slattts

.. and subtle but got worse pretty rapidly and was soon accompanied by grinding noises from the joints and was evident at all speeds. Dealer's advice was 'we could tear your tranny apart, but you might as well wait until it gets worse and it'll be easier to diagnose'! The indy guy diagnosed it on a 3-minute test drive, correctly as it turned out. He did say he had never seen a quattro drive shaft go bad but does beemers all the time.

These drive shafts do have a central support bearing, and I believe it's capable of adjustment fore and aft for balancing purposes at installation. So presumably it could go out of adjustment or just wear out...

duodallas

I had the suspension checked and wheels aligned, no problems there, but the whole car shook at 65 MPH, even after a half dozen balance jobs.

I did some searching on the web and saw TSB's from Toyota and Mazda for a similar problem, where bolt-centered wheels are balanced on a hub-centered machine (Hunter). The last time I got my tires balanced I noticed an eccentricity of the wheel edge when rotating (1/16"). Sure, you can get the wheels perfectly balanced, but if the wheel is not centered on the Hunter it will NEVER be balanced on your car.

I bought 2.7TDallas' BBS RC's with old Michelins and put them on my car without balancing them first. NO vibration! Why?

The BBS RC's were much lighter than my old wheels (MM Spyders), which changed the resonant frequency to something higher than 65 MPH. I've gone 100MPH and haven't felt vibration yet. More proof, the MM Spyders didn't vibrate at all with my non-sport springs. Only with the coilovers did I have a problem. Resonance frequency, again, the square root of spring constant divided by mass.

And most importantly, the BBS wheels didn't have a hub spacer and were perfectly round.

The wrong tire/wheel weight can make the problem worse.

s4master1

i check the transmission mounts they create vibrations at times specially at higher speeds and hard acceleration
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