Silverado 1500 4x4 Rear Axle

[steveo00]

I have a 2000 chevy silverado with some major brake problems, i.e. brake pistons sticking, calipers corroding to the point of disappearing(!), brakelines corroding and bursting and the dustshields in the rear rusted out (nothing left of them. This condition was persisting even after I had "professionals" working on these brakes. Well, after the 2. almost accident (the brakeline burst again!) I decided to do the repair work myself. I was shocked to find the underside of the truck in such deteriorated condition. Must be metal from China! Besides the new "very effective" roadsalt that DOT now are applying to the roads so that everyone can be "safe" ! I could have killled myself and others operating this vehicle!

Anyway, replacing the rear brake dustshields require that you remove the rear axles. In the process of removing the axles I noticed that the rear differential hub seemed to be dropping in relationship to the wheel axles. A stiff axle is supposed to be in a straight line, from the end of one wheel axle through the differential and out to the other wheel. So you take a piece of line and "eye" the position of the axles through the differential and and should find that the center of the axles line of with the line you are holding on to. But what if it doesn't? And the direction of the axles going out frm the differential is going up? Does that mean that the differential has dropped from that horizontal line? It hit me when I raised the truck off the ground, removed the wheels and turned the wheel hubs and the axles were sticking at a certain point.I guess this could happen when you raise the truck by supporting the rear axles instead of the frame, not so in this case though. Can anyone give me a clue as to why this sticking occurs. I would appreciate any suggestion. Is this an indication of a defective inner or outer bearing, does it have to do with the spider gears. There was significant amount of metal dust/shaving on the magnet and the inside of the housing was totally balck from it. Thanks for any help