I have a 1992 Suburban 4x4, 270,000 miles. I think it all started with bad u joints, the drive shaft had been vibrating periodically and then finally the rear one broke and I had to replace it on the side of the road with a hammer which kind of bent the end of the drive shaft where the ujoint go in so the u joint was a bit tight. I found that out from the shop that later rebuilt my tranny. then one day i put it in drive and the rear end went bang and started rattling like there were rocks in it. Long story short. I can put it in drive and it goes nowhere and the rock grinding sounds like its coming from the passenger side rear axle tube. Took the differential cover off and found a few small slivers of metal but i cant see any thing broke. when I turn the rear drive shaft by hand it catches a bit every few revs. I drive it around in four wheel drive and there isnt any sound from the rear at all. Its my beater so as long as it drives...However I've been driving it around like that for about two years and It's probably time to fix it. Any Ideas? And how long do you think I can drive it around in front wheel drive? I have to wait for the 4x4 to engage before I out it in gear at start up other wise it grinds away until the rear drive line stops spinning after I put it back into park.