Rearend Blues! (kinda long)

[90'5.0 Conv]

Ok, I don't know what else to try. I went ahead and retorqued the pinon nut back like I had it before. All the way until there was no play, then about an 1/8th turn. I put the ring gear in and shimmed it over to the left just a little. Then, I torque down the caps just a little bit and the darn thing locks up so I shim it over again and torque the caps just a bit and no matter what it locks up. I kept moving over till I hit about 4 shims(all small), and nothing. If i leave it loose, it seems to move fine but as soon as a tighten the caps, especially all the way to specs, it will lock up. I even checked the wear pattern when it was moving and it had a heel pattern on one section and a toe pattern on another and a good looking pattern somewhere else. What gives? I'm about ready to call it quits. Anyone know what could be going on here?

Thanks for your replies, James