AMC 20 solid axle leaky seal - JeepForum.com
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post #1 of 7 Old 03-17-2020, 02:55 AM Thread Starter
MomoJeep
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AMC 20 solid axle leaky seal

I have the Moser 1pc axles and the seal leaks. A shop said the retainer or backing plate was warped. They said the "did their best" to flatten in, but now it leaks again. How does this happen?

I've also heard some 1-pc axle kits require proper shimming and this could be the reason?

Anyone know how to make the seal stop leaking?

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post #2 of 7 Old 03-17-2020, 07:44 AM
John Strenk
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Yes, they need proper shimming and sometimes there is a center block in the differential that has to be removed in order for the axle to go in all the way.

Typical instructions:

https://www.morris4x4center.com/pdf/8586k.pdf

https://static.summitracing.com/glob.../MGR-amc20.pdf

https://ocd4wd.com/2017/09/11/amc20-1piece-swap/

If they just threw the parts in without taking measurements it could be sitting out too far warping your backing plate causing leaks.
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post #3 of 7 Old 03-18-2020, 04:16 PM Thread Starter
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I guess I should add that I drove it for years without a leak. But when the shop took it apart they found a warped seal-plate. I'm confused how it can work fine fir many years and then one day it is leaking and warped?
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post #4 of 7 Old 03-19-2020, 10:23 AM
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Quote:
Originally Posted by MomoJeep View Post
I guess I should add that I drove it for years without a leak. But when the shop took it apart they found a warped seal-plate. I'm confused how it can work fine fir many years and then one day it is leaking and warped?
Yeah that's a mystery. The outer end of the axle actually requires RTV between the backing plate and housing flange, then the outer seal sits against the backing plate and requires RTV to seal the seal plate against the backing plate so if the backing plate gets warped you actually have two surfaces that may leak. If the warp is just slight, perhaps a machinist can take a slight cut off the side that seals the housing flange side then use a thick gasket with RTV to seal the outer seal. Just a thought.Probably the best thing is to locate another backing plate.
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post #5 of 7 Old 03-19-2020, 05:05 PM
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Ive always had problems with getting a good seal at the backing plate where 80cj described, due to the oil and grease and not being able to really get in there. The trick for me was always a complete tear down, cleaning, new seals, and silicone the seal plate to the backing plate, the day before assembly.
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post #6 of 7 Old 03-20-2020, 06:06 PM Thread Starter
MomoJeep
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A user named "Windknot" posted on this some years ago..

If when you reassembled the backing plate to the axle flange and didn't make ABSOLUTELY sure the surfaces were spotlessly clean from grease/oil and completely flat, the silicone adhesive will NOT seal.

Putting the assembly back together all at once almost requires two men and a boy. Since I'm usually in no hurry I do it in two steps with time for the silicone to set up between steps.

Here's how I do it:

Step one is cleaning everything and making absolutely sure the mating surface of the backing plate is absolutely flat. Then I attach the outside seal to the backing plate and use the bolts to hold it together while the silicone sets up. I then call it a day and find myself an adult beverage worthy of consumption.

The next day after it's set up, I back the bolts out and then mount the assembly to the flange. This way I'm not fighting slipping an axle in while trying to keep all the silicone goo out of where it doesn't belong. Everything is MUCH easier with the only wet silicone on the axle flange. This way there aren't too many moving parts.
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post #7 of 7 Old 03-20-2020, 08:48 PM
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I do believe thats where I learned it from.
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