Maybe I am missing something here but the way I understood your first post, is that you have lowered the transmission and fluid is coming out of the rear seal area? If you don't have an annular plug to put over the output shaft to seal it while it is in the lowered position, it's gonna leak. You can either drain the fluid while it's down, or remove the slip yoke from the driveshaft and use it to "plug" the output shaft.
If I misuderstood and it is simply leaking as others are repsonding to, the only way to fix it is replace the rear seal. No amount of polishing the barrel of the yoke is going to stop a leaky seal.
Richard
Tech Support
Tremec TKO, T45 & T56 Transmission Systems
__________________
Self Proclaimed "Resident Manual
Tranny/Driveline Guru"
Go with PI heads and quit watching The Fast and the Furious.
(thanks 2 IhaveadopeGT)
Remember, it is almost impossible for anyone, myself included, to diagnose a problem over the internet without seeing the car. My advice is simply that, advice based on years of experience. I don't want you or anyone taking my word as gospel. I am trying to give some direction as to what I think may be happening.
Transmission seal 
