[Biturbos4] A whine from the rear

[Chris Newbold]

No, no, not from my son in the back seat :)

Just shy of 65k miles, and I'm starting to notice a whine originating
somewhere in the rear. The whine...

  o is loudest between 65-70MPH
  o is unaffected by gear: 3rd, 4th, 5th or 6th and the pitch is identical
  o is unaffected by steering inputs
  o is strongly correlated to throttle inputs:
     - it stops if you gently lift and coast
     - it stops if you dip in and accelerate
     - it returns in steady cruise

The only things which satisfy all of these observations are:

  o rear differential
  o center drive shaft bearing (do the B5s even have these?)

I haven't heard of any premature differential failures in the B5 S4, and
it's not like it's very highly stressed (compared to some other
comonents). But, hey, there's always a first time.

Anyone have any thoughts or comments?

Keman, I don't know if you're still around, but did you see any such
failures during your time in the shop?

-Chris
2001.5 S4 Avant 6spd