1pc AMC20 Axle seal leaks

MomoJeep

Basic User
CJ-8.com Member
City
Seattle
State
WA
#1
I have the Moser 1pc axles and the seal leaks. A shop said the retainer plate (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?
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Biloxi
State
MS
#2
Just a wild guess, but I imagine the shop drove in the inner bearing stops without checking bearing "stick out" before pressing the bearings on the axles.

You have to install the inner metal stops first, then dry fit the bearing, see how far the bearing sticks out the end of the axle housing. If the bearing sticks out too far, you are supposed to remove the inner bearing stop piece, and machine it down to obtain the correct bearing stick out.

If you don't do this, and the bearing sticks out too far, when you slide the axle in and bolt the brake backing plate/axle seal plate down, they will "bow", and leak.

I personally think the "bearing stick out" they call for is a little much. You want a little "stick out" to put a bit of pre-load on the bearings. But, to much stick out will cause bent brake backing plates :shrug:

If the "stick out" isn't an obscene amount, I always though that maybe you could install some original two piece axle shims between the axle tube end and the brake backing plate to get the correct/less "stick out". This would be easier then machining down the bearing stop parts that are drove into the axle tube ends :shrug:
 

MomoJeep

Basic User
CJ-8.com Member
City
Seattle
State
WA
#3
WOW! I am going to admit to making a dumbass mistake. Now, I'm no dummy, after all I did build the entire Jeep from the frame up! But get this... When I ground down the bearing spacers to try to get the right amount of "stick-out", I ground the backside (facing the diff) of the spacers. I must have assumed after doing a dry-fit and measuring and grinding down, that it was then ready for assembly and not double-checked, because grinding down the "backside" of the spacers MAKES NO DIFFERENCE! It's the lip on the front side (facing wheels) that sits between the inner axle tube shoulder and the bearing. This is the side that must be ground/machined down in order to reduce stick-out!!

I must have been driving it around with about 0.100" stickout (they say it should be 0.020-0.080). It worked fine for a number of years before I started bouncing around on rocks... I think the excessive stick-out combined with lateral loading while wheeling must've caused the seal-plate to eventually warp and fail.

I'm shocked to discover this today. It's been about 10 years since I first put it together (and apparently did it wrong)!
 

Belizeit

CJ-8 Member
CJ-8.com Member
City
River Ridge
State
La
#6
About 5 years ago a bought seals and bearings because somewhere in the future it will probably be opened up. Very small seep on right side, but not enough to bother me to replace or look yet thats for sure.
 

MomoJeep

Basic User
CJ-8.com Member
City
Seattle
State
WA
#7
OK, I just learned something I didn't figure out 10 years ago. This may be helpful to others. The Spacer Rings are designed to butt up against the inner seal. Then the bearing rides on the rings. HOWEVER not all AMC 20's were built the same. On mine, the bore for the diameter of the bearing only goes in a little further than the width of the bearing itself. Then it narrows down a bit, and therefore there is a shoulder inside the axle tube. The wider lip of the spacer ring stops when it hits the shoulder. (I didn't know any better, and I thought that was how it was supposed to be, by design). Therefore if I was to grind the side of the spacer ring facing the inner seal beyond the point of contacting the seal, it wouldn't make any difference. The seal would no longer be supporting the spacer ring, because it's hung up on the shoulder anyway. Turns out most AMC20's were bored deeper (the bearing diameter) so these spacer rings would NOT stop on this shoulder inside the tube, and would rest on the seal. Glad this got figured out.
 

CJ7Pilot

18436572
LIFETIME
CJ-8.com Member
City
Yuba City
State
CA
#8
Here's a good instruction link: https://ocd4wd.com/2017/09/11/amc20-1piece-swap/

The spacer rings should not butt up against the seals, those seals are not designed that way. Also, all AMC 20s should have the same shoulder depth, because the original wheel bearing races sat against that shoulder. The one-piece axle bearing spacer is designed to butt up against the machined shoulder, so you can adjust the "stick-out" of the new set 9 bearing.

Occasionally, the original bearings will seize up, and spin in the bore (that happened to mine, at some point), and that makes it just about impossible to fit any kind of new bearing. Fortunately, I found a Warn full-float axle kit, which eliminates that style of bearing altogether. ;)
 

MomoJeep

Basic User
CJ-8.com Member
City
Seattle
State
WA
#9
This is where I get frustrated. These kits have been around for a very long time, yet there is still conflicting information! You'd think it'd be all cleared up by now! I talked to Mosier Tech help on the phone yesterday, and the guy said you DO rely on the seal, and that there shouldn't be a shoulder that stops the spacer ring. And in this video (at 4:43) they show grinding the narrower side of the spacer which contacts the seal.

I've read that not all AMC20's are bored out the same way. My only conclusion is that you may have to grind EITHER or maybe both sides of the spacer ring to make it work. (?) Thoughts?
 

MomoJeep

Basic User
CJ-8.com Member
City
Seattle
State
WA
#11
For putting together the backing plate and outer seal retainer plate, anyone recommend a sealant better than just RTV?
 

CJ7Pilot

18436572
LIFETIME
CJ-8.com Member
City
Yuba City
State
CA
#12
My only conclusion is that you may have to grind EITHER or maybe both sides of the spacer ring to make it work....
That sounds like a good approach; treat every axle as a custom install, and do what you need to do to make it fit properly. :thumbsup:
 
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