Th400 throwing oil out the rear seal?

[americanmusc1e]

I rebuilt this TH400 a few thousand miles ago. I'm for sure it's leaking out the rear seal. I can put it 1st gear up on jackstands and watch a bead of transmission oil work it's way out the seal. The entire underside of my truck is coated in trans fluid. Very minimal drips on garage floor.

The first thing I did was pull the extension housing and replace the bushing and seal with a spare that I had. Seemingly no change. I then put a dial indicator on the yoke to make sure it's not out of round and it has ~.020" of wiggle in the bushing/splines but almost zero out of round.



This yoke is suspect. It's an ebay special and it lost the freeze plug out the back a few thousand miles ago so it got the grey silicone and washer freeze plug replacement. Though it's not leaking out the back of the yoke. I've found a really nice sonnax replacement yoke but I'm wondering if there is anything I should be checking before replacing the yoke?