I had a leak one time because of pitting on the sealing surface. For that case my surface just outside of the seal area was not pitted, so I had success by installing the new seal not all the way in to let the seal ride on that clean outer area.
1950 GMC 100 Panel Truck, 1958 270, 3-spd Saginaw with BW OD, 3.73 12 Bolt Differential from a 1966 C10, Front Disc Brakes Bought it in pieces 9-1976, driving since 6-1978 Follow in the DITY | 
