Rear diff. locked all the time (was 90 CQ Drivetrain Slop?)

[ecschott@juno.com (Edgar C Schott)]

 Bruno Walter wrote:
> My father recently purchased a 1990 Coupe Quattro, and it has an
> excessive ammount of slop in the drivetrain.  When pulling away, one
> must be extremly gentle in order to avoid a clunk.
>
> Likewise, it is impossible to accelerate through the gears quickly
> without being greeted by the same clunk.

Gary Erickson wrote:
>I have an '84 4kq that makes the same clunk on hard acceleration, and
>I'm 99% positive from the location of the noise that the rear diff
>mounts are dead.

I have been fighting with the same symptoms that Bruno wrote about.  I
shelled out the  $80 for the diff mounts, even tried dropping in a used
rear diff, all to no avail.  

Some history on my '84 4kq is that the previous owner had the diff. side
seal replaced by a Nissan/Volvo dealership and apparently they
re-installed the shim on the lock mechanism improperly such that the
differential was always in the lock position.   The car was driven daily
around town and on the highway for about 3 months.  

My questions for the list:  
What damage is likely to result from driving the car with the rear
differential in a permanent lock position as described above?

When I have the rear end up in the air, hand brake engaged, and I turn
the drive shaft by hand, I can simulate a "clunk."  A reputable shop has
told me this is normal play, but I wonder.  Should you see movement of
the inner CV joints (relative to the half-shafts which are held
stationary on the outside ends by the engaged hand brake) when turning
the drive shaft by hand?  Other than opening up and cleaning an inner CV
joint, how would one know if it's bad?

Chuck Schott (ecschott@juno.com)
'84 4kq