Driveline Vibration
Thread Starter
Racer
Joined: Jan 2008
Posts: 281
Likes: 3
From: Palm Coast FL
Driveline Vibration
94 6 speed, 50k, vibration starts at about 65mph. Not engine related, since I can depress the clutch and the vibration stays. Feels as though it is coming from the rear of the car.
Now then, new tires (Continentals) road force balanced, new rear hubs. All 6 UJoints appear to be in great shape, no obvious slack and no signs of rusty powder. Tried different tire pressures, from 30psi to 35psi.
Just spent the last 1.5 hours reading threads about vibration and the common thread in all of them is that this is a common problem, but 90% of the threads do not end with the original poster explaining how it was fixed.
Have had the car 7 months and it has vibrated slightly since I got it and it is now getting worse. The vibrations are cyclical, in that they come and go in increasing and decreasing amplitude, like a sine wave.
I have thought about shocks, new UJs, rear wheel geometry, but want to see if any of you guys who have had this problem can shed some light?
Cheers (not holding my breathe though
Now then, new tires (Continentals) road force balanced, new rear hubs. All 6 UJoints appear to be in great shape, no obvious slack and no signs of rusty powder. Tried different tire pressures, from 30psi to 35psi.
Just spent the last 1.5 hours reading threads about vibration and the common thread in all of them is that this is a common problem, but 90% of the threads do not end with the original poster explaining how it was fixed.
Have had the car 7 months and it has vibrated slightly since I got it and it is now getting worse. The vibrations are cyclical, in that they come and go in increasing and decreasing amplitude, like a sine wave.
I have thought about shocks, new UJs, rear wheel geometry, but want to see if any of you guys who have had this problem can shed some light?
Cheers (not holding my breathe though
Melting Slicks
Joined: Jul 2006
Posts: 2,151
Likes: 0
From: Strongsville Ohio
over the years and a couple cars I have come accross a bent rim, out of round tires, U-joint bearing pin bent inside the cap, the weight off my driveshaft on the C4 missing..I would check things that need to be there like the weight off the driveshaft, tie rods, bearing tightness...
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 276
From: Melbourne, Victoria, Australia
Check your tires, if they are slightly out of round you will get vibration.
I have had brand new tires do this, there was a problem with the manufacturing and i got another 4 new ones.
Best bring the vette to a tire shop and get the wheels balanced, it is easy to loose the adhesive weights. They will tell you if there is a problem with the tires.
Also check if the vibration is worse with higher pressures, that will show up out of round tire problems.
I have had brand new tires do this, there was a problem with the manufacturing and i got another 4 new ones.
Best bring the vette to a tire shop and get the wheels balanced, it is easy to loose the adhesive weights. They will tell you if there is a problem with the tires.
Also check if the vibration is worse with higher pressures, that will show up out of round tire problems.
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
If your problem is wheel- or tire related, you might get a clue as to the cause by swapping tires left to right to see if the vibration changes. Your car has staggered tire and wheel sizes front to rear, not sure if a front-to-rear swap will fit, but if it will, try this also. You would want to do only one change at a time, then drive the car to see if you can detect a difference. If there is a noticeable change, you can then infer that the wheels and/or tires involved are the cause. You would be looking for a bent rim, or something that would not have been affected by the replacement of the tires. Also, it is not unheard of for a vibration to originate at the opposite end of the car from where it seems to be.
Pro
Joined: Oct 2003
Posts: 506
Likes: 12
From: Savannah GA
From the checks you've done pull a halfshaft out and look at an outer u-joint. They will cause the shake you discribe. Get good u-joints, they aren't much more in price.
The job can be done at home. They're plenty of posts with pictures.
I've done it twice on my 87. The last time I didn't see any dust either.
The outer one will show the wear first.
Js
The job can be done at home. They're plenty of posts with pictures.
I've done it twice on my 87. The last time I didn't see any dust either.
The outer one will show the wear first.
Js
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Thread Starter
Racer
Joined: Jan 2008
Posts: 281
Likes: 3
From: Palm Coast FL
Yep, at approx 65mph it starts to rumble, and increases all the way to, as to date, 115mph. At 60 it is like silk. If it was a wheel/tire problem I would have thought it would have made itself noticed before 65.
I will go and get the wheels double checked. When I replaced the rear hubs it reduced the vibration somewhat, but it is still there. I did check the UJs and they felt rock solid, no play at all.
I will look and see if the drive shaft balance weight is still there. Not sure if any of the POs ever pulled the shaft. Everything looks original down there, but who knows??
Here's a dumb question...where do I take the car to have the drive-shaft balanced? Will my local Chevy dealer be up to it, or is it more a specialist job?
I will go and get the wheels double checked. When I replaced the rear hubs it reduced the vibration somewhat, but it is still there. I did check the UJs and they felt rock solid, no play at all.
I will look and see if the drive shaft balance weight is still there. Not sure if any of the POs ever pulled the shaft. Everything looks original down there, but who knows??
Here's a dumb question...where do I take the car to have the drive-shaft balanced? Will my local Chevy dealer be up to it, or is it more a specialist job?
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
Yep, at approx 65mph it starts to rumble, and increases all the way to, as to date, 115mph. At 60 it is like silk. If it was a wheel/tire problem I would have thought it would have made itself noticed before 65.
I will go and get the wheels double checked. When I replaced the rear hubs it reduced the vibration somewhat, but it is still there. I did check the UJs and they felt rock solid, no play at all.
I will look and see if the drive shaft balance weight is still there. Not sure if any of the POs ever pulled the shaft. Everything looks original down there, but who knows??
Here's a dumb question...where do I take the car to have the drive-shaft balanced? Will my local Chevy dealer be up to it, or is it more a specialist job?
I will go and get the wheels double checked. When I replaced the rear hubs it reduced the vibration somewhat, but it is still there. I did check the UJs and they felt rock solid, no play at all.
I will look and see if the drive shaft balance weight is still there. Not sure if any of the POs ever pulled the shaft. Everything looks original down there, but who knows??
Here's a dumb question...where do I take the car to have the drive-shaft balanced? Will my local Chevy dealer be up to it, or is it more a specialist job?
Le Mans Master
Joined: May 2005
Posts: 7,354
Likes: 2,278
From: Central Maryland
I would NOT go to the dealer- they will just take the shaft to a shop that specializes in driveline work, and charge you a chunk of cash for their efforts. You should be able to find a shop like that yourself, all you have to do is bring them the shaft. If you are unable to remove it yourself, then you will need to take the car to a repair shop (ask around for a reliable one). I would still not take the car to the dealer.
I had very similar symptoms in my '94 six-speed car, and the cure turned out to be a replacement front yoke on the driveshaft, and a new tailshaft bushing (and seal, too, of course).
I don't recall the exact numbers for acceptable lash between the yoke and tailshaft bushing, but Bill Boudreau at ZF Doc can tell you. If yours exceeds this limit, there's an excellent chance that addressing this will solve your problem.
Good luck. Let us know how it turns out.
Live well,
SJW
Pro
Joined: Aug 2009
Posts: 725
Likes: 4
From: Plano, TX
I recently had mine balanced at Cincinnati Driveline. They also replaced my ujoints with the spicer units. I just removed the driveshaft myself and carried it in.
My driveshaft was very badly out of balance due to an auto to ZF6 swap so I noticed a huge improvement in high speed stability. I've had it up to 120mph and it feels like silk. Remember the driveshaft turns 3-4 times as fast as the half shafts so even a little imbalance is annoying.
My driveshaft was very badly out of balance due to an auto to ZF6 swap so I noticed a huge improvement in high speed stability. I've had it up to 120mph and it feels like silk. Remember the driveshaft turns 3-4 times as fast as the half shafts so even a little imbalance is annoying.
Last edited by 93VettePilot; Nov 8, 2011 at 12:30 AM.
Thread Starter
Racer
Joined: Jan 2008
Posts: 281
Likes: 3
From: Palm Coast FL
Well, I hate to admit it, but it was tire balance. I bought the new Continentals, and the guys told me they had road force balanced the wheels. Yesterday I took the car back in to absolutely rule out tire imbalance. It looks like the first balance was bad, cos each wheel was at least 1oz out, and one rear tire needed to be rotated 180 degrees on the wheel. Big improvement at 65+mph.
Just wanted to bring this thread to a logical end
Just wanted to bring this thread to a logical end
