need help diagnosing drivetrain problem on 90q20v

[Dan Simoes]

20vers, I know it's not an SUV, but maybe you can help :)

I'm a little baffled on this one and figured I'd check before ripping
things apart.

The patient is a 1990 90q20v.  Symptom: when making a tight right turn,
you could clearly notice the left rear tire dragging/scrubbing.  I
thought perhaps the rear diff had locked, and asked a shop to check it,
no problem found.  I chalked it up to a wheel bearing and parked the car
as I was trying to repair the driver's seat.

A couple of weeks later, my father had a car accident and needed to
borrow mine, so I threw the seat back in and let him have the car.  He
called me to report that the ebrake was not releasing and he could feel
the car dragging.  I checked it and manually freed the caliper on the
left rear side.  He brought the car back again in a day or so and said
it was still dragging.  I drove it and confirmed this.

I put the car up on blocks, removed all 4 wheels, and was hoping to see
3 wheels spinning.  Instead, I see the fronts spinning and nothing
happening in the rear, nothing in the prop shaft either.  WTF?  Bad rear
diff?  Bad carrier bearing in the shaft?  With the car running and in
gear, I can "help" the prop shaft and see both rear halfshafts turning,
so I know the diff is not seized.

Now that I'm up here typing this, I'm wondering if the Torsen center
diff is not sending power to the rear because there is no traction.  I'm
not positive about this though.  Assuming the rear is OK, that brings me
back to either a bearing or caliper in the rear left.

Another weird thing - the rear diff never worked although the switch
lights up when you press it.  Well, right now the ABS off light is on
and the green LED indicates the rear diff is locked.

I'd like to get this sorted out as I'm thinking about selling the car
anyway.  As you may have read, we picked up a used Volvo 850 for my wife
and I'm driving her 99 Jetta TDI which I can't seem to sell due to the
unique color (that's OK though, 49mpg suits me just fine right now in
this economic climate).  Consider this an offer to sell the 90q, email
me for details.

Thanks for any suggestions.

| Dan |