If you're having trouble with rear axle seals in a Ford 9", Currie has something that should help. They sell a large diameter sealed axle bearing that has an O-ring in the outer race. Since the bearing is sealed, and is pressed on the axle, the O-ring takes the place of the axle seal, and is more reliable.

I had to go this way because the supplier of my rear axle (Yep . . . Gibbon) hosed up the seal seating area when they narrowed the rear end.) However, the bearing seating area is fine. It's not cheap, but it you need it, you need it.

http://www.currieenterprises.com/ces...E.aspx?id=1452