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Author Topic: Rear main seal questions  (Read 570 times)

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Offline aboyandhisdog

Rear main seal questions
« on: March 31, 2020, 09:09:59 PM »
I need to R&R my rear main with the engine in the jeep.  The universal manual says no problem, but doesn't really go into how to do it.  I have watched what You Tube videos I can find, but I have not found any where it is done with the engine in the jeep.  Metalshaper has good videos but the engine is always on a stand.

So....my questions:  How hard a job is this for a "shade tree mechanic" at best?  Can I do it using just ramps or no ramps at all?  Does anybody know if there is a good video, manual, or thread written up about just how to do this?  And, last but not least...what seal do you all like?  I have read that the Best brand rear main seals are no good, the Fel-Pro seals are no good, and the rope seals are sometimes good.  Most of the opinions are from Metalshaper, and I see where he is coming from, but am a bit confused as to what options are out there given that he seems to hate everything. 

Any thoughts on this?

Thank you!
Tom


Offline zhandyside

Re: Rear main seal questions
« Reply #1 on: April 01, 2020, 11:39:57 AM »
I've changed a few rear main seals on L134's and many other engines with a two piece design. Doing it in frame isn't too bad. It helps to loosen the other main bearing caps to allow the crank to drop a little bit to make the top half removal and installation easier. Just be sure to re-torque the bearing caps when you're done.

I used a "Best Gasket" seal on my most recent L134 job (seal purchased in Nov 2018) and it hasn't leaked for me so far. It's possible that maybe their quality standards have gone down with newer production?
1951 CJ3A - Restomod in progress

Offline BillT

Re: Rear main seal questions
« Reply #2 on: April 01, 2020, 11:58:08 AM »
Tom I certainly am no expert on this subject but I am willing to share my dismal experience with the rear main seal.

Mine was leaking, a number of drops overnight, when I purchased the jeep nearly three years ago. It was needing an engine overhaul but the fun-money account wasn't there yet. I wasted good money on seal renew concoctions. So I, like you have done, started studying up on the subject.

I decided to do the in-place replacement. So I jacked up the front end, dropped the oil pan, removed the lower bearing housing, and loosened the middle main bearing a bit. The engine had the old style seal, the seal had a shoulder the laid over the housing edge. I used a piece of heavy copper wire to push the upper half of the seal out of its groove. Cleaned things up. The replacement seal was the Best gasket. Installed it, using a small amount of sealant where recommended. Put it all back together, started it up, and it poured.

To not bore you with all the details, the Best gasket was deemed defective and was replaced with the same results. With the upper half of the Best gasket in place , the lip on one side was tight on the crank surface but the other side was loose on the crank. I hoped when the lower bearing half was installed compression would correct this situation. But no luck.

 I shoved an oil absorber mat between the oil pan and bell housing and lived with the 'tampon' for a while. I did try a Crown seal but it was a poor fit, too loose in the grove. I tried a Omnix seal but could not get the upper half to slid thru the groove. So I went back to the 'tampon' until this past January when I rebuilt the engine.

With the engine on the stand the first thing inspected was the seal. Nothing looked out of the ordinary, the crankshaft was polished. My buddy helping had used a seal he got from Summit Racing on his f-head and had good luck with it. So I tried that one, I think it's an Omnix, it has the shoulder that fits over the edge of housing like the original seal, and with 140 miles on it so far no drips.

I know some here have had problems with the Omnix brand seals but, for me, it's working for now. Best, no pun intended, of luck with your repair.

Bill
'52 CJ3A, early M38A1, '70 Commando
25' travel trailer, Lance 855S truck camper
Love to camp

Offline zhandyside

Re: Rear main seal questions
« Reply #3 on: April 01, 2020, 12:57:03 PM »
Looking at metalshaper's latest video about rear main seals, it seems the issue with the 'Best" seal is the seal is too large. His fix on rebuilds it to have the seal surface welded and reground to a slightly larger size. I wonder if the same effect can be had on an in frame repair by trimming an small amount from both sides of the seal with sharp razor?
1951 CJ3A - Restomod in progress

Offline athawk11

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Re: Rear main seal questions
« Reply #4 on: April 01, 2020, 01:50:07 PM »
I hate to admit how much experience I have with rear main seals on these engines.
 
My current rule of thumb is...If the engine and crank are newer than an M38 engine (based on casting and serial number) then I would install the best version of the rubber seal, if the seal surface on the crank is in very good condition.

If it is an older version of the L-134, I will use the rope seal.

Engine in place swaps...

Pulling a rope seal in with a Sneaky Pete or any other method is a complete waste of time.  Pull the engine.

Setting the rubber seal can be done effectively as described by the other gentlemen in this thread.
« Last Edit: April 02, 2020, 08:33:50 PM by athawk11 »
2-1949 CJ3As
1-1946 CJ2A

Offline aboyandhisdog

Re: Rear main seal questions
« Reply #5 on: April 02, 2020, 03:38:09 PM »
Looking at metalshaper's latest video about rear main seals, it seems the issue with the 'Best" seal is the seal is too large. His fix on rebuilds it to have the seal surface welded and reground to a slightly larger size. I wonder if the same effect can be had on an in frame repair by trimming an small amount from both sides of the seal with sharp razor?

You know, this is exactly what I was thinking as I watched that video and thought I would ask him that in the comments.  Well, a couple of others beat me to it.  His reply was that you can't do that.  I fail to see why, exactly.  I mean trimming it isn't going to change the radius of the seal.  Thing is, Brian knows a hell of a lot more than I do and if he thinks it can't be done, well...
Tom


Offline zhandyside

Re: Rear main seal questions
« Reply #6 on: April 02, 2020, 04:04:56 PM »
You know, this is exactly what I was thinking as I watched that video and thought I would ask him that in the comments.  Well, a couple of others beat me to it.  His reply was that you can't do that.  I fail to see why, exactly.  I mean trimming it isn't going to change the radius of the seal.  Thing is, Brian knows a hell of a lot more than I do and if he thinks it can't be done, well...

I know a lot of work would be involved, but I still think it would be worth a try. I know some modern 2 piece rear main seals have a metal ring embedded into the outer portion to keep the seals shape, but I can't recall the how the Best brand one was made. My guess is the amount of material that would need to be trimmed would have to be exact, which would be hard to do. It would also require a bit of math to determine exactly how much would need to be removed.

Our 3A hasn't been on the road since the seal was installed, but it has probably 20-30 of engine run time without any leaks. So I'm keeping my fingers crossed. My guess is the amount of material that would need to be trimmed would have to be exact, which would be hard to do.
1951 CJ3A - Restomod in progress

Offline aboyandhisdog

Re: Rear main seal questions
« Reply #7 on: April 02, 2020, 05:44:35 PM »
I just ordered one on Ebay which looks like the same one that Kaiser Willys sells.  Maybe an Omix???   BillT mentioned having good luck (so far) with the Omix so it's worth a shot.  Anyway, it does say it's "new and improved" so what could possibly go wrong?
Tom


Offline Bob W

Re: Rear main seal questions
« Reply #8 on: April 02, 2020, 08:18:10 PM »
It seems that up until about the early 50's there was quite a bit of variation in the size of the crankshaft rear sealing surface diameter, and perhaps also the grove in the block. With a rope seal it really didn't matter because the rope compressed to fit the area and the excess was cut off. Then came the military waterproof engines with stricter tolerances and rubber rear main seals. Then gradually the civilian engines caught up and also used rubber seals. Fast forward to now. There is the possibility of having a crankshaft and/or block combination that isn't good for a rubber seal. And then there were rubber seals that were not made correctly. All this adds up to potential problems, rubber seals too loose, just right and too tight. Too loose and they leak. Just right is good. If the seal ends up being too tight the crankshaft and rear bearing will probably be damaged by the excessive heat buildup and sometimes it locks up the engine. It is easy to tell if the seal is too tight when the connecting rods are not installed. The crankshaft should turn easily with only slight force. If a lever is required to rotate the crankshaft there is a problem.
Bob W

Offline 64CJ5

Re: Rear main seal questions
« Reply #9 on: April 03, 2020, 11:36:41 AM »
Morning Tom,  When the shop rebuilt the F-head for my '64 they put in the rope seal.
Some time later the oil started running out the rear.  I dropped the pan and found pieces of rope seal in there.  Had to drop the oil screen to clean it as it was nearly plugged with rope seal.  I backed the crank shaft cap bolts out a little and worked in a new rubber seal.  Buttoned every thing up and so far so good, no leaks.  It has been a couple of years now.  Good luck with yours.
Stay safe,   Till we Jeep again!   Tom
The sun never sets on the mighty Jeep.

Offline aboyandhisdog

Re: Rear main seal questions
« Reply #10 on: April 03, 2020, 11:51:18 AM »
That is encouraging, Tom.  You don't happen to remember the brand of seal do you? 

That is very interesting, Bob!  I'd not have thought that there would be a consequential difference in the diameter of the crankshafts, but it does make sense and explains part of the problems that guys are having.  I'm thinking of buying two or three different brands of seal and seeing which one looks like the best fit.  Trial and error science at it's worst here! 

See you guys in Sept. (maybe)!
Tom


Offline 64CJ5

Re: Rear main seal questions
« Reply #11 on: April 03, 2020, 08:30:31 PM »
Sorry Tom I do not remember the brand or where I got it.

Take care,   Tom
The sun never sets on the mighty Jeep.

Offline TX

Re: Rear main seal questions
« Reply #12 on: April 10, 2020, 03:01:54 PM »
My machinist recommended a company in California that makes seals for vintage vehicles.  EGGE machine Co.  url = egge.com ph (562) 945-3419.  The gasket i got ( BST3B71) looked like the new double seal you see in new type wheel bearing seals. They may have a suggestions on how to replace the seal.
I have only got  150 miles on the engine but so far it  works.
Good luck
Projects are like life itself, its the journey that makes the trip not the arriving.

Offline aboyandhisdog

Re: Rear main seal questions
« Reply #13 on: April 10, 2020, 10:23:42 PM »
That is good to know Tx.  That is a Best brand seal and I'm glad to know you are having good luck with it.  Some say they are too big, but maybe they have refined production a bit.  I am looking into ordering one.  Thank you!
Tom


Offline TX

Re: Rear main seal questions
« Reply #14 on: April 11, 2020, 12:30:49 PM »
As I remember, it was expensive, but that was one job  I didn't want to do twice.  ;D

How is your  clutch?  Whenever I had the main seal go bad in other cars oil ruined the clutch disc.  I have never had on go out on a 134.
Projects are like life itself, its the journey that makes the trip not the arriving.