HELP! Rattling from rear

[Robert Bauer <102263.2714@compuserve.com>]

To add to the list of problems with my '88 80q I now have a bad vibration from
the R rear.  Here is what happens: Last night I was driving home and when I let
off the gas I heard and felt a vibration.  It seams to be comming from the rear
of the car.  It sounds like the drive shaft is bumping something.  I checked the
exhaust and it seems to be fine.  I don't think it's the gearbox because I'm not
getting any feedback throught the stick.  Now this morning while driving to work
the same thing happens but now I get a new vibration that feels like the R rear
is flat.  The CV boots aren't cracked.  I did notice that the seals on the rear
diff are leaking a little.  I haven't checked the oil level in the rear but I
will as soon as I get home.  Don't think it's the wheel bearings because it only
happens when I let off the gas.  The dealer told me the first noise may be the
bearing in the drive shaft which is not available, it only comes with the shaft.
Any help would be appriciated.

TIA
Robert Bauer
sick '88 80q
102263.2714@compuserve.com