Rear main seals are subject to leakage for many reasons, and have been problematic especially since asbestos has been banned as the primary material. The seal groove was not designed for a lip seal and likely is not concentric with the rear main bearing, thus virtually guaranteeing leakage. The following are important elements in obtaining a good leak free installation.
∙ Crankshaft rear main seal surface should be ground perfect and polished like a rod journal without ‘lead’. This is mandatory
∙ Seal should be OEM asbestos material (from the 50/60’s)
∙ Install with ‘half round’ per shop manual.
∙ In vehicle installation is a guaranteed non-success.
∙ Machining and installation of a one piece rear main seal is probably the best (but expensive)alternative to an asbestos (original equipment) ‘rope’ seal.
Edited 1/28/14 del