M38A1CDN2 Brake Job and Hub Removal

[Mike Baker]

Two part question:

1) The maintenance manual says I have to remove the hubs to change out my brake shoes and wheel cylinders - is this true?

And if not, question "2" is what the best method of doing this is. My understanding is that it would be best for me to get a universal hub puller like the OTC 7394, along with a couple of extra legs, and pull the hub using all 5 lugs. However, that particular tool (and the extra legs) will cost me close to $300 in Canada. (Although if I had a US address I could get it for about half that, including shipping - despite the fact that our dollar is worth more). None of the local shops seem to have one I can rent, either.

Any guidance on this would be much appreciated.

Mike

[Barry Churcher]

Mike, surely someone around you has one of these pullers they will lend out. What about the mechanic that fixes your car? Partsource also has a tool rental service if there is one near you. You don't need to pull the rear hubs on a CDN3
model.
Barry

[rob love]

You can easily do the brakes without hub removal. But since your jeep likely has not had a full servicing in 25 years, you should pull the rear axles and repack the wheel bearing on each shaft. Also, replace the inner oil seals, and you may as well replace the outer dust seals. Failure of a wheel bearing will mean the axle will come out, shaft, hub, drum, and tire.

I do have a couple of those OTC hub pullers, and if I was home I would loan you one. Unfortunately I am not, and cannot say for certain when I will be. Do not use a puller that hooks around behind the edges of the hub...you will only bend the hub.

One option to removing the hub is to remove the drum and shoes, then undo the line to the wheel cylinder. You can then remove the 5 or 6 bolts that hold the brake backing plate onto the axle. At that point, the axle should be ready to come out...you may have to tap the hub a bit to get it to come out as you have to drag out the bearing race from inside the housing. Once out, the hub can be removed in a full size press. Then the whole works can be reassembled in the normal manner. On assembly, it is vital that you torque the hub nut extremely tight (I think the torque was around the 300 pound range, but check the manuals). Also, note that the axles should have a slight end play (around.004" IIRC). This is adjusted by removing or installing shims between the race and the backing plate.

Sorry to add this extra step to your brake job, but I am pretty sure when you see the condition of the bearings in there, you will be glad you did.

[Mike Baker]

Ha ha - that is what I feared. Well, no one ever told me this hobby would be cheap. Thank's for the info.

Mike

[chris vickery]

Mike, I ended up in this predicament myself.
My CDN3 had a CDN2 rear axle that needed brakes etc. Upon disassembly, I noted that the rear seals were also leaking. Time to do anoverhaul on the entire axle ass'y...
I tried to pull the hubs using the incorrect puller and let me tell you, my hubs ended up mangled. They are rusted right on, the military never used any anti seize.
I ended up recently purchasing the correct CDN3 differential and axle ass'y to make it right. I figured that if I was going to do a whole rebuild I might as well invest in the correct rear end anyways.
BTW, Partsource does not carry a puller anywhere near the size or type that you require. I would follow Robs advice to pull the axles bearing and all and have the hubs pressed off on an industrial shop press.

[Mike Baker]

After reading this morning's posts, I accepted the inevitable and ordered the hub puller and extra legs from Lordco (which thankfully offers a 30% military discount). This way if there is anyone else on the Island that needs it, I'll have it. (There are at least 3 other M38A1's here - one at the 11 Svc Bn museum, one at the AF museum in Comox, and another privately-owned one that is painted blue).

I have been trying to limit the amount of restoration I am doing on the truck right now, since I don't have a garage - just a carport (historically not much need for garages on Vancouver Island, just for shelter from the rain!). Just waiting for the inevitable posting to Ottawa so I can buy a house with a detached garage/shop where I can do a frame-off restoration without also getting a divorce.

Mike

[Bob Carriere]

Hi Mike

Whenever you get tranferred to Ottawa.....give the Hammond Barn guys a call....

Bob C.

[Mike Baker]

It'll likely be a couple of years yet, but I definitely will look you guys up when I get there!

Mike

[rob love]

Take note of the method used in the Canadian manual to repack the rear wheel bearings on a CDN3. It can also be used to repack the bearings on a Cdn2. Basically you put a whole bunch of grease on one side of the rollers, wrap it all in electrical tape, squeeze the tape, and the grease is forced through the bearings.

Note that some older M38s and M38A1s had a grease nipple on the axle housing over the bearing. This was supposed to grease the bearings, but did not do a good job. As well, if the little drain hole on the bottom of the axle housing flange got plugged up with mud (very common) and excess grease got forced into the brake area. There was a mod instruction to remove the nipples, and replace them with pipe plugs. Bearings were supposed to be repacked on the annual inspection. Truth be told, we rarely did them; usually only when a problem developed.

Also, if there is oil leaking into your brake area through the bearings, you have to replace the inner seal more so than the outer seal. The oil should not even be making it to the bearing. This also applies to the CJ7s. I saw guys continually replacing the outer seals only and not even realizing there was an inner seal.

There, I think I have exhausted that subject. I need to get these things into print: I turned 50 this summer so that means the memory will soon be gone.

[rob love]

Originally Posted by chris vickery

I tried to pull the hubs using the incorrect puller and let me tell you, my hubs ended up mangled. They are rusted right on, the military never used any anti seize.

The military was not supposed to use antisieze on these. The DU (lube chart) did not call for it. The only thing you could use in that spot was lead paste as a last resort if the flange was loose on the axle and re-torquing did not help. If the lead paste did not fix it, then both the hub and shaft had to be replaced, as once bolted together, they were theoretically matched for life.

[chris vickery]

Rob, I don't want to hijack Mikes post but since we are on the subject of axles and diffs, here is a question.
You mentioned re-packing bearings on the jeep.
I am using NOS axle bearings on my CDN3. THe race and bearing comes from Timken as a bonded unit, that is they are fixed together. I have read that over time in use the bearing will separate from the race and when you remove the axle, the race is let behind in the tube. This was the case with the old axle I rescued to use on my CDN3.
Anyhow, I will need to press my bearings and lock collars onto the shaft. It seems easiest to either
1) heat the bearing to 500f and retainer and slip it on,
or, failing luck with that,
2) to get it pressed on.
Option one only works with an unlubricated bearing, is it possible to hand pack it from both sides once in place or should I separate the bearing and race ass'y? How did you do in the military?

[rob love]

The heating method is OK if you have acess to an induction heater. I would not recommend the use of torches to do this job as you can overheat the bearings in spots and bugger the temper.

Pressing is fine. The bearings were packed on the axle in the method I described above: glob grease around the axle on the diff side of the bearing, wrap the glob with electric tape so you form a come from the axle to the bearing, and squeeze the tape to force the grease through the bearing. Then slide the tape cone off the axle.

I am still camping in the tent here in Kandahar, so no illustration of this method. Perhaps if someone has the Cdn 3 supplement to the Cdn2 maintenance manual, they can scan and post the photo of what I am talking about.

[chris vickery]

Thanks Rob, got it. I have the sup that illustrates the method.
I was more curious as to the bearing install. Got it too.