5kquery, rear diff

[geo <gamills@ns.sympatico.ca>]

Is it normal to have a hum a.k.a. whine, you know the sound, in the rear
diff on these at around 100k miles?  I have driven a lot of  RWD's and
come to expect it as a normal aging feature.  I have about half an inch
of play on the prop shaft at the back.  This sound starts very low at
less that 60kpm (30 mph), increases in frequency and is most noticeable
between 60 to 80 (35 to 50 mph), and disappears at about 110 (65 mph).
This is all under throttle, disappears with no throttle, your standard
rear diff test.  No clunks.  There are no leaks but I have not checked
the fluid yet (snow on the ground, no lift available, etc.)  This sound
seems to be getting louder but I may be just 'tuning' into it.  Doesn't
seem to be any play torquing the rear wheels back and forth laterally
with the rears off the ground, but that was a test I used for the solid
axle whereas this is not.

If push comes to shove and I need a rear diff, what years are similar?
Is it a undo the prop, pull the axle shafts, unbolt the diff R&R?  My
Haynes is not for the quattro, just the FWD.

Geo

P.S.  The lake I live on is now ice free!  Whoopee!  First time in the
almost 20 years I have lived here this has occurred before the end of
March.  The black ducks are out there figuring out who's who, or which
one is the quackiest, I think it is a male/female thing.  Spring has
sprung!