Technical U-joint question: what is this stuff.....

.....and what is its purpose? It appears to be some sort of plastic that was injected after the caps were installed. There is a bubble of it protruding from each side of the cap ring, and it filled a groove within that ring. The caps are smooth sided, but there is a witness mark where it contacted the plastic filling the groove.

 

Just how factory gm u joints are held in. Some sort of plastic

 

That takes the place of the internal snap ring's that the replacement u-joint comes with. You're supposed to heat the fiberglass with a torch to burn it out before you try to remove the cup's... Atleast they come out easier if you do it that way.

It stink's like Hell, though!

 

I've always heard about melting the plastic , never have done it , never had a problem...

 

I've personally found that cleanup is easier if you drive them out without heat myself

 

amazing to find one with plastic still in it, after 50+ years of use! I thought we replaced all of them

 

they pop when you heat them...

 

I've never dealt with u-joints that had a retainer for the caps. I thought chasing needle bearings was always part of the process.

 

It's not to hold the cap on the u-joint, it's to hold the cap in the yoke.

 

Broke my dads vice in half trying to press my s ten u joints apart. Neither of us had any idea about the plastic seal. Heated it afterward with propane torch just to try to loosen it up and these plastic snakes climbed out of the yoke... Freaked us out. This was all prior to people having the Internet.

 

Lol. Yep those plastic snakes were a regular thing back in the ‘80s.

 

My T Bucket still has both of the factory u-joints, held in by plastic. They still feel as good as new. The driveshaft came from a 1979 Malibu. It’s been shortened obviously.

 

Just a wonderful idea GM had there. Not sure who else did it.
I just stared at the plastic and called the Chevrolet service center in town and asked “what the heavy do I do here”?

As was mentioned before they told “do it like you’ve done them before”.

 

Hmm, interesting. I guess I've never seen it before because I'm always working on old Fords and Mopars. These U-joints did have the C-clips on the inside of the yoke as well, so I guess they were doubly secure, or might have been replaced at some time in the past.

 

oh yeah...that one has been replaced, the plastic is only in the yoke. When you do an original, there won't be a groove for a clip, there will only be a groove with plastic in it

 

I've never had much difficulty disassembling them, however getting the plastic back in the yoke on reassembly is a major PITA.

 

I think if you get it cold it will shrink right up, or it could have been something else.

 

The same seal was in the front bearings used in AIR pumps from 1966-on. Since they were in an aluminum housing they were easily broken when trying to repair one…