Hi y'all

I have a peculiar symptom on the '87GL 2WD while coasting in reverse I'd
like some light shed upon.

Scenario:  Clutch disengaged, shift to reverse, clutch engaged, driving in
reverse, clutch disengaged (no brakes, in attempt to coast backwards), REAR
TIRES LOCK UP!!

Now, to me this sounds like a gearbox problem. At first I thought it may be
the rear brakes locking up, but I doubt it very much. I find the gear
shifter a little stiff in attempting to shift to neutral after the
occourance.  Could it be the diffs? As long as I keep the engine engaged to
the gearbox it operates normally in reverse. But as soon as I push the
clutch in, WHAMMO! All the forward gears shift like a dream.

Any input will be appreciated,

Ken