Out of curiosity, what fluid is used to service the front, center, and rear differentials? I have a RS5 and I've seen some postings that mention the rear sport differential has two compartments; one for GL5 75w90 gear oil and one for ATF. I haven't come across any official documentation from Audi and I haven't seen anything for the center and front differentials.

As an aside, I think stuff like this is why it would be nice to have a unified B9 forum. It would be nice to have single threads for, the speaker upgrade posts, interior, modifications, etc. instead of having to search between the two forums.