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...
I had the same experience with mine. I solved the problem initially by using aw grease on the large o ring.
I have since invested in a digital scale to weigh as I fill te diff and that has solved my leaky diff issues. I found when using the scales I was putting too much oil in without using them.