the problem is usually the leak that would need a seal in the axle to fix is from the hub side through the bearing pack and not where the block bolts to the brake backer plate
if you have a leak at the hub side the bearing lube has left the bearings and a seal placed in the tube to stop the gear lube from leaking will starve the bearings , i know you cant leave the oil leak but starving the bearings and the elims will fail
only fix is remove and replace either with another moser elim or better fix is something else like the strange ..or forget all those and convert over to the ford style weld on axle end eliminators
and easiest way ive found to remove those mosers is to cut them off then score the inner race and split it with a cold chisel and it will slide off