rear main seal info

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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artificer
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Re: rear main seal info

Post by artificer » Tue Jul 30, 2019 2:13 pm

Anyone having the picture I drew [& can't find now] indicating what offsetting the seal is, please PM me & I will re-post. But here is an even better presentation! https://www.youtube.com/watch?v=WSy5hywk_ls
Here is a picture of the sneaky pete:
Image
New thread on General Knowledge forum & info on obtaining the Best Gasket seal from Ron....
viewtopic.php?f=4&t=309029
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.


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Re: rear main seal info

Post by Adam » Mon Oct 28, 2019 8:44 pm

I wonder if this is what it looks like if a new main seal is no good. Not my project, or build, Turned over pretty hard, This is the result after running for the second group of 2 minutes. Oil in engine was nice and clean when first started, now ugly and black dripping out rear seal.

Adam
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Re: rear main seal info

Post by AmphibAndy » Tue Feb 23, 2021 11:27 pm

I am sticking with the rope seal, I have built rope seals into Flat Head V8s, and Jaguar XK engines and Willys a long while back, all being fine if you take your time. I always soak the oil seal at least overnight in oil. My machine shop tell me the they will need to take off about 20 thou of the seal track on the crank to clean up the rusted/pitted surface there. I personally cannot see any reason why the traditional rope seal should not take up that reduced diameter, but if anyone thinks I will have a problem please let me know. I cannot see any alternative to be fair. thanks

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Re: rear main seal info

Post by Jezzos » Mon Aug 02, 2021 5:50 am

AmphibAndy wrote:
Tue Feb 23, 2021 11:27 pm
I am sticking with the rope seal, I have built rope seals into Flat Head V8s, and Jaguar XK engines and Willys a long while back, all being fine if you take your time. I always soak the oil seal at least overnight in oil. My machine shop tell me the they will need to take off about 20 thou of the seal track on the crank to clean up the rusted/pitted surface there. I personally cannot see any reason why the traditional rope seal should not take up that reduced diameter, but if anyone thinks I will have a problem please let me know. I cannot see any alternative to be fair. thanks
I believe it will be a success.

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Re: rear main seal info

Post by Ladislav » Fri Sep 22, 2023 8:02 am

What is the correct number from Best gasket? The Payen one didn’t last for a long time, after one year running the gaskets, turn for 90• it and didn’t work anymore. The Payen ones are too tight.

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Re: rear main seal info

Post by YLG80 » Sat Sep 23, 2023 1:57 am

Ladislav wrote:
Fri Sep 22, 2023 8:02 am
What is the correct number from Best gasket? The Payen one didn’t last for a long time, after one year running the gaskets, turn for 90• it and didn’t work anymore. The Payen ones are too tight.
Hi Lad,
The (working) rear main seal number from Best Gasket is 3B71 ( download/file.php?id=194795&mode=view)
https://www.carid.com/best-gasket/rear- ... -3b71.html

You have an eleven pages discussion about that subject, with dimensions and drawings, good and bad seals, here :
viewtopic.php?p=1890625#p1890625

Greetings
Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
serial 164794

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Re: rear main seal info

Post by Ladislav » Sat Sep 23, 2023 7:48 am

Thanks Yves. 👍

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Re: rear main seal info

Post by CFP » Mon Jan 29, 2024 9:45 am

I wasn't sure where to post this question, but this looked like a related thread.

I've just completed my first jeep, a 1942 Willys MB with engine block number MB103546. I've put 250 miles on it so far going about 7 to 8 miles each time I take it out. That's a little over 30 trips. Each time I get home, I get about a 2" diameter drip of oil on the concrete that seems to be running down from the rear main seal. The back of the oil pan is dry. The engine block plate to bell housing has the oil coming down. It doesn't seem to be coming out of the hole in the bottom of the bell housing. It looks like it's being blown across the skid plate, so it's shiny from oil too. It's not enough oil that the concrete stays wet. It's also not enough oil that the oil level on the dipstick has gone down to show I need to add more oil. I'm posting a picture to see if that helps. Some of the oil at the back of the skid plate if from the transfer case, but it hasn't dripped enough to mark the concrete yet. I was able to fix all other leaks including changing to a newer style oil pan after the riveted F marked one that came with it almost poured oil out from around the rivets.

I kept hearing you can't make these leak free, but do I count myself lucky that this is all the oil that's leaking, or should I consider going back in to redo the rear main seal?
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Re: rear main seal info

Post by tamnalan » Mon Jan 29, 2024 11:28 am

That little grooved recess in the crankshaft where the seal rides, behind the last bearing journal, sometimes gets some pits. It's not easy for the typical machine shop to resurface that groove, I'm told. It might be the culprit. What sort of seal did you use?
Alan W. Johnson
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Re: rear main seal info

Post by CFP » Mon Jan 29, 2024 12:57 pm

The crank shaft looked really good there. Maybe just a few pits there. The machine shop said they got the most out they could without having to talk about welding to build it back up. The most pitting on the crank seemed to fall in the oil groove portion of the rear bearing. I probably should have taken more pictures as I reassembled everything.

I went with the Best Gasket neoprene seal. I started with a rope gasket from Felpro. I pressed the rope down into the groove of the cap and case as good as I could, but it still stood out about 3/16". I pulled it out to see that it had formed all the way to the bottom of the groove. When I put the crank in with no seal, it looked like about 1/16" clearance between the crank surface and case. I've read on the boards here that rope one could bind with that much sticking out. Before putting in the neoprene one, I tightened the crank bearing caps with no connecting rods to make sure everything turned easily and then did it again with the rear seal to make sure it wasn't binding before installing pistons and rods.

When I start the engine and let it run in the driveway, I don't get a leak. It's almost like it leaks just a bit when I shut it off after a run that gets it up to full operating temperature. Now approaching 300 miles and it still doesn't show low oil on the dipstick and oil pressure runs 30-35 lbs. My main concern would be if this starts getting the clutch disk oily. As this is my first jeep, I'm not sure if this is sort of normal, or if I should be able to get this leak free.

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Re: rear main seal info

Post by tamnalan » Mon Jan 29, 2024 5:44 pm

Don't you just love this hobby!! :)

My MB has piddled plenty of oil out of that bell housing weephole, but in my case it was from an oil migration problem in the transmission. My clutch still works fine.

My $0.02... if you're more into wrenching on it than driving it (and many of us are!) then pull your motor and check that seal out. Perhaps the crank's seal journal was already ground sometime back and is now undersize. Maybe it's pits. Maybe the leak is in those rubber dowels that help seal the bearing cap. Otherwise, drive it and hope it doesn't get worse or affect the clutch. It may not.

Some clever guys have done good crank oil seal repairs with the engine in the jeep. I'm not one of those guys.
Alan W. Johnson
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Re: rear main seal info

Post by tamnalan » Mon Jan 29, 2024 5:58 pm

I just looked at your picture more carefully. Are you SURE it isn't transmission oil? Catch some in a cup.

An overfull trans can puke out the front.
Alan W. Johnson
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Re: rear main seal info

Post by CFP » Tue Jan 30, 2024 4:03 am

I hadn't thought about the trans. I'll catch some and let you know. I like wrenching, but really don't want to pull the engine back out unless there's no other option. Thanks

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Re: rear main seal info

Post by CFP » Wed Jan 31, 2024 6:37 am

Alan,
It was transmission gear oil. I let it settle and removed the fill plug and it started draining oil. When it got down level with the bottom of the fill hole, I put the plug back in and took it for a drive. NO LEAK! Can't thank you enough. I really didn't want to pull the engine and couldn't imagine doing a good job on a main seal repair with it still in the jeep. I don't know how I got the oil above the hole to begin with, but now I know to watch that more closely.
Thanks,
Charles

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Re: rear main seal info

Post by tamnalan » Wed Jan 31, 2024 7:33 am

:) . I can't count all the times I've been helped by others in this forum! Glad to return the favor.
Alan W. Johnson
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