I recently became the proud owner of a 1996 Audi A6 Quatro. I've had the car for about six months and love it until recently. I have noticed when I slow down to speeds of 5-10mph there is a thumping noise or rumbling coming from rear end. I can come to a stop and then when I start moving again the rumbling will occur until I get up to about 20mph-then it quits. I am wondering if I have a bad bearing, a bad differential seal, or a bad differential altogether. Please send help! Brian

 

I would get under the car and check all the bushings and check for leaks. Then check for play in the diff. Pretty hard to diagnose by the description you gave. Good luck.