Which Yoke and leak questions

I can tell you what to do to fix it, but it's not a widely accepted solution.

First make sure the surface of the yoke doesn't have enough pits in it to leak no matter what. (polish it with crokus cloth if you have to.)
Take the spring out of the inner side of the sealing edge and note where it screws into itself. (thats how it makes a solid circle)
Unscrew it from itself and cut about 1/4 inch of the off the open end of the spring.
Twist it counter clockwise first and let it screw itself back together.
Put it back in the seal, use Mr Gasket brush on sealer (That dark brown stuff) inside the ext housing seal surface area (not on the seal) and put the seal in.
Putting it in the housing instead of on the seals makes it fill imperfections in the tailshaft surface as the seal goes in.

If it isn't leaking out the vent in the yoke (or around the yoke plug itself) and the yoke doesn't have a deep groove this works almost every time.

Basically it just tightens up the lip sealing edge on the yoke.

It's an old trick from the trans business.