Rear end locking up

[William Berglof]

I'm not even sure I'm in the right place. But here goes anyway, I have a '94 GMC Sierra K1500 extended cab short box manual transmission. The problem I'm having is, the rear end is locking up. Only when I make a left hand turn or on an uneven surface when the drivers rear wheel has less weight, and locks up. But primarily when making left turns. It will lock the rear end to the point of skidding tires on dry pavement and sometimes even stall the truck. I have had the rear brakes looked at, adjusted, drums turned, new springs installed. I have had the rear diff looked at by GM professionals as well as differential experts. No one can figure out the problem. Thank you in advance for any help. 

[richard wysong]

did they pull the cover to look at the gears? sure sounds like the spider gears are the problem

[William Berglof]

Yes, they did pull the diff cover. Then very carefully and slowly rotated the wheels while inspecting the internals. Nothing seemed out of place. 

[Brian Lindsey]

your axle is probably moving side to side , im guessing only , but i would say you have a bad axle or bad bearings for the axle

[RayRob65]

I had a 1990 GMC 4X4 work truck that would lock up and finally had to replace the locking differential unit in it.