About the bearings, how do you torque them since they appear to be "slipped on" i didnt see any screws to torque them down ?? When i removed my axle shaft i noticed the there were not gaskets in the wheel bearing retainer or on the actual diff yoke, is it really necessary to put gaskets

One more question, when i pulled out the shaft there was a wheel bearing,wheel bearing retainer, but no axel shaft seal. I bought this differencial about 4 years ago from this guy on Craigslist, he said that the differential is in good shape, but from what i see its missing the gaskets and the axle shaft seal. Are they really necessary ? Ho