1978 C20 Drive Shaft Center Seal

[Robert Crandall]

I am not finding a center drive shaft seal for my 1978 C20. Possibly because I do not know what to call it.

The truck has the granny gear 4 speed transmission and a 2 piece drive shaft. For many years adding grease to the fitting on the splined center of that shaft only puts the amount that I add out the seal. None goes to the splines. When the truck was new (and for many years after) grease would come out of a hole at the opposite end of that splined section, letting me know when the whole length of the splines is greased. I'm getting ready to take the transmission out to replace the crankshaft's rear main seal. I want to try to change this seal as a "While I'm at it..." task.

Can anyone identify this seal, or direct me to where I can find it myself?

Thanks!