Possible sources of vibration?

[Larry T.]

I have a vibration that occurs most noticeably under heavy acceleration. It is also noticeable in the steering wheel at cruising speed over 45 mph or so, although under acceleration it feels like it could be "shimmying" under the car or at the rear. For reference, with 4.11 gears I run about 3000 rpm at 60 mph. Runout should not be an issue as it is between .003" and .004". Wheels balancing was just done.

My thoughts are half shafts, drive axle or flywheel/clutch/pressure plate. I also have aluminum knock offs. Could a wheel be damaged that causes vibration when driving but still balances out on a machine?

Thanks for all input.

[Wayne W.]

Re: Possible sources of vibration?

A worn, sagging, rear with lots of negative camber will cause vibration under load.

[Daniel S.]

Re: Possible sources of vibration?

Poor wheel alignment (front and rear), check the control arm bushings, maybe a bent wheel...

[Duke W.]

Re: Possible sources of vibration?

The fact that it's load sensitive makes a worn U-joint a prime suspect. It could also indicate deteriorated drivetrain mounts - engine, transmission, or axle.

Vibration from wheel/tire unbalance/out-of-round is usually not load sensitive - just speed senstive.

Duke

[Dan P.]

Re: Possible sources of vibration?

If the vibration is under a load sounds like you have something touching metal to metal when the motor torques. The motor is mounted in rubber and if any part including the exhaust touches metal to metal it will cause a vibration. The next thing to do is put the car on jack stands . With the stands under the rear axle so the rear suspension is loaded like the car setting on the ground . Run the car up to the speed that it vibrates at . If there is no vibration probably in the front end.If you feal the vibration take the wheels off.Put the lug nuts on backwards to hold the drums on and run the car. If it still vibrates take the drums off. if it still vibrates look at the driveshaft or ujoints.

[Tracy C.]

Re: Possible sources of vibration?

Someone recently posted that had a similar issue and found the front bearing in his muncie to be the culprit.

Find yourself a long relatively steep downgrade, pop the car in neutral and let the motor idle as you coast down the hill at speed. This will help you determine if the vibration is in the driveline or your wheels and tires.

tc

[Timothy B.]

Re: Possible sources of vibration?

Larry,

The problem could be a front wheel bearing. A test that may give some indication is to turn the steering wheel left/right while driving and see if by unloading the bearing the vibration goes away.

[Michael F.]

Re: Possible sources of vibration?

If the vibration is under a load sounds like you have something touching metal to metal when the motor torques. The motor is mounted in rubber and if any part including the exhaust touches metal to metal it will cause a vibration. The next thing to do is put the car on jack stands . With the stands under the rear axle so the rear suspension is loaded like the car setting on the ground . Run the car up to the speed that it vibrates at . If there is no vibration probably in the front end.If you feal the vibration take the wheels off.Put the lug nuts on backwards to hold the drums on and run the car. If it still vibrates take the drums off. if it still vibrates look at the driveshaft or ujoints.

Can't safely load the axle on a C2 with jack stands. I would love to be a fly on the wall when that baby slips off the jack stands at 60 mph on the speedo.