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My CJ8 is pretty much stock and had not been abused. I have replaced the 4.2 with a fuel injected AMC 360. I grin every time I drive it.

The problem with my Jeep's rear-end seems to be axle bearings. They do not seem to make any type of growling noise, but do make a kind of  an occasional thunking sound. When it's rolling at speed it is a thunk-------thunk------thunk. Sometimes it goes away or gets louder when I change direction. I did pump some grease into the zirks on the flange that did seem to help once it made its way around the bearing. Seemed to help for maybe 500 miles or so. I am able to hold the wheel at the 6 and 12 o'clock position and get a little movement. What really seems odd is that I do have a fair amount of run out at the axles.

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Tim D...Do you know what manufacturer built the aftermarket flanged axle shafts and what the intended bearing/shaft end play should be?  I'm unclear of the bearing type, and whether it's a radial roller, caged ball or tapered type roller.  

Let's determine the bearing type and see whether there are specifications on their intended end play.  A place to start...

Moses

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Moses,

Thanks for your response, I hope to pull it apart this next weekend. Still trying to get Taxes done. I had  checked to make sure the wheel was tight. Then pulled the brake drum to open it up. I thought that I would be able to just pull the axle, not realizing that the backing plate would need to come off as well. That is when I discovered the zirk fitting and thought that maybe it had the inter seals. A small amount of gear lube came out when I broke it apart, so still not sure if they had inter seals or not. In any event I will mike it before pulling it completely apart and send you the runout measurement . Frankly I was curious if anyone had ever heard a similar sound, from their CJ's rear. The thunking was strange as it did not sound like it was on every revolution. Maybe 2 to 3 seconds apart, weird in my opinion.

Thank Again, truly enjoy my old jeep.

Tim

 

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Tim D..."Thunking" sounds more like a driveline/U-joint issue or binding.  Do you have a suspension lift with a CV rear driveline?  If a CV joint at the transfer case output end, the standard approach is to roll the rear axle/pinion angle upward to create a 1.5 to 2 degrees U-joint angle with the vehicle at static or curb height (vehicle weight on the wheels/tires).  If you have a stock single-Cardan driveline at the back, the shaft's U-joint angles must cancel each other at static ride/load height.  

Let's discuss the rear driveline arrangement.  Another concern would be the driveshaft's coupler spline engagement, making sure the splines engage properly and the shaft is not bottoming.  Rear driveline slope and U-joint angles are critical.

If lubing the axle shaft outer wheel bearings helps, that's a whole other story...We'll work through it.

Moses

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Moses,

You know that trying to describe a driveline noise is always difficult. I'm running 32X11.5X15 with a 1inch body lift. I will check the u-joints for bind, but it is not that type of sound. Some background on me, I also have a streetrod with a ford 9 inch, so I totally understand what you are saying about driveline angles. My money is still on the outer rear wheel bearings. I will know more when I tear it down. By the way, I had a problem with the 9 inch that drove me crazy for the longest time. In reverse it made the sound of the left side brake shoes making contact with the drum. It would not make the sound in drive. Turns out that bearing race had worn the axle enough to cause just enough movement to change the geometry of its motion in reverse. Now I had never seen a bearing spin the race on the pressed side but that's what it was. A set of $$$$ Moser Axles took care of that problem. I was hopeful that you or one of the members had a similar problem that I am having and would verify it for me.

Tim

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Tim D...32x11.5x15 is a mild tire size approach and should work well for the axle bearing lifespan...Looking forward to your tear down and evidence of a specific problem.  The bearing race(s) could be spinning in your AMC Model 20 axle bores.  Aftermarket parts and a previous installation by someone other than yourself could leave room for speculation.  I'm on board with tearing this down to be sure of the issue.  Remedy any installation issues at the same time.  Verify the lubrication method and seal arrangement.

I'm familiar with Moser Axles for the AMC/Jeep Model 20 axle.  I can think of several possible problems, including a loose or unseated lock ring (press-on type) at the bearing, which would contribute to the excessive end play..  Any of these troubles would require tear down to identify.

If you have time during your work, please furnish photos, we can share comments on your findings!

Moses

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Hello Moses,

After doing the rebuild on my M-20, I managed to spin a hub while driving it around on the street. I never liked 2 piece axles so this was a good reason to go single piece. Based on their reputation, I bought a set of the Moser Engineering axles. Figured it would be a straight forward swap. All I can say is their instructions leave a whole lot to be desired. Looking at their instruction page, #4, this axle bearing stuck out 0.120." Their instruction says to grind the spacer ring to get the desired protrusion. They don't state where to grind to get this correct stick out. The AMC housing I.D. has a series of steps. Perhaps I was over thinking the concept but I decided to try making a taper on the O.D. of the seal end of the spacer ring. That didn't have much effect so I took some off the  seal end. Not much change. Ended up taking it off the bearing end and got the bearing seating @0.08 so it was within spec. Seems like a lame way to do something. Were AMC axle housings made that inaccurately?  

On to the next adventure.. Pressing the bearing on the axle.

Installed the retainer, backing plates, bearing and press ring using a manual 12 T press. Pushed the bearing and ring until I felt a increase in the resistance. Slide the axle into the housing and it is obvious the bearing is not seated as the axle is sitting way too far out of the housing. The SKF 331579B bearing ID is 1.3775, the axle has a stepped bearing surface 1.378 / 1.380. I repressed it until the bearing was obviously stopped. On installing the axle, I discovered that the bearing OD is greater than the backing plate's ID. The bearing has an odd "retention ring" on it that seems to hold the bearing race halves together. Without removing this ring, the backing plate would sit proud of the housing by 0.80." That can't be correct. Without pressing off the bearing, I managed to flex this ring to the point where it broke and the backing plate would now sit flush with the axle housing. This leaves you with very little room to apply the sealer but it can be done. At this point I have to assume the bearing is located correctly on the axle. I believe I am having issues with the axle seating in the locker splines. It feels quite tight and the bearing is still 3/8 - 1/2" away from seating in the housing. I have given the axle some whacks with the dead blow and that seems to have made it tighter in the splines, to the point when I may need a puller to remove it. I wonder if the new locker splines got damaged by the old axle or if it is just a tight fit. Called Moser for direction but they are closed for the weekend.

Seems nothing is ever easy.

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Ok, Beat on the axle with the dead blow a bit more. Got it in to the point where I could fit the 4 retaining bolts. Snugged them up and the axle locks up. Tried whacking it some more and nothing loosened. Backed off the bolt tension and the axle loosened up again. Whacked it some more and re-tightened the bolts. Could tell the bearing was moving. Finally got all the bolts tightened, gave it a few more whacks on the axle and it turns free with no end play. Certainly doesn't seem like the right way to do this.  

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Rinky Dink...The hub loosening issue is not unusual.  AMC recommended installing a new hub each time one was removed from an axle shaft to assure a "fresh" spline cut.  I've marked hubs before removal and had success reinstalling them in the exact same position then setting the shaft nut to the factory specification:  The tension/set for these hubs is not a torque setting (although the start-up setting is 250 ft.lbs. minimum);  the right tension is the stickout length of the axle shaft outer end, measured from the outer edge of the hub.  I have this stickout dimension if anyone needs it, suffice to say I've set these two-piece axle shaft/hubs up by applying the force from my floor jack handle to a 3/4" breaker bar and 6-point socket to achieve the factory stickout length.  My best air impact wrench was totally unable to reach this level of torque.

For those unaware, the OEM hubs on these AMC 20/Jeep CJ axles have no machined splines.  They are cast blank and get their "splines" from the serrated teeth "splines" machined into the factory axle shaft tapers.  This demands scary levels of force to cut these splines and secure the hub properly.  It's very common for installers not to take the torque to this level, and especially with oversized tires, a "spinout" of the axle shaft within the hub is likely.

Let us know how this turns out...If you wind up contacting Moser, I'm curious how they describe the "retention" ring.  Something sounds amiss.  Did you compare axle shaft lengths from the bearing inner side of the axle shafts (where the bearings seat) to the locker spline ends at each side?  The axle shaft lengths are different between OE open and limited slip differentials.  Could that be the issue?  Do you have the OE locker?  Shafts placed correctly right to left?  Is the locker spacer block correct for this application, differential and axle shaft lengths?

Moses

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After re-reading what I wrote, without knowing what I was describing, it sounds a bit like gibberish. A pdf of their instructions.  http://www.moserengineering.com/moser/wp-content/uploads/2010/04/JeepInstructions.pdf

Apparently the second hub also spun. It is so trashed that mu little press wouldn't budge the hub. I had to torch the axle to retrieve the brake backing plate. 

I believe the new axle install problem is tight splines. The only locker Moser warns of is the factory locker as it uses a different carrier. I have a Spartan which fit in the standard carrier. I would assume that it should not be a problem. I test fit the second axle and it too is tight in the locker spline engagement. The axle splines are not tapered so again assume just snug. I'll be carefully checking the bearing, housing and backing plate interface. I really suspect that the ring on the bearing is meant to be removed, even though their instructions don't say to do so. This time i'll silicon the seal end plate and lightly bolt it to the backing plate before pressing the bearing on the axle. 

Went and did some measuring. OD of the axle bearing is 2.535, ID of that odd ring on the bearing is 2.25. ID of the brake backing plate is 2.255, so there you go. I would assume the ring should be removed before pressing. Removing it will leave a step in the bearing to act as a retaining feature.

Edited by Rinky Dink
Additional remarks

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After pondering the situation I came to the conclusion that the instructions left out the need to use OE shims between the axle housing and the backing plate, to take up the spec'ed .02 - .08 bearing stick out. Removing the odd ring from the bearing will result in the bearing cage getting hung up on the backing plate. Couldn't see that last night. I need to stop going this stuff in the dark.
Quite obviously whoever wrote the instructions didn't know that OE setup does not use shims on the right side of the axle. Looks like I need to redo the right side and replace that bearing..

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Can you photograph and post a picture of the "ring"?  I'd like to see it and make an educated guess about its purpose and/or "safety" need.  This is not the bearing retaining lock ring, right?

Moses

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In speaking with Moser, per their instruction, the 0.020 - 0.080" stickout and the resulting preload imparted by the brake backing plate is intentional. I have plenty of experience with tapered bearings and I know how preload is supposed to work. This ring  preloads the roller cage and the outer race. As I read their install sheet the thicker side of the inner race (roller taper) should be pointing toward the center of the axle. This seems counter intuitive to preloading the bearing. It should have opposing force directed through both races. The roller cage should never have any loading. Guess I'll just do what they tell me. I'll need to find a replacement SKF BR9 as I broke the first one.59c064d1c96c3_IMG_20170918_1637131011.thumb.jpg.c74ef06348b28c4404a77cd460b10fa3.jpg

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Sounds like we're old hands at tapered roller bearings, I've been working with them "professionally" for 50 years now...

Your photos are helpful.  Regardless of the engineering soundness, the objective with the supplied ring is clear:  Moser is setting either a specific float range (end play) or roller preload.  The ring is even with the bearing cage and acts as a stop for the movement of the roller bearings outward.  With the cup/outer race open in this direction, there would be no other means for keeping the axle shaft from sailing outward or at least to the backing plate.  The stickout from the housing flange assures that the brake backing plate will act as a fixed stop for the ring and bearing cage.    

When the assembly is fully in place with the backing plate secured, what is the measurable end play of the axle shaft and bearing?  If you use a dial indicator at the end of the axle shaft to check end play, push in fully and pull out fully.  There should be measurable movement.  If not, the bearing rollers are wedged between the inner and outer bearing races and "preloaded".  I'm guessing that's not the case and that the rollers get relieved by the position of the bearing cup?

On that note, does this setup leave the original bearing cup in place?  Is that used as a spacer or stop for Moser's outer bearing cup/race?  Does the spacing control the depth of the Moser bearing cup in the axle housing?  

This is definitely different...Must be a motive here.

Moses

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My major issue with this setup prescribed by Moser is there is nothing to keep the axle from just sliding out of the housing. The outer race, being held by the backing plate, has it's taper pointing outward.  In this position, nothing but the seal is holding the axle in place. For this to work as it should, the bearing needs to be turned 180. I had read all of the AMC / Moser forums and found nothing that actually discussed my concern. Last night I found a Moser axle thread on a Jeep forum. It described a series of immediate bearing failures that was resolved by having a mechanic friend  assist on the 3rd try. I have to assume the mechanic did the install his way. Reading this convinced me I was correct. I stopped by my SKF dealer this morning and asked his opinion. He said that the way it is shown in their assembly diagram is wrong, or at least the bearing wouldn't perform correctly. He also agreed the 0.080" preload was grossly excessive.  (Bending of the backing plate was also in one of the forum threads)

So, I'm going to do it the way I think it should be done. Flip the bearing and use the factory shims to give it 0.015" preload. Put a few miles on it and recheck. 

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Rinky Dink...I, too, was surprised that the backing plate would be a preload determinant.  A backing plate is stamped steel and flexes.  Where's the "preload" specification for that kind of approach?

Has anyone else reversed the bearing direction?  Agreed that the current direction seems to prevent the axle shaft from moving inward.  Outward resistance is strictly the backing plate pressure against the bearing cups.

Let us know what you wind up doing.  As an important point to consider, the factory OE axle shaft bearings are not preloaded.  They call for a 0.004"-0.008" (0.006" preferred) end play adjustment.  Shims are installed only at the left side of the axle to achieve this end play.  

If you set a 0.015" preload on the bearings, which would be zero end play then removing 0.015" shim material to preload the bearings, you will toast the bearings.  I've attached a PDF of the factory axle shaft bearing end play adjustment.  End play adjustment at the left side assumes that you have the OEM slotted spacer block at the center of the differential (which allows the axle shafts to even up).  You are actually adjusting both axle shaft bearings from the left side:

1981-86 Jeep CJ Axle Shaft Bearing End Play Adjustment.pdf

Moses

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