Is it possible I could have warped diff housings?
I've been battling a leaky rear gear diff since I built this car. I've rebuilt it 3 times. The last time with new paper gasket and no large O-ring. Went on vacation for two weeks after rebuilding it, and then came back to find some oil on my belt and dripping down. I've just about had it. Made sure not to overfill. Not to overtighten or undertighten the 4 screws....urgh...
You must be overfilling it. I've only built a few gear diffs in my time -
Spec R Yokomo - no leaks
TC6 - no leaks (but nowhere near as smooth as an Xray diff)
T3 - no leaks, silky smooth
T4 - ditto, as above