I just bought the front peice of a 2-piece driveshaft from a junkyard. The male spine end that is pointing toward the rear of the truck has a cap with a grease fitting. Is that cap just threaded on?? What is the official term for the cap?(I was thinking of getting a new one)

 

If it's anything like my '90 then those caps are just lightly pressed into place. You can knock them loose pretty easily. I don't know the official term, sorry. Why do you need to replace them??

 

It's just a seal.