here is one for ya

[vailshred]

B6 S4 sedan. Car is vibrating while accelerating at any speed BUT only when the car is warm or hot. Let the car sit for a few hours... No shaking at all. Its a manual. Just did a huge road trip with no vibrations at all. When I got home I pulled the front clip off to fix a aux radiator leak and I switched out the radiator support with one off a parts car I have since the one that was on the car was pretty beat. I also put some different rims and tires on the car. They were balanced prior to install.

Vibrating goes away when in a deep left turn... It actually is smooth as shit when in the turn but as soon as I return to driving straight it returns. If I let off the gas or rev the motor in neutral there is no vibration.

I was going to start with the wheels but I am completely stumped with the vibrating going away when the car is cold.

Any insight, experience or suggestions would be appreciated

Thanks in advance

[FastEddie]

Try fixing your Snub mount. If you havent replaced it yet i would get the 034 snub mount with bracket. Pretty cheap. Ive read your snub can give nasty vibrations is not in right and if you had no vibrations before pulling the nose and now you do i would start there.

You said the wheels (not rims) were balanced so i dont think thats the issue although they could have been balanced improperly. However, unbalanced wheels typically only occur at a certain speed say 50 to 60 and will vibrate only during said speed, doesnt USUALLY matter if you accelerating or decelerating.

Could be a transmission mount as well. You said its only happening when your accelerating and when you revs or let off gas that it goes away.

One more thing to look at is the Axles.

[Hooblah]

I have almost exactly the same problem. All my mounts are good. Possibly dual mass flywheel?

[vailshred]

I ran the symptoms by a few friends. Axles or driveshaft.
The axles had very little play in them so before I pulled them out I dropped the cat back and looked at the driveshaft and could see that is was not straight. It went from tranny to carrier on a slight andle towards drivers side of car then from carrier bearing to rear diff it was angled cack to center, I loosened the carrier bearing and moved it back to straight and It completely helped a ton. Although there is still a very small rattle it is not even close to how bad it was prior to straitening the driveshaft.
Its pretty amazing how hot the driveline gets when the car is hot. My axles and driveshaft were nearly to hot to touch after a 2 hour spin.

[vailshred]

check the inner cv joints and the driveshaft. I also read that a locked up brake caliper can cause this issue or even the steering rack. I would start at inspecting the axles and driveshaft

good luck

[neilpaku]

Might want to check the bearings in that driveshaft, the bushing in the rear of the transmission, and the pinion bearing and seal in the diff. If the driveshaft has been flogging around, it has accelerated wear in those components.

[FastEddie]

I still think you snub isnt aligned right.