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Servicing Rear Axle Bearings CJ2A

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Oldpappy View Drop Down
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    Posted: 30 Sep. 2020 at 10:01am
The Dana 41 and 44 axles with tapered shafts are designed so that the axle bearings can be serviced (greased) in place, but it is obvious some people do not know the proper procedure for doing this.

I am in the middle of replacing the bearings and seals in one of my Jeeps and when I pulled the axles I found both tubes nearly full of grease.

There are zerk fittings on top of the bearing flange. There is also a drain plug below this. The intent of the design is as new grease is pumped into the bearing the old grease is pushed out of that drain hole. 

What can go wrong?

 1) If you don't remove that plug before you start pumping grease into the fitting even with good seals the grease will either be pushed past the inner or outer seals and into the axle tube, or out through the front seal. If out the front seal it should drain out through the rear of the backing plate, but only if that drain hole is not clogged with dirt. If clogged it will push past the hub and get into the brake drum.

2) If you do remove the plug, and go too fast, pump too hard the grease will be pushed past one or the other seal rather than into the bearing. Slow gentle pressure is needed to allow the new grease to go into the bearing and push the old grease out through the drain hole.

3) If the seals are bad, and they very often are, the grease will push past the seals as described above into either the axle tube or out through the front.

Here are the steps I use.

A) First remove the drain plug in the axle tube and clean the dirt off the zerk fitting.
B) Make sure the drain hole in the bottom of the hub flange is cleared of dirt and open into the tin cup behind the hub.
C) Attach the grease gun and slowly apply pressure to the pump. 
D) After a couple of slow strokes on the pump the old dirty grease should start coming out of the drain hole.
F) Continue pumping grease slowly until you see clean grease coming out of the drain. This means the bearing has been repacked with new grease.

If you don't see the old grease coming out of the drain hole, there are only two other places for it to go, and it is probably time to replace the seals. 

Replacing the seals requires pulling the hubs and axles, and these have to be put back together correctly.

Axle end play has to be properly set or the bearings will suffer. The hubs must be installed correctly or they will split. If you don't know how to do either of these steps learn how before making the attempt, or get someone who does know how to walk you through it or do it for you. 
 
If you can't get there in a Jeep you don't need to be there
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Bruce W View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 30 Sep. 2020 at 10:37am
Pappy, are you by chance working with an M38 or M38A1 rear axle? I can see where they could have the axle bearing zerk on top and a drain near the bottom, but all of my CJ’s have a zerk Low on the rear side and a tiny vent hole with no plug near the top. I grease them slowly, as you said, until grease starts to come out of the vent hole. 
BW 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 30 Sep. 2020 at 11:00am
Bruce,

It is a 44 with the drums outboard of the hubs so not original to this 47 CJ.

I assumed it was probably early CJ5 but it very well could be a M38 series axle. I do have a military surplus M38A1 axle in the garage for my other project and just looked at that one. It too has the zerk on top of the tube bearing flange and a drain plug. 

I know the M38 series of military Jeeps were water proofed, which would not be consistent with an open vent at that location as you describe. 

This axle also has a vent in the differential cover which differs from the capped vents I have seen on CJ axles, this vent was attached to a hose, but that has been cut off so don't know where it would been routed. In the M38 Jeeps I believe all venting was routed to the air filter. I don't have a known CJ2A axle to compare with these two. It has 5.38 gearing but that doesn't mean much for identification purposes.

The brake backing plates on the axle in the Jeep are not the same as those on the known M38A1 axle I have in the garage, they have the four eccentrics instead of two, and are not as deep as the A1.

I don't remember what the brakes were on the M38 I had 30 years ago, so don't know if they differ between M38 and M38A1, but those could have been replaced so not a good clue.

A lot of folks complain about these axles with the tapered shaft and separate hubs, but one thing I see as an advantage over the later Dana 44's is the axle seals can be replaced without removing the carrier. You do need a good three prong hub puller to remove the hubs without damage, and I use a homemade slide hammer to pull the axles. The split hubs can be used to make a flange for such a slide hammer, so if anyone wants one of the bad hubs I pulled I will gladly send them. 

If you can't get there in a Jeep you don't need to be there
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