I have an A6 Q auto with a weird thumping while accelerating. It sounds like the driveshaft thumping against the bottom of the car, but I can't find any play. It seems to it it under torque. gears 1,2 or 3 it will do it if I give it some gas. I have 220,000 miles on the car and I have brand new tires and just had control arms/tie rods and an alignment done as well. It has been doing this for a year and it is progressively getting worse. I brought it to a shop and they couldn't find anything. I may have to bring it to the dealer. Anyone have any ideas? BTW, it is an A6 2.8Q. Sorry about the title

 

Open trunk to release GF--

 

Sounds like it may be the CV joints on the driveshaft (the one between the front/rear diff). I just got this fixed in my car six days ago: bought a used driveshaft on ebay (part #4B0 521 106 C if you're an automatic) for under a hundred (low-ball the make an offer option) and then had it installed for $180 at a local shop. Done and done.

This is only a guess, but for more information regarding troubleshooting check out Blau's site on this condition: http://www.blauparts.com/audi/audi_d...pair_kit.shtml

Other options include going to a dealer where a USED shaft runs $741, you could replace the CV joints on the driveshaft ($100/side and you might still need to buy a new center support), or just hope you're lucky enough where taking the CV joint apart and repacking it does the job (ha). I would recommend getting a used one with preferably low miles. The 4B0521106C was used in the every A6 with automatic V6 engines from 1998 through the 2004 models (based on part numbers from my servicing program).

 

Thanks for the tips.....I was wondering what happened to my GF! My wife must have figured it out. I think the issue is the driveshaft, prolly the rear cv joint or center bearing.