Yes, I did change the transmission fluid, I have an automatic. is yours an auto or a manual? If its an automatic i have some info for you so you can do it yourself.

i also changed my rear diff, center diff ( which i rebuilt also ), and front diff ( which you won't have if yours is a manual transmission).

 

It's an automatic. Thanks for the info.

 

I had this issue when I replaced my plugs and wires. It was a bad wire (which was brand new) causing one of the cylindars to misfire. It was throwing a code for me though. Is your check engine light coming on/blinking when you accelerate?

 

This happened to me just after I got my car. Instense vibrations, only when accelerating, not when coasting. I know I had a bent since I had to drive on a flat to get it replaced. The issue was fixed but with three different solution, first thing done was a wheel alignment and balancing at the dealer this was when it first happened, that got it almost fixed. It would still occur on a certain stretch of road on my way home from work (its probably a combination of a cold engine doing 60 on a curved hill that still causes it.) The second thing done was a coolant flush (did it earlier this month) becuase my coolant was brown looking. That helped to smooth out the engine a bit. And the last thing done that has almost eliminated the vibration was a steering pump replacement (and subsequent engine wash). All of this work was done at the Audi dealer. As I said the problem is nearly gone now, so your issue, pec2402 is probably a combination of things like it was with mine.

My car is a 2003 3.0 with tiptronic.

Another thing to note on my car that may be useful information, is that I'm running on the stock 18's with one tire not matching the other 3 (the one that went flat). The car was purchased with one of the tires not matching (again the flat one) and the spare also did not match the others. I am now running on my spare, with the new tire and the previously bent, but now hammered out wheel in the trunk.