Driveline problems 90q

[David.Payne at brinksinc.com]

OK guys, this is starting to get serious.  I've had some drivetrain lash
problems with this car ('89 90q) since I've owned in (just over a year,
about 12k miles).  Now I'm picking up some scary noises as well.  When the
drivetrain has reverse torque, i.e. when in reverse or under engine
braking, I get a substantial 'ring' that seems to happen once every
driveshaft rotation.  The best that I can tell, the noise is coming from
the tail housing of the gearbox, right where the torsen lives.  I plan on
getting under the car tonight and putting a load on it in reverse and see
if I can pinpoint it a little closer.  In addition I have a new knock that
comes from the rear end at low speed, under 15 mph, again while under
engine braking like when coming to a stop.  I haven't been able to
duplicate the knock by driving in reverse, and the knock only seems to show
up after driving for 15 mins or so.  The knock sounds like the diff is
trying to divorce itself from the rear subframe, you can hear it and feel
it.  This car needs new front diff mounts and g-box mounts, but it has
needed them for a year, it didn't just happen.  Both the g-box and diff
fluid was changed when I got the car and I check both this weekend and they
looked OK.  If anyone has any input please let me know, I'd need to get at
least one more year out of this beast and I have invested to much in
getting the CIS and suspension sorted out to abandon it.
Dave.