible.

The driveshafts are a bit more complicated than some might realize. Ideally the tubing wall thickness should be uniform, and the two yoke ends welded in place so that runout is within tight tolerances. Then the mating yoke halves come into question as well. For this reason it is sometimes necessary to balance the drive shaft while connected to the car. (As mentioned, the FSM covers this and the procedure to null out the resulting vibration.)

If you can't get it fixed to your satisfaction, a drive line shop can fix you up pretty quick. BTDT.

P.

Frizlefrak

I know you mentioned it's not an auto, and I'm not schooled on the 6 speed, but on my last Vette it had a vibration much like you describe that I never could track down. I eventually had the transmission rebuilt for other reasons, and the vibration went away. I asked my trans builder, and he gave the exact description Pete just did. If you can't locate it anywhere else, the transmission may be the next thing suspect.

As a point of reference, I always mark a drive shaft, half shaft etc before removing and index it the same way going back in.

earthquake68

Mine had the same vibration. It turned out to be the outer half shaft u-joint on the driver's side. I replaced all four just be thorough. I found two more bad u-joints while I had it apart.

BuzzinHornets

Did you notice any noise associated with the u-joint at very low speed? I did not notice until they guys at the shop said something but there is a slight clunking sound at low speed.

earthquake68

It should've had a clunking noise with all the play that was in there, but honestly I didn't notice until I checked them. The outer u-joint was almost completely worn in two.