Help diagnosing diff problem

[JThiessen]

Guys, I've been chasing a gremlin in the rear diff on my 8T for a while. A month ago, I tore down the rear end looking for something that would cause my rear diff to lock up. I completely pulled apart the diff, installed new spider gears and bearings, shimmed it, and re-shimmed it. Prior to installing it, everything felt fine/normal. Now after I get it all back together, one side wont turn (RH side when looking at truck from behind). The LH side turns fine in both directions. I can get about half a turn at the wheel on the RH side.
Almost makes me think I might have used the wrong length of screws to mount it or something - but I'm still running the stock screws that came in it.