Im not sure the correct term, but when i press the clutch, the nipple that pushes in the plate on the transmission is leaking. How and what do i need to fix it? Thanks for the help

 

I think it is called the slave cylinder

 

Found a new slave cylinder. Just want to know if it the 13/16 or a 3/4?

 

Not sure...you need to tell an auto parts store (or better yet the dealership) what truck you have and see which one you need. Looks like '81-94 use the same slave cylinder. Without knowing what year your truck is nobody here will be able to help.