Diff noise?? from the 04 RS6
 

Just replaced all tires on the beast (again:D), and had the tech check out the car. Have had a whining noise for a while and put it down to rear tire wear, they were really cooked. After putting on the new tires the noise is still there. Checked the rear wheel bearings and they are OK. I'm now thinking rear diff problems. Definitely from the back end. Increases with speed. Sounds like bearings, not the R&P. Any ideas???

Re: Diff noise?? from the 04 RS6
 

Problems in the driveline are, in my opinion, the most difficult thing to diagnose on a modern vehicle - you've got the clutch assembly, transmission, axles, differentials, angle drives, driveshafts, bearings, brakes, wheels, tires, etc. How many KM on the car? Have you changed the diff fluid? No matter what Audi says, no vigorously-driven performance car should go 7 years without new diff/tranny fluid. If you've got no vibrations, just the whining, I'd start with the fluids, then move on to the CV/axles and main driveshaft.

Re: Diff noise?? from the 04 RS6
 

Just hit 85k kms, had the big service done.
Will check rear diff fluid colour, see whats up.
It is strange, just noise, no vibrations.

Re: Diff noise?? from the 04 RS6
 

Sounds like it could be gear whine. What is "the big service"? Driveline fluids replaced?

Re: Diff noise?? from the 04 RS6
 

Just checking the records, no fluids changed. Rather than dragging this thread out I'll check the diff first and post results after. Stay "tuned"