Chrysler, Dodge Rear Main Seal Info
Chrysler, Dodge, DeSoto and Plymouth 6 engines used 3 different rear main seals depending upon the engine year from the 1930s into the 1960s.
Best Gasket makes the Best 4162 rope seal set for use with the factory 3 bolt steel retainers priced at $18.00, Best 4164 Steel 3 bolt plate with rubber lip seal set priced at $37.00 and the Best 3675 internal 2 piece rubber seal set that fits on a square ledge inside the block without the oil slinger on the crankshaft priced at $61.00
The following information list is what I have put together from the listings from the 1955 Victor Master Gasket catalog concerning passenger car engines. The truck engines vary widely on what main seal was used depending upon application.
Chrysler and DeSoto 6 engines- 1937-Early 40 engines used the Best 4162 seal set. Late 1940-47 engines used the Best 4164 seal set. 1948-54 engines used the Best 3675 seal set.
Dodge 6 engines- 1933-42 Early engines used the Best 4162 seal set. Late 1942 -Early 51 engines used the Best 4164 seal set. Late 1951-59 engines used the Best 3675 seal set.
Plymouth 6 engines- 1933-52 used the Best 4162 seal set. 1953-59 engines used the Best 3675 seal set.
The Best 4164 seal set can be used to replace the original rope seal and retainers on most of the earlier engines if the crankshaft seal journal (2.650 in) is the correct size to match the 4164 seal. This was a common practice to do this. Some engines that were made for the Best 4164 seal set can use the Best 3675 seal set if the crankshaft does not have the cast in oil slinger and if the square ledge in the engine block and cap is correctly machined to accept the Best 3675 seal. Most engines that were made to use the Best 3675 seal may still have the bolt holes in the engine block and main bearing cap for the seal retainer. These may or may not be threaded. I had one customer who ground the oil slinger off the crankshaft in an earlier block that used a rope seal and installed the Best 3675 seal set and it didn’t leak. It all depends upon the engine design and the machining quality in the rear main seal area on what can be used.
Below are picture of the rear main seal sets:
