Rear-end seal?

Grump hit the nail on the head. The nut's a bugger to get off and on cause it's torqued to 240 ft. lbs. and a groove in the yoke is probably what is causing the leak. I rebuild a 8-3/4 for my car last summer and it wasn't leaking before I rebuilt it but it does now and I'm sure I got the seal in right. I remember the yoke having a little groove where the seal rode but thought since it didn't leak before it shouldn't with a new seal. WRONG!!