I agree with Kevin that the gasket isn't probably an issue. More likely a failed axle seal. But (
a big but), have you checked your fluid levels in the axle and transmission??? If you still have the original torque tube setup, and the seal in the transmission end of the tube has failed, it will allow transmission fluid to travel down into the rear axle causing it to overfill and create excessive leakage/failure of the axle seals. Just offering another thing to check to help confirm or eliminate as a possible cause. Either way, you need to replace that axle seal for sure.
