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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

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




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