Trans and Diff Fluid

["Mark Hahn" <hahnmgh63@earthlink.net>]

  In the rear diff of a Quattro you definitely want a gear oil in the 75W90
range or something close that meets GL5 specifications which most out there
do.  I am a synthetic fan and use either Redline or Mobil 1 gear oil.  The
transaxle is a different matter.  This calls for a GL4 which is easier on
the syncros but harder on the gears and bearings.  The GL 4 can be had from
Redline in synthetic in their MT90 oil and in some conventionals but it is
hard to find at your local autoparts stores.  If you do a lot of city
driving I would recommend going with the MT90 (GL4), if you don't I would
use a quality GL5 (synthetic preferably).  I have used a GL5 in a Porsche
944 and a Turbo for over 60K in each car without any signs of problems so
that is what I'm about to put in my 5000SQ.  Good luck, MGH