[A bones]

If you used regular heavy gear oil. drain it out now! The right stuff can be had from the Model T suppliers. The stuff they sell 'down the street' will harm the babbit in your rear. This may result in loss of proper gear mesh and also the loss of trans braking ability.
When first I serviced mine, I bought it from Bob's. All was fine.

Years later I just grabbed the hose in my gas station. Filled her up. Then after several hundred miles the rear went South.