changed the differential oil, still no improvement

[Raffi Tomassian <tomassian@glaserworks.com>]

Hi All,

A week ago I asked for help regarding the whining noise coming from the
rear of my car ('87 4kcsq) at around 30mph, gradually thinning (the whine
that is) untill I reach, say 80mph, when I don't hear it any more.  The
replies I got directed me to the rear differential, so I armed myself with
some Valvoline 80W140 GL-5 (They never carry and only order RedLine in
cases of 12 where I live), drained the old, probably '87 diff. oil and put
in the Valvoline stuff.  The situation now is unchanged; the whine is
seemingly there to stay.  Any suggestions where I should check next?  At
the advice of a friend I clutched several times while doing 65-70 on the
interstate to check if the noise would go away or change; supposedly if the
problem is in the differential the whine should change if it is disconected
from the engine (therefore clutching) with no audible result.  Any thoughts
on that?  Suspecting the wheel bearings somehow does not make sense to me,
since to me the noise comes from the middle of the car.

Thanks, as ever, to all respondents,
Raffi