Gerry

The car is an '02 S6 with 94k miles. I am experiencing a bit of a rumbling vibration at very low speed with relatively tight steering angles. Its not always consistent, but backing out of my driveway and turning around will do it and I sometimes do notice it when pulling away from being parked. It occurs in either forward or reverse. Engine loading seems to vary it as well. My independent Audi mechanic says hes sure that it is not CV joints or driveshaft bearing and although he's not sure, is leaning towards the transfer case / torsen diff area. He says even though he's worked on many hundreds of Audis over the years he's not had much work to do on the Torsen diffs so he doesn't really know their problems. We've checked and changed the gear oil in all three boxes and there weren't any surprises. I'm wondering what thoughts you all might have regarding transfer case or torsen issues? Also, I am the original owner, so I know there is no history or previous work in those areas.

Metronet

Was the rumbling vibration felt at steering wheel or seat? Any clunking noise?

Long shot but are the steering rack bots tight? they should be tighten to 67 Nm I believe.

https://www.audiworld.com/forums/a6-...oblem-1715833/

Good luck!

Gerry

The feeling seems to be mostly seat but some steering as well. I think I'm going to need to put it up on jack stands this weekend and just go over everything. It is definitely related to torque though, as it occurs with slight gas pedal and stops when lifted, without any release of steering angle.

N_Jay

I noticed a little of that and it got better when topping up the center diff (it was very low).
If your fluids are good, maybe something else is causing it to bind.

SloopJohnB@mac.com

There should be ZERO play when you hold the axle and move the wheel CCW and CW. If there is, replace the rzeppa joint or axle assembly.

When you turn the axle, there should be zero rotational play between the axle and the transmission flange..this is a little harder to ascertain because it's difficult to lock the transmission output flange.

There may well be rotational play when you simply lock the transmission in park and move the wheel ccw and cw. But this is generally transmission/gear slop. If you have, say, 90-180 degrees of slop, then you may well have a transmission or combined axle/transmission problem.

Classic rzeppa joint problem is clicking when at full lock and moving slowly…try it in a parking garage when it's quiet and you can listen. The outer side is generally at a higher angle than the inner side but at low speeds isn't loaded much more than the inner one.

With the car up on jackstands you can also run all four wheels in drive and actually listen to the wheel bearings at each station…they should all sound the same. Any one of them louder than the others is a bad wheel bearing. It's extremely unusual to have all four corners bad bearings.