I agree the axle seals need to go and do check to see if the unit is over full. Also If you are talking original 'torque tube' the problem can be, that trans oil is getting past the seal at the front of the torque tube and running back to the diff, you'll need an 'okie bushing' to fix that. I like to keep my diff slightly low on oil so as not to lead to the axle seal leakage. And, replace the shoes, as they are inexpensive if you shop around.
