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How to ID fualty mount/driveline components

I've been trying to ID the source of the problem that I am seeing on
occasion with the '91 v8q/5-speed.  It seems as though when one drives the
car in spirited fashion some sort of driveline shudder develops when power
is applied, apparently in the rear of the car.  In the past I thought it
might have been some characteristic of the Torsen rear diff with mismatched
rear tire diameters, but I have confirmed that this is not the problem by
installing a completely different set of wheels & tires.  My next suspect
was the propshaft carrier bearing housing ... which is buried behind a heat
shield on the V8.  

Well, I finally got around to pulling the heat shield (I'm glad I could do
this w/o having to drop the exhaust system) and everything looks OK.  There
is a little bit of rotational play in the propshaft, but it doesn't seem to
be more than what I've seen on other cars.  It does appear that the bottom
part of the carrier bushing is compressed, but it is intact.  I've never
seen this fail ... does it harden or tear apart?  

I've seen people write that bad tranny or diff mounts can cause this sort of
problem ... The tranny mounts are pretty stout and the rubber seems to be
pretty pliable under the cap.  Here again, the only failures I've had are
where the guts of the mount disintegrate, so it is obvious that they need to
be replaced.  Is it possible that a good looking mount could be bad?  How
might I determine this?

Final question ... the fiche shows two different P/Ns for the propshaft,
with the difference being a yellow vs green color mark ... well, I see no
mark of any kind on the propshaft, CVs or Carrier bearing ... any
suggestions as to where I might find one?  

TIA for any thoughts!
Steve Buchholz
San Jose, CA (USA)