When you get a chance, check out your 4-speed for a possible "crack" failure. Vince Falter at his most excellent Fordgarage.com site addresses a crack modus which occurs due to mis-positioning of internal components. See
https://www.fordgarage.com/pages/aatranscracks.htm
Another common cause of a crack is the classic "smile crack" which is caused by water getting in through the top of the transmission. Unlike the Model A gearshift lever, the AA lever does not "shed" water. Instead, the water follows down along the shaft, bypasses the ball, and keeps going to accumulation in the bottom of the tranny.
This can build up and freeze. And the crack is on the "front" edge of the transmission case just ahead of the drain plug. It encircles completely from one side to the other - hence the "smile."
I had an AA truck I took out from under a barn in Amherst, NH. The barn was not exactly "hermetic" a cover. Truck had the 82A square body but the fabric roof had rotted out, and the former owner for some reason had removed the top of the transmission. I saved all the gears and internals but the case was junk.
Again, good luck. I just recently bought a 4 speed tranny for $50 locally - so they are out there if you get in trouble.
I see someone has mentioned the AA-Forum.
Joe K