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Positioning the Seal AMC/Jeep CJ with the Model 20 Rear Axle


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#1 Kevin's 83-CJ8

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Posted 05 July 2014 - 01:45 PM

I am currently replacing the bearings in my Model 20 rear end. I emailed Mr. Ludel about the order of pieces for putting everything back together. That is how I found out about this forum.

 

I have two questions to clear up. First, how tight do you set the inner seal?

Second, what direction does the outer seal face….is it the flatter side that goes toward the bearings?



#2 Kevin's 83-CJ8

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Posted 10 July 2014 - 02:50 PM

I have been watching this for a few days and see that people are reading it but no one has answered. I want to get after the project tomorrow so I thought I would post these pictures to help make my question clearer. What side of the seal faces the bearing? I am calling the two sides the flared side and the flat side. Well, what do you think?? Help.

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#3 Moses Ludel

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Posted 29 July 2014 - 03:52 AM

Hi, Kevin!  Sorry nobody jumped into this question, your photos and questions did post...I'll answer personally.

 

The inner seal is a light tap/fit with a suitable driver.  Often, you can find a large socket that will work here.  The seal must be driven squarely into the bore.  There should be some resistance, not a lot though or the seal will distort.  If the seal has a coated jacket, you do not need to add sealant at the outer edge of the jacket.  If there is no coating, put a film of Permatex 3D or Super Flex on the outer jacket face before driving the seal into position.  Look in the bore, you should see where the original seal jacket aligned.  You'll drive the new seal into that position in the bore.

 

The outer flange seal has the raised portion of the seal facing outward.  The flat surface faces inward.  In your two detailed photos, the first photo (on the left) is how the flange seal should appear when installed.  The thin lip of the seal is a dust barrier, and the heavier lip is the actual oil seal.

 

In the case of the inner and outer seal, make note of the heavier oil seal lips.  The flare of the seal's lip faces inward in each case.  This is to retain oil.  Imagine placing the seal in "backwards".  The oil would easily press past the seal lip.  With the seal lips facing inward, they contain the oil.

 

An example: On engine seals, where there is pressure in the crankcase, the lip also faces inward.  The pressure within the crankcase makes the seal lip press against the shaft.  Envision placing the seal in backward at the timing cover or crankshaft rear main seal.  The lip would open or spread from internal crankcase pressure, and oil would pour from the seal.

 

So, again, make sure the flared seal lips face inward on both axle seals.  Try to position the inner seal close to where it rode on the axle shaft originally.  If there is a noticeable seal groove on the axle shaft, you may be able to adjust the seal's position slightly to run on a fresh section of the axle shaft's polished surface.

 

Make certain that you pack the axle shaft bearings properly!  If you note the design, the bearing is outboard (outward) of the inner axle shaft seal and inboard (inside) the outer flange seal.  In this space, there is no axle shaft lubricant reaching the bearing.  (The inner seal prevents this from occurring.)  The lifespan of the axle shaft bearing(s) depend upon proper grease packing of each axle shaft bearing.  There is no provision for lubricating these axle shaft bearings other than removing the axle shaft.  IF lubed properly, the bearing and grease will go a long while between services.  If you need tips on bearing packing, please ask...

 

I'll watch for your reply and questions, Kevin.  We'll make sure you get a prompt response!  Thanks for participating at the forums, we look forward to your topics and posts.

 

Moses



#4 Kevin's 83-CJ8

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Posted 31 July 2014 - 12:16 PM

Moses,

 

Thanks for the response. I talked with the auto parts dealer and a mechanic and they both assured me that it goes in with the flat part facing the wheel. So I put them both in backwards. Awesome! We will see how long the repair will last with them in backwards. It all fit real well and has .004 play. The axles were loose enough to rotate by hand, but would not move back & forth. So, it felt good. We will see.

 

I want to replace the gears eventually so I will change the seals at that time. I think my gears are 272’s. The guys with 410’s that I ride with can do so much with no gas pedal at all. I have to get on the clutch and gas like I am in a get away car just to make it up easy climbs. They can idle up them. I really want lower gears but like all things Jeep, it is about money and time.

 

Kevin



#5 Moses Ludel

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Posted 31 July 2014 - 02:14 PM

Hi, Kevin...That's why I offered the information on sealing lip design and how to recognize how any lip seal fits up.  The information is universal and will serve well in your future. 

 

The outer seal with flat plate is outboard/outward of the axle shaft bearing and grease cavity.  If the seal fit within the axle housing bore and the plate is flat and secure, the only risk would be wheel bearing grease weeping out into the brake shoe area.  There is not a great deal of pressure in this location, so that's not a large threat.  As for water forging, there would be protection against water entering the bearing cavity, as the lip is facing toward the water pressure!  You also have the minor sealing effect of the dust seal portion of the seal; that may be enough to contain wheel bearing grease.  Not the best situation, but probably not bleak, either!

 

2.72 gears are very tall.  Sounds like there will be a lower ratio (numerically higher) gear set in your near future.  You hinted about one-piece axle shafts, that would be a welcome upgrade after wrestling with these hubs and tapered axle shafts!  The one-piece flanged axle shafts do work well.  I recommend the one-piece axle shafts for any tire size over 33" diameter.

 

Sorry you got misinformation from the local "professionals"...Looking forward to your posts!

 

Moses



#6 Geerhound

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Posted 15 October 2014 - 07:43 PM

Moses or anyone else that can help......

 

I also replaced my seals and bearings on my AMC 20 and the above info was extremely helpful.  I replaced my 2 piece axle and hubs in the process and now have no end play even with two .003 and two .010 on the left side as the TSM states.  I thought the new bearings may not be seated all the way so I pulled everything apart and reverified they were seated properly with my shop press.

 

The bearing cup on the left side seems to be sticking out enough to bind(causing no end play) when the outer axle shaft seal is tightened....hence the reason I thought the bearings weren't seated all the way.  The cup does seat flush when the axle is removed so I know nothing on the axle housing is preventing it from seating.

I also tried tapping on the axles with a soft blow hammer to ensure they were seated all the way but this still didn't allow the bearing cup to seat flush with axel housing.

 

Do I just need to keep adding more shims or what else could it be?

Any help would be appreciated.

 

Andy


08' KTM EXCR 530 running...

82' CJ rebuilding.....

86/88 CR 500 rebuilding....

93' CBR F2 running...


#7 Moses Ludel

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Posted 15 October 2014 - 08:19 PM

Hi, Andy...I know this can be frustrating, however, bearings are such a close match in tolerance between new and slightly worn old cups and cones that you should have clearance very close to the original shim package.

 

Do I understand that you installed one-piece aftermarket replacement axle shafts?  Did you order (or receive) the correct axle shafts for your year and axle type CJ?  There were regular and "wide track" versions of the Model 20 axle.  If you install wide track axle shafts in a narrower track axle, you'd have shaft bearings riding too far out in the housing. 

 

There is a spacer block in the differential that separates the axle shafts.  Assuming nothing is new in the differential, the axle shafts should line up correctly.  I would closely compare the length of your OEM axle shafts and the new axle shafts.  Measure between the inner ends of the axle shafts and the seats of the axle bearings.  These measurements must be the same or very close.  If the new axle shafts are too long between the inner end of the axle shaft and the bearing shoulder, the shafts are too long. 

 

Here is a parts PDF to help illustrate the relationship of these parts, including the axle shafts with both conventional and factory limited slip differentials.  See if this helps clarify:

 

Attached File  Later CJ AMC 20 Axle Shafts.pdf   104.12KB   5 downloads

 

I used 1985 as the model year, though much of this information covers other years of the AMC Model 20.  I can narrow down if you share your model year and just the first part of your VIN with letters, not the actual serial numbers.

 

Moses



#8 Geerhound

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Posted 15 October 2014 - 09:31 PM

Moses,

I appreciate the fast response and compare the axle length and get back to you.  I had a new 2 piece axle set on the shelf and figured since I was replacing the bearings and seals I might as well replace the axles and hubs. 

 

I started this project 17 years ago (the Navy got in the way..hah) and now I am putting this 82' CJ back together.

- sand blasted frame and POR 15 everything (17 years ago)

- bought new skyjacker suspension/shocks and erathane everthing (17 years ago)

- bought new axles,seals,bearings ( 17years ago)

- still need seats, tires, and new carb (good thing I didnt order these 17 years ago..would be bad/dry rotted by now..hah!)

 

Thanks again.

Andy

 

08' KTM EXCR 530

82' CJ

86/88 CR 500

93' CBR F2


08' KTM EXCR 530 running...

82' CJ rebuilding.....

86/88 CR 500 rebuilding....

93' CBR F2 running...


#9 Moses Ludel

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Posted 16 October 2014 - 06:48 AM

Andy...Sounds like catch-up time on the CJ!  Let us know how the axle shafts turn out.  According to references, there's a dramatic width difference between the narrow and wide track housings, the transition is around '81, though Jeep was famous for using up parts in carryover models.  Note that the right and left side axle shafts are not interchangeable and have different lengths.  I'm adding the axle housing and related parts schematics and listings for 1981-86, including AMC Model 20 and the 1986 Dana 44:

 

Attached File  1981-86 Jeep CJ AMC Model 20 and Dana 44 Rear Axle Housings.pdf   85.89KB   2 downloads

 

You may have this down already, but the assembly relationship of the parts is also crucial.  This parts schematic doesn't show the placement of the brake backing plate, which must be in correct order.  With the axle shaft inner seal, axle shaft/bearing and bearing cup installed properly in the axle housing, the assembly sequence is: 

 

1) Shims go directly against the axle housing flange with a light coating of either a thin silicone paste or a sealant like Gasgacinch (as a motorcycle guy, you know what this is!) between the shims and against the backing plate for a moisture barrier.

 

2) Install the brake backing plate next.

 

3)  The flanged seal is outboard of the brake backing plate, the flanged seal's raised portion facing outward as in the parts illustrations.

 

4) The dust shield fits outboard of the flanged plate seal. 

 

Note:  If shims are on the wrong side of the backing plate, the play will be incorrect.  Looking at the axle shaft parts illustrations on Page 102-103 (see my first PDF upload), the backing plate goes between #5 and #6 in the parts illustration.  What Mopar calls a "SPACER" (#5) is actually the stack of individual replacement shims noted as 0.003" thickness apiece...If the axle shafts are swapped left to right, there's also a problem, so measure the lengths closely for each side.  Correct the axle shaft placements if they were swapped.

 

For Jeep CJ owners interested in working on their vehicle, I cover this axle shaft installation in illustrated detail within my Jeep CJ Rebuilder's Manual: 1972-86 edition, available from Bentley Publishers and a number of aftermarket sources, including our good friends and sponsors at Advance Adapters!  The book is comprehensive and earned a Mopar Performance official part number.

 

Enjoyed the glimpse of your KTM EXCR.  The Honda CR500 sounds potent, a notch up from my '84 XR500R in need of some restoration.  Gather that you're also a fan of Pro-Link suspension, a major breakthrough.  The CR500 fits nicely alongside the XR600R, the latter a bit bulkier though better on fuel.  The CR is a wicked, on-the-pipe ride!  Like to hear about the CR, too!

 

Moses



#10 Kevin's 83-CJ8

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Posted 16 October 2014 - 09:03 AM

Andy,  just got this feed and want to add my 2 cents. Mine did the same thing at first. It just did not seat all the way in. What I did was took the old seal (and the nuts and bolts) and used it as a press to get the new bearings to seat all the way in place. It kind of pressed everything flush to the axle-housing end. Just put the old seal back on and tighten it back on and it will flush everything up. Then take it off and you are ready for the new parts.

 

I would make real sure the bearings are all the way down into place on the axle first. You know where they have the round edge that fits into the hilt on the axle that is like a stop for the bearings? Make sure that round side is all the way down onto the hilt. This has to be pressed on some how. On one of them I cut a hole in a piece of wood and slid it over the axle, down on the top of the bearings, and then used a hollow piece of exhaust tube and a hammer to tap the bearings all the way down. They have to sit flush onto that hilt.

 

Kevin



#11 Kevin's 83-CJ8

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Posted 16 October 2014 - 09:09 AM

Andy, one more thing I would check. Because the axle is so heavy, I kept resting it on end to work on this or that. It is possible that you got a piece of junk/debris in the grease on the end of the axle and transferred it into the receiving end of the diff. You may have a piece of debris in the hole of one side or the other. I can see all the way into mine with a good flashlight. If you have something in there, you will be able to see it.

 

Kevin



#12 Moses Ludel

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Posted 16 October 2014 - 09:28 AM

Very helpful pointers, Kevin!  Thanks for jumping into the discussion...I'm sure Andy will benefit from your experience...Thanks much for sharing!

 

Moses



#13 Geerhound

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Posted 18 October 2014 - 05:29 PM

Kevin,

I appreciate the pointers....I thought the same thing about the bearings not being seated all the way so I pulled the axles back out and reverified they were bottomed out on the bearing stops.  I also checked for debri inside and went so much as to use a shop vac with a piece of pvc attached to ensure nothing was inside.

Finally as Moses suggested I compared the old axles with the new and found the new left axle measured 1/16+ longer from the inside spline to the bearing stop!!!  I can only assume this was enough to cause it to stick out and bind once everything was bolted up.

 

I reinstalled the old axles with the new bearings and everything flushed up perfectly and I only had to add 2 shims to get the end play specs. 

 

Thanks Moses and Kevin for the help.

 

Moses awesome site...one stop shop for 4x4 and Dual Sport pax.


08' KTM EXCR 530 running...

82' CJ rebuilding.....

86/88 CR 500 rebuilding....

93' CBR F2 running...


#14 Moses Ludel

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Posted 19 October 2014 - 12:44 PM

Pleased that Kevin jumped in, his additional suggestions can help others, that's what a "forum community" is all about, right?  Great that the CJ is on the comeback trail!

 

The magazine and forums have plenty of room for both 4x4s and dirt/dual-sport motorcycles.  Pleased with the direction we're headed.  I tested the Enerpulse Pulstar PlasmaCore spark plug in the Honda XR350R this morning.  Got a good ride and wound up at the BLM watering trough where I filmed the Jeep XJ Cherokee 4x4 with wild horses in March 2013.  (Fall, there are plenty of stud piles in the area!)  Small world, this 4x4 and dual-sport thing!  We recreate and wind up at the same places.  I'll add a short video to the forums from the ride, living proof that a dual-carbureted vintage XR can still get the job done.

 

Moses




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