vibration at 80 mph

["Stefan Richter" <Stefan13@worldnet.att.net>]

After a recent alignment and tire rotation/balance, I took the S6 out on
the turnpike for a test drive.  At about 80 mph, the car has a faint
vibration which I think originates in the center or back of the car.  The
steering wheel and shift knob do not vibrate.  I have heard discussions
about the driveshaft support bearing, but I don't know how to check it with
the car on jackstands.  Any other known sources for this problem?  The car
is still under warranty, and I would like to be able to talk the talk when
I bring it in, only to be told that "we couldn't reproduce your vibration".
 Thanks in advance.

P.S.  I still have a barely used THULE roof rack with shield for sale that
will fit any A2 VW.

Stefan Richter
95 S6
96 Jetta GLX