Subject: bad driveshaft on V8?

[C1J1Miller@aol.com]

Jim Dhillon wrote:
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"I get a thump in the back when my tranny shifts occasionally on my V8..
could this be due to a bad u-joint on my driveshaft? I reached under my car
and turned the shaft back and forth by hand.. there seems to be some play
before the gears start turning on each end. Any place else I should check
before digging into removing the exhaust and driveshaft for a looksee?? 
How can one diagnose a bad CV joint? I get some vibration at highway
speeds. "
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The "thump" in the back is typically bad rubber support mounts on the rear
diff.
The driveshaft on each of the quattros I've owned had some play as you've
described.  There is also a support bearing that keeps the driveshaft in line
attached to the body.  These can develop too much play and may cause some
vibration.  I'd recommend putting a little grease into each CV joint on the
driveshaft to see if that takes up some play.  There may also be a greasable
fitting at the U-joint.  Vibration is often a tire issue; make sure they're
properly inflated and balanced, and not unevenly worn.  Could also be from
worn bushings (control arm or subframe).
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"Also, when I drive over a speedbump, I feel a bumping noise as if something
is not quite tight. Any ideas on what might be the cause - it feels like it
is in the front end somewhere but I have checked wheel bearings and tie rod
ends. All seems ok."
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Sounds to me like upper strut bearings.  How many miles on the car?
HTH, Chris Miller, Windham NH, c1j1miller@aol.com
'91 200q => http://members.aol.com/c1j1miller/index.html