Technical Question - Pinion Seal

Technical Problem:

I changed the rear pinion seal on my 1951 Mercury. After I put everything back together and drove it around the block I noticed a leak where the front drive line connects to the transmission. Common sense told me that the front seal may have started leaking when I moved the drive line in and out. After taking a closer look I noticed transmission fluid leaking where the transmission yoke connects to the drive line yoke. Absolutely no fluid leaking from the seal.

Question:

Can fluid leak from the the center of the yoke where the short shaft inserts into the transmission. I'm attempting to attach a photo for reference.

Thanks

 

Some yokes have like a freez plug in them,if you pumped it all the way in to ****** before pulling it back out to the right spot to hook it up to the rear end,it could of made it leak. It's not under PSI other then when you push ****** yoke in,the oil seals it some and get a little psi for a sec. If it keeps leaking,you'll need to hit the plug back in better I think.
Lets see what others have to say too.

 

I removed the driveline and took it to a shop who explained that there is a small vent hole at the center of the yoke. For unknown reasons trans. fluid started leaking from this vent opening. My only alternative was to have the hole welded because it didnt serve any significant purpose in the first place.

Thanks for the help.

 

But it DOES serve a purpose and that is why it was there. As suggested in post #2,
the normal movement of the yoke into and out of the transmission creates a piston/cylinder relation ship between the yoke and the transmission output shaft.

The close fit of the splines between the shaft and yoke do not allow air to easily enter or exit the "cylinder" as it's volume changes. THAT is why there is a breather hole in the back of the yoke. Some vehicles, IIRC, have a small hole bored into the end of the ****** shaft, and another small hole cross drilled into that further into the trans, to permit that movement of air. In that design method, the is sealed at it's end. But that apparently is not the case with yours. Welding the breather hole closed is a mistake.

Ray