I got a 97 f150 4x4, 4.6 and I had the shop replace the seal 3 times and it's still leaking, the seal were the driveshaft goes into the t case, I call it the slip yoke seal, they said the bushing inside looks good, there doesn't seem to be a whole lot of play in the driveshaft, it doesn't seem to leak a whole lot, I'm about ready to just forget about it and just run it, they put a seal from oreillys in, it seem to be leaking out of the bottom hole on the seal

 

I have 4x4, but not in that vintage truck.
And I have that vintage truck, but not in 4x4

"Leaking out of the bottom hole of the seal" ?? There is a hole in the seal, other than the obvious shaft hole?

The T-case probably has a vent tube or vent valve, is it plugged with road crud, so when the T-case gets hot, the air expands pressuring the case, pushing oil out through a seal? Just thinking here.

 

Yea it's leaking out of the bottom hole of the seal

 

Sounds like a bad main bearing

 

Yea but the mechanic said there wasn't any play in there, if the bearing was bad wouldn't there be an excessive amount of play on the driveshaft?

 

Does the yoke have a grove worn in it from previous seal contaminants/dirt? If so replace yoke on drive shaft at your local drive line/drive shaft repair shop.

 

It could be pressure build up in the t-case. Some of these trucks were prone to having transmission fluid leak into the t-case. What's the fluid level look like in the t-case?

 

Slip yoke was polished, I did check the t case and it did seem a little over filled, when I went to check through the filler plug some came out

 

This is an old "clunk" problem. Read some of my old post.
I never could fix it so I had to remove the ESOF and the transfercase and yoke screwup and go with a aftermarket "atlas" transfercase and redesign drive shaft.
This was serveral years ago. It has worked flawlessly since.
good luck.