Lazy man's way of filling Diff on a 75 Valiant
I put one side of the axle, brakes etc. together, bolt the wheel on,, drop that side on the ground,, and use a large funnel to pour the lube down the open axle tube, before I put the other axle in, then finish assembly..
Doesn't work on a "C" clip diff, tho.. lol
hope it helps