Help! Binding Driveline - Any Ideas?

[Exaran]

My xmod's always been a little unstable, and LOUD, but I figured that was normal. One of my friends finally got a xmod the other day, and his is MUCH quieter, faster, and a lil more stable.

After observing it a little closer, I saw that my drivers side rear wheel was locking up every time my car lost traction (which happens VERY often). When I run it off the floor (no load), sometimes only the passenger side wheel spins. If the driver side starts spinning, it stops as soon as I let off the gas while the passenger side continues to coast for a second or two.

I figured I must have gotten some dirt in there, so I dissasembled the whole rear, even removing the bushings and taking apart the diff, and cleaned and oiled everything...

The problem is still there!!!

When I tested the rear in various states of half-assembly everything works fine. Everything spins freely without noise. When I put it all together, however, the binding returns. If i hold the rear section in my hand, and hold the drivers side wheel, the passenger wheel and diff will spin for a few secs when i give them a whirl. If I do the opposite, I can feel resistance and get no free spinning.

Everything has some slop, and nothing looks like its rubbing on anything. There doesnt appear to be any flash on any plastic parts either.

The thing I wonder about is the inner part of the driveshafts (the parts that go into the diff) the side that works is metal, and the bad side is plastic....

Can anyone help shed some light on my prob?