Alfa_Metal

Hello,
First post. Apologies if this is redundant but I couldnt find the same problem in a search. The car is a manual transmission. When I pull away in first, there is a single knock sound coming from the rear of the car. It occurs at about 5-10 mph. A couple times it's happened in second, if I shift at a low speed. The noise does not occur when slowing down. I can't take the car in for 2 weeks so I'd like to know if i should stop driving it. Could this be the differential? Or differential mounts? There's nothing in my trunk btw. Thanks in advance.

SloopJohnB@mac.com

Unusual but not unheard of. If you can get under the car or jack/jackstands, you might be able to twist the driveshaft back and forth and see how much play you have. There should be zero play in the driveshaft(s) (two piece)--hold the front or rear and twist the other, it's a little more tricky checking the front and rear U-joints but you should be able to feel a loose joint. You might also be able to see a torn differential mount bushing as well. Rear suspension arms/bushings can be checked as well as rear shock mount(s). OEM rear shock mounts are pretty durable, 100K or more. I only had rear shock mount failures on a 2000 4.2A6Q after 107K miles when I went to Koni sports.

Alfa_Metal

Thank you for your input! If its the u-joints, does the whole drive shaft need to be replaced?

SloopJohnB@mac.com

It appears Audi balances the shaft assembly. I've had several Audis however and not had to replace the driveshaft so it would be unusual. Certainly warranty if still covered.