M38 Rear Main Oil Seal ?

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M38 Rear Main Oil Seal ?

Post by Rod » Sat Jul 04, 2020 1:29 pm

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.
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Re: M38 Rear Main Oil Seal ?

Post by dpcd67 » Sun Nov 01, 2020 4:56 pm

The ones you get from Ron Fitzpatrick Jeep parts; (the guy who is paying for you to have this great site) NOT ones you get from those other vendors. Those are the only parts I use.
HOWEVER! If all your machine shop was turn the crank at the RMS area, then you will never get it to stop leaking; that area can't be turned; it must be welded up first.
I just had one done, by Abrahams; welded and then turned. That area is not like the bearing journals.
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