JLM,
I don't believe there is a rear seal, just a flange or deflector between the yoke shaft and the inside of the cast housing that has the speedo gear in it.
Also, two of the bolts that hold the tranny to the bell housing, the two that are accessed from the inside of the bell housing, go all the way through to the inside of the tranny case. You must put sealant on the threads of these bolts or they will leak like crazy.
I believe the speedo drive gear presses off but I have never messed with that.
Kent
