Driving to the shootout this morning a vibration occurred, I thought it was the road but it quickly became exponentially worse, I signaled to the edge and the tires locked up. Seemed the locked up tires bounced around it didnt seem to be a total rear end lockup like described by tcase failure. This happened in a matter of about 30seconds. Like others I thought flat tire, everything checked out and to boot I was on 80-90. I took my chances and forced the car back onto the road. The problem cleared up and I made it 2 miles before it started again. Thank god I was at an exit, got off, let the car set 15min an was able to drive it 15miles to bass pro to wait for a trailer without another problem.

92 awd 6/4 No prior noises problems, t case has never leaked, drained tcase tonight and found no shavings ran a magnet thru what I collected. Had car on jack stands rear end seems fine. 1 thing I notices is the front differential is not acting like an open diff. Even with the car running in gear on jack stands the driver tire is the only front tire that spins (both rear spins same direction), when I stop the driver tire the passenger tries to turn but just kinda jerks a little.

Im thinking the center differential is bad because the diff is not acting like an open differential. I took the fill plug out of the trans and got heavy metallic flake in the oil (redline mtl mt90 blend maybe 6k miles on it). What I don't get is the whole problem seemed to stem from the rear end (which I didn't have time to drain tonight). Whatever the problem is I can currently drive the car without problems, its my garage queen only drove for diagnostic reasons. While I drove to bass pro it seemed that I was getting a periodic bearing grinding but it seemed to be coming from the rear end.

Wanted some suggestions, I don't want to throw a bunch of money at the car, I'm looking to isolate the problem.[DOUBLEPOST=1408396738][/DOUBLEPOST]Drained oil out of the rear end and replaced with new. Oil still had an amber color and collected no metallic flakes from the oil with a magnet. I'm leaning on center or front diff... thing I don't get is I have not launched the car at all. Either I'm looking in the wrong place or the previous owner was hard on the front/center diff before I bought the car. I was cruising at 70mph when the problem occurred.

Could the problem be the viscous coupling? I have an extra viscous coupling but my extra center diff is broken.