ajg617

Admittedly getting a little frustrating. 2nd prop shaft put in and now still getting the same or worse whole car vibration. It is worse now than it was two weeks ago and I can feel it at all speeds above 30. This all started after I replaced the prop shaft as my center bearing rubber was shot and the shaft was hitting the exhaust system every time I accelerated.

Put a used shaft in and immediately felt the vibration and heard a ticking sound the frequency of which varied with speed of the car. Thought the used shaft was bad and put a rebuilt in. Same thing. In the meantime I replaced the RF axle as the boot was torn and it had over 100k on it.

So I ran across a post about front engine mounts and how if bad, they can ruin the front axles. Now I'm thinking that is the problem as mounts are leaking or have leaked in the past. I was told that all mounts needed to be replaced some time ago maybe a year but that I need to start with the rear mounts. Both rear mounts on the trans were so bad that they had a good 3/4 inch of play the rubber was so worn. But I was never sure (actually still not sure) how to tell if there is any hydraulic fluid left in the fronts and just how bad the front mounts might be.

Can front mounts cause prop shaft vibration due to change in angle of the engine/trans or am I likely feeling the vibration from the front axles? I don't feel anything in the steering wheel - it's the whole car. In fact you can hear a hum from just under the shift lever (that's about as close as I can tell as a source point and it definitely changes with speed of the car). I only have a hundred miles on the prop shaft (rebuilt) and RF drive shaft which was new but not Audi. It's almost not drivable due to the vibration.

Front mounts next. I'll probably replace the LF axle as well since it has well over 100k it it is not an Audi axle. Not sure what else to do if that doesn't take care of the vibration.

TIA,
AJG

dwengi

There is a fixture that keeps prop shafts aligned during installation - then you shim and tighten the center support bearing mounting bolts. Did you use the fixture or just bolt it in? In my experience even slight misalignment of the shafts causes serious vibration.

ajg617

My indy did the prop shaft on the second go around. He has all the Audi equipment (actually trains the local Audi dealer techs) and is tops with VW/Audi. Pulled the shaft for torque converter and it ran great on same car 60K back. I just am having a hard time with thinking two replacement shafts are bad or not installed correctly but it started with the replacement of the first shaft.

Huskerbob

My money is on a misaligned prop shaft. First guy lost the shims and second guy didn't replace them. Easy to do. It's gotta be straight and the center support is the key.

ajg617

Think you are correct. Have it being re-installed correctly at Audi.

Huskerbob

Good luck. You'll like it better without that vibration.

ajg617

Had it done today - what a difference. Should have done that in the first place. .

Huskerbob

Ain't it nice?

dwengi nailed it with his post.

ajg617

Yes he did. The frustrating part is the indy that does put the second one in has the jig but....Guess he was rushed - he's gotten more work than he handle lately.

Huskerbob

Well if he keeps taking shortcuts he'll soon have less.