HELP! Tranny won't stop leaking!!!!

[rel3rd]

In my new toy, a 94 GT, I have a stock T-5 transmission. When I got the car, with it came a brand new FRPP aluminum driveshaft. I installed it, and within a few days noticed a small spot on the driveway where I was leaking some tranny fluid. I replaced the seal, which is a "cut and dry" repair, nothing difficult. It still leaks. An old timer at work says I can take the shaft out (again), and use some crocus cloth and "sand" the yoke a little and this will help it seal??? He said it (the outer part of the yoke)is actually too smooth and that's why it won't seal??

Anyone ever had this problem? How'd you fix it??

BTW, the stock driveshaft did NOT leak...

Thanks, BOB