trans fluid leaking out of shaft connecting to u-joint.

What is your question?

i'm just using his login to ask this: it doesnt leak for awhile thn all of the sudden most of the tranny fluid leaks out. it's dripping out of the shaft coming from transmission to the u-joint. is there a seal in there? this truck is a chevy 1983 model c10. the repairpal doesnt go back this far. thanks in advance.