Hey all first real post here.

I have a 1996 Camaro RS with the 3.8 V6, 5-speed manual, and limited slip rear end. Transmission has been gone thru and is said to be good, driveshaft is new and balanced (by two different shops), my tires and brand new and just balanced. New fluid in transmission and differential.

At highway speeds (>60 mph), I get this persistent rumble and vibration coming through the car, its very low pitched, reminds me of an imbalanced driveshaft but the two shops I use insist the driveshaft is fine. I also had my driveline angles checked, they were fine. What else could cause this? Wheel bearings? differential bearings? The car has been wrecked in the right rear, so I'm wondering if it caused some mechanical damage as well.

Any help is appreciated. I bought this car for $1300 thinking I got a good deal...now, I have over $7500 into it and I still have problems. Thanks!

 

could be the engine mounts or tranny mounts

 

I wasthinking wheel bearings, even before getting to the part about it getting wrecked in the rear. Do you know what kind of impact it was? If the wheel was hit, it could have done some damage to the bearing, or tweaked the axle (which caneventually end up ruining the wheel bearing).

 

Forgot to mention that the engine and transmission mounts were just replaced.

I don't know exactly what kind of impact (it was done before I bought the car) but the rear-right quarter panel has obviously been replaced. Also, I haven't seen this for myself, but one of the mechanics said the torque arm mount at the transmission had been kind of jerry-rigged.

I would love it to just be a wheel bearing! Whats the best way to test this? I was concerned that it might be inside my differential (could a worn limited slip mechanism cause this?) but obviously would rather not gut my diff if I don't have to.

 

Bump, anyone?

 

So I installed two new axle bearings today. Problem still remains. The old bearings didn't show any signs of obvious wear.

 

This type of problem is the hardest to do over the internet. For us to help we would need more details Like:
Does the vibration get less or more with light load or hvy load?
If you bank the car left or right does it change the vibration level?
Do you feel the vidration in the seat of you pants, steering wheel, brake petal or theshifter?
It can also be helpful to get someone to drive the car while you crawl around looking to see where the noise if coming from. I have riden in trunks and removed hoods and hung over motors whilesomeone else drove looking for vibration.

Back in the day we had a tool called a reed tach. It would measure the Hz of a vibration. You could then do the math and see what was turning that speed. It could not tell what was wrong but it could tell if it was in the drive line or the rear.

IMO, Common issues to look for in order, most common issues first:
Drive shaft to transmission slip joint clearance (tranny output bushing)
Bent axle.
U-Joint
Wheel bearing
Pinion Bearing
Carrierbearing
Drive shaft Balancing
Drive shaft phasing
Damaged carrier (causing out of balance)
Axle tube bent.

This assumes a hard to find issue. Most older cars that come in with vibration issue just have worn out bushings or the exhaust laying on the axle or something like that.

Edit:I added U-joint to the list, I believe I forgot U-joint

 

You mentioned it has a new motor and tranny and it is a manual, It could be a misalinged throwout bearing or somthing in the clutch assy, does it change or go away when you put the clutch in and coastat the speed it hapensat???

Also it could be as simple as a bad tire, bad tires do all kinds of weird stuff. Bent axles are hard to diagnose as they can look perfectly straight by eye or by spinning it by hand.

Good luck

G

 

I would suspect a bent axel if it has been hit in the rear right around the wheel. But
i would think you would be able to feel the *** end wabble while driving.

 

Thanks for the replies.

The noise is present all of the time above 60 mph, worse at 65 mph, hard to tell if it levels of above 70 because road noise gets much louder. Seems to get louder on deceleration. I don't think steering makes any difference. I mostly HEAR the rumble, not as much feel it, but it does seem like its coming from the tail end of the car, not the front end. When I had the car up on jackstands in the rear,at 65 mph the noise was still there. It was actually much louder when it was on the stands.

The rumble I hear is almost certainly around 50 Hz, based on using a microphone and FFT software...And from my calculation, that's how fast the driveshaft is spinning at 65 mph, although it bothers me that the driveshaft has been cleared by so many mechanics.

Noise does NOT go away when car is in neutral, or when clutch is in. The car doesn't have a new motor and trans, but new motor and trans mounts. Trans was inspected by a local shop and said to be good.

How could I check for a bent axle? The car doesn't wobble.

Thanks all!