Joined: Apr 19, 2005 Posts: 15 Location: Heart of Dixie
Posted: Sat Jul 04, 2020 3:27 pm Post subject: M38 Rear Main Oil Seal
I asked this question over on the M38 boards on the G boards but I figured I would ask it here to get the most valuable response.
I recently installed an engine that I had built about 12 years ago in an M38. This engine had only about 10 miles on it since rebuild and ran like a top. I pre-lubed (oil pump with teeth ground off) the engine before I cranked it. The engine seized up after just a few miles. Suspecting the rear main oil seal, I pulled the engine and removed the crankshaft, I noticed the rear mail oil seal was the dreaded Victor oil seal. Took the crankshaft to the our local machine shop and had it turned.
I ordered a new oil seal from one of the Military parts dealer in the Midwest. The oil seal that they sent was a "Best Gasket 3B71" and they said I shouldn't have a problem with the oil seal causing another crankshaft seizing problem. Well, I installed the oil seal according to the M38 & M38A1 books, buttoned the engine back up and installed it in the jeep. I ran the jeep for about 6 miles and pulled the jeep back into the shop and noticed that I now have a small oil puddle under the jeep. Apparently the new rear main oil seal is leaking. I am going to pull the engine back out and put another oil seal in.
What brand of rear main oil seal should I use? Please don't say that you would 40 year NOS seals, cause not everyone has access to a NOS supply.
Not wanting too but I'm thinking of going old school and installing a rope seal.
If you were rebuilding an M38 engine now, what oil seal would you use? Comments welcomed & appreciated.
The rope seal Was meant for the sizing of the early crankshaft and the preformed seal was meant for the sizing of the late crankshaft. Willys published a service bulletin on this issue over a half century ago. The AERA publish another on the topic in 2002. So first make sure you have chosen the correct type of seal. Then shop for opinions on the best available brands.
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