Greg Rogers

I have 2 leaks on the th350 in my 1970 Vista. A small one at the kickdown cable which I think I can fix easily. But the 2nd one is bigger and seems weird to me. It is leaking thru the inside of the yoke and coming out by the u-joint. Its not leaking around the seal but apparently goes thru the inner splines and thru the inside of the yoke. Am I missing a seal or something? O-Ring? Thanks for your help...

MDchanic

There is a vent in the middle of the yoke, and should be an O-ring on the outside of the output shaft that slides in the smooth portion of the yoke, before the splines start.

The O-ring is supposed to keep oil out of the yoke, and the vent is supposed to allow the yoke to travel in and out without creating an air-hammer effect.
The splines of the output shaft are supposed to be lubricated with grease.

If the O-ring wears out or is not replaced, then oil can get past, and once it's in the yoke, it can leak out through the vent hole.

Later (I believe) models did away with this system, in favor of eliminating the vent hole and having one "missing" spline, which allows air to pass through into the transmission, but make it hard for oil to get through.

In general, if your yoke has the "missing spline," then you can braze up the vent hole without a problem (that's what I did). JB Weld can be used, but will not last forever (that's what the PO did).

- Eric

Greg Rogers

Thanks Eric, That makes sense. I have seen the "missing spline" before. I will check it out.

Greg Rogers

I checked it out and you were correct Eric, it does have the missing spline and also the vent hole. I was replacing the U joints anyway,( 177,000 miles and still the original U Joints) so I brazed up the vent hole.. Thanks!!

MDchanic

You're welcome!

Mine's been working fine like that for a couple of years now.

- Eric