4kq-whining noise

[William Murin <murinw@cs.uwp.edu>]

Colleagues and friends:

My '87 4kq has just celebrated its 151,000 miles birthday.  Unfortunately 
it has learned a new noise.  Appears to be right rear end or at least 
rear end in origin.  Best way to describe it is a whining sound when 
downshifting/decelerating.  Noise does not seem to exist in the 
acceleration/upshift mode.  Observations and best guesses are most 
apreciated.

Thanks.

Bill Murin

PS:  Dont think its tires or brakes.