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Moser 12 bolt axle seal issues?

This is a discussion on Moser 12 bolt axle seal issues? within the Drivetrain forums, part of the LSx Technical Help Section category; I know of at least two other members that have had issues with the axle seals in their Moser rears. ...

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    Moser 12 bolt axle seal issues?

    I know of at least two other members that have had issues with the axle seals in their Moser rears. I replaced the passenger side seal last year in August and discovered (thanks to Zap's keen eye) that it is leaking again already.





    Upon removing the axle, I really couldn't find any apparent issues. The seal looked good, was installed square in the axle tube, I had used a thin coat of gasket sealer around the circumference of the tube, and the seal and axle were given a light coat of gear oil prior to installation. The surface of the axle where the seal rides has no imperfections or burrs (checked by both sight and feel).





    I pulled the existing seal out with an axle bearing puller and, other than the indentation made by the puller, I couldn't find a problem. I cleaned everything and wiped it down with brake cleaner.





    Measurements were then taken from the lip against which the bearing seats and compared to the axle. I elected to not quite seat the new seal as deep in the axle tube (there is a lip that it sets up against) and used a seal installer to ensure that it was not distorted. I also measured after the seal was installed to again make sure that it was square in the tube. Time will tell if the issue becomes a three-peat like Jon's. Thoughts?

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    Moderator 35th-ANV-SS's Avatar
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    Good luck, Jeff. The person that installed my 2nd seal installed it backwards. Upon installing the 3rd one myself, I slightly crushed the seal and within a week it was leaking bad. I then pulled that one and installed a 4th one using an axle seal install tool I made. I machined a washer that was about .005" smaller in diameter than the ID of the axle tube. I did this so the entire surface of the seal was being driven into the axle housing straight. Once I had the seal fully seated, I used a generous amount of RTV around the OD of the seal to the ID of the housing. I also, like you, oiled the axle prior to sliding the seal over it. It's been around 1.5 years now since that install without issue. The driver side seal never has leaked, thankfully.
    It's on jackstands.

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    Moderator Firebirdjones's Avatar
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    Is Moser still making the c-clip eliminator axles this way with just a single seal way up inside the housing? I would have thought they had gotten away from this design by now.


    Strange uses a seal way up inside the housing as well but it's not necessary on their design, they make their C-clip eliminator axles with another seal out at the bearing retainer to keep the oil where it belongs.

    When I had issues with leaking Moser axles about 10 years ago it was the same setup Jeff. Their explanation to me about their C-clip eliminator axles was that they were primarily designed for drag racing where cars only go in a straight line. They weren't meant for street driving where cars are constantly turning and sloshing the oil from side to side.
    When I mentioned drag cars turn too, they turn on the return road, they turn into the water box, they turn in the pits etc....I got no real response. So those axles went back. I'm actually a little shocked they still make them that way.

    I've been with Strange ever since. They have a superior design when it comes to the bearings seals. I can dig up some pictures if you want to see the differences. Hopefully I have some of the bearing seals because when I took those pictures, the seals weren't my main focus.

    Anyway, I hate to say this, you might get a couple years out of that seal scenario with Moser but eventually they do leak again. Depends on how much you drive it.
    The real perminant fix is to go with Strange's bearing and seal/retainer setup so you don't have to keep fooling with it.

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    Moderator Firebirdjones's Avatar
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    This might give you an idea Jeff. I fished around and found a couple of pictures.

    This is the Strange bearing setup. Those gold cad plated looking seals are the extra seals held into place with the bearing retainer plate.



    Here is the Strange axle before I started assembly. I'm showing this because if the Moser axles aren't machined this way then they won't accept the Strange bearing setup. In which case you'll have to use their axles as well to cure the dreaded leak issue.



    And here is the axle going together. I have the reluctor ring pressed on (4 channel). That black ring pressed on is actually the seal surface for the extra outer seal Strange uses held with the bearing retainer. At this point in the assembly it's time to slide the backing plate on, then the bearing retainer, then the gold colored seals in the picture above, then press on the bearing and it's retainer ring. Meanwhile there is still the seal up inside the rearend housing too.


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    Member jonnyman's Avatar
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    having the seal replaced again next weekend, If it shits the bed again I will seriously consider going to a strange rear end setup. I don't really race it's more of a daily and a weekend show car.
    Quote Originally Posted by pajeff02 View Post
    I know of at least two other members that have had issues with the axle seals in their Moser rears. I replaced the passenger side seal last year in August and discovered (thanks to Zap's keen eye) that it is leaking again already.


    Click for full size


    Upon removing the axle, I really couldn't find any apparent issues. The seal looked good, was installed square in the axle tube, I had used a thin coat of gasket sealer around the circumference of the tube, and the seal and axle were given a light coat of gear oil prior to installation. The surface of the axle where the seal rides has no imperfections or burrs (checked by both sight and feel).


    Click for full size


    I pulled the existing seal out with an axle bearing puller and, other than the indentation made by the puller, I couldn't find a problem. I cleaned everything and wiped it down with brake cleaner.


    Click for full size


    Measurements were then taken from the lip against which the bearing seats and compared to the axle. I elected to not quite seat the new seal as deep in the axle tube (there is a lip that it sets up against) and used a seal installer to ensure that it was not distorted. I also measured after the seal was installed to again make sure that it was square in the tube. Time will tell if the issue becomes a three-peat like Jon's. Thoughts?

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    Thanks, FBJ! The sealing surface on the Moser axle is really short. I though about doubling up the seals, but I don't think there is enough space due to the position of the pressed bearing retainer ring. I think John may have mentioned it in my other post on this topic -- do I need to be concerned about the fact that gear oil made contact with my sealed axle bearing?

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    Moderator Firebirdjones's Avatar
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    I don't believe it will hurt anything.

    On the Strange setup, although it has an inner seal just like the Moser, I'd bet money that oil gets past that first seal after a while, just like you are seeing, I've had that issue myself. The only difference with Strange is the extra outboard seal between the bearing and retainer plate that catches it.

    The added feature of the Strange setup is the zerk or grease fitting that is at the top of the rearend housing just above each bearing. It pumps grease between the 2 seals for that bearing, even though it's a sealed bearing You wouldn't think it would be necessary but it's there.

    Every oil change I make an effort to pump 5-6 squirts of grease in each one. Now you would think since gear oil gets past that inside seal that possibly the grease would also get past that seal and into the rearend housing. Or maybe not, hard to say.

    Another tidbit, if you run one of those bearing support diff covers. You may have noticed the fill hole is WAY higher than stock. It's actually up above the center line of the axle tube. It fills these rearends too full if you bring the level up to the bottom of the plug. Oil that high would certainly work it's way past the inside axle seal eventually, and it also will blow oil out the vent too.

    The correct fill level actually has the oil level with the bottom of the axle tube a good 4" or so below that fill plug in the cover.

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    Spaz is My Mentor SMWS6TA's Avatar
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    Is this an issue for non c clip axles?

    My bearings for my 8.8 are different then what Jeff posted. My Moog had to be pressed on the axles.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by SMWS6TA View Post
    Is this an issue for non c clip axles?

    My bearings for my 8.8 are different then what Jeff posted. My Moog had to be pressed on the axles.
    Speaking of the aftermarket add on C-clip eliminator for OEM rears, it's the same issue. Depends on where you bought them from.

    If you bought the Moser C-clip eliminator then yes, I used that kit on a GM 12 bolt many years ago (10-12 years ago) and it leaked after about 6 months. That's why I'm surprised they still make it this way, even on their custom built aftermarket drop in rears, that just puzzles me. There is nothing in any of their literature that states it's not meant to be used on the street (at that time anyway), yet that's the explanation I got when I called about the issue. Yet they sell these drop in rears made in the same fassion. Crazy.

    If you bought the Strange C-clip eliminator, then it will be leak free. It's a slightly different design with a better seal.

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    Spaz is My Mentor SMWS6TA's Avatar
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    I have 9" housing ends welded on to the tubes and the axles are non c clip.

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    Moderator Firebirdjones's Avatar
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    9" housing ends are a good way to go. Do you have a picture of the bearing/seal setup?

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    I only fill it to the bottom of the plug on the differential. I noticed when I installed it that the cover plug is almost 2" higher than the differential plug.

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    Moderator Firebirdjones's Avatar
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    Yeah that fill plug is WAY too high. I've only seen one support cover with the fill plug in the correct location and that was the original when they first came out years ago. Now we have all these copies, and yes unfortunately I run one because at the time Strange was out of stock type covers so they sold me this one at a discount.

    Here is a picture of my wifes car with an arrow showing the fill plug on this support cover. It's way up above the center and actually runs parrallel with the top of the axle housing tube. If I filled that to the bottom of the plug it would have both axle tubes completely full of oil. There is no reason why they can't design these support covers with the fill hole in the correct location (which I will show in the next picture) As a matter of fact, they used to make them correctly.
    Unfortunately this Strange housing doesn't have the factory drilled and tapped plug up by the yoke like an OEM housing would or I would use that to fill properly. That plug by the way is very low on OEM rearends and runs parallel to the bottom of the axles tubes rather than up at the top like this cover does.



    Here is the original 12 bolt in my chevelle. This cover I installed back in the 80's that has a fill plug. As you can see it's towards the bottom and runs parrallel to the very bottom of the axle tubes. When looking at this rear from the side you can see the factory fill plug in the housing and clearly see that it is perfectly in line with the fill plug in the cover so either plug will fill the rear to the proper level.

    Last edited by Firebirdjones; 09-09-2013 at 04:17 PM.

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    I have the chrome cover that came with my Moser, but ditched that in favor of the aluminum one with bearing supports. They also managed to position the plug perfectly behind the panhard bar for use on our cars. Go figure.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by pajeff02 View Post
    I have the chrome cover that came with my Moser, but ditched that in favor of the aluminum one with bearing supports. They also managed to position the plug perfectly behind the panhard bar for use on our cars. Go figure.
    Yeah, there is no reason why that plug couldn't be in the bottom section just above the drain plug. I really didn't want this cover but they were out of the stocker, so they sold me this one at cost.

    I have since bought a stock painted cover that I will add my own fill plug to, I just haven't had the time to get around to changing it.

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