Brake drums

[mrman5917]

I found out from NAPA that my drums (rear at least) are un-turntable. I noticed that most places have different 9" drums for the CJ-3A over the 3B, and at least based on the description it looks like the main difference is how the hub attaches to the drum.

Since the 3B "bolt mounted" drum is cheaper than the original style "stud mounted" style, I'm wondering what the real difference is here. My hubs may be ok (still have to push them off to inspect), but is the only thing I may have to do is replace the hub in order to use the cheaper/newer style drum? Is there any reason I couldn't use the current hub with the new drum if I put the bolt mounting holes in it? Is there another technical reason to not use bolt mounted hubs on an otherwise original brake setup?

[Carls_jeep]

The first thing I will tell you is almost every shop you take the drums to will tell you they can't be turned and they will sell you new drums or rotors. The parts stores are especially bad about doing that.

Next is, find a small shop with a drum/rotor lathe and have him just take a light cut to make them round. A person that knows what they are doing can many times save the drum or rotor. A parts store employee will take more off than is needed if they will do them at all. All that needs to be done is to get them true, not rip metal off.

They will always say the drums are oversize and the rotors are to thin. That is not always the case. I got my own drum/rotor lathe because I knew the drums and rotors were turnable but no one would turn them.

Have a machine shop measure them for you because you can't trust parts houses and a lot of automotive shops. It's a shame but not many are honest out there and that comes from a life long mechanic and machinist. You may need new drums but find out for sure first.

Also, have them check to see if they are egg shaped for that may make them unturnable.

[Gunslinger]

Ditto Carl,
I had all 4 of mine turned at repair shop, you know, the kind of place that fixes cars, not just replaces the broken parts... They are hard to find, and usually have names like "Bob's Repair" or "Walts Garage" , Carl is right, most corporate stores are afraid of the liability of repairing something, the lawyers make them sell new parts so that there is no chance of a legal problem.  I don't think there is any technical reason why you can't turn the drums on your 3A.

[mrman5917]

Thanks for the insight guys, I'm going to take it down to a shop that my father in law told me about when I told him what I was going through. Here's hoping that I can get em turned.

If there is a reason they can't be turned, should I be able to modify my hubs and use a 3B style drum?

[macrisel]

X3 for Carl on finding an actual, real life garage.  Chances are they won't be advertising too much because they won't need to.  These old, heavy drums have quite a bit of material in them compared to newer ones.  They have to be pretty bad to warrant replacement.  I had to replace mine, but they were extremely pitted and looked like they had been sitting in water at some point.  I had ordered an overhaul kit from Kaiser Willys and it came with 2 original style and 2 newer style drums.  A couple phone calls later everything was straightened out and 2 more correct drums were on the way!

[Matto]

Does anybody know the spec for the maximum diameter you can turn these drums to?
Matt

[Matto]

Found a NAPPA parts spec that says the max "discard" size of a 9 inch drum is 9.059. That does not seem like much. Less than 1/16inch in diameter and less than 1/32" distance from shoe to drum.
 I just dropped a pair of drums off to the brake shop today, they said they'd let me know if they were good in a couple days.
 Of course Walcks is have a ten% off Cyber Monday Sale today. �:)
Matt

[Carls_jeep]

The Willys manual says 9.060" is the max diameter. When you machine the drums your supposed to use oversize shoes.

[mrman5917]

I was finally able to get my drums over to a family owned shop that was able to turn them. They look great.

It got me thinking though, about my front drums. The rear drums have the hubs "integrated" on the outside with the studs coming through the back. My front drums, though, don't have that. I noticed in the rebuild thread by Comanche_County that his front hubs were on the outside of the drums. I noticed it on another website that was doing a rebuild also. The only difference I can tell is that they have locking hubs.

So are the hubs supposed to be on the outside, or does that only happen when there are locking hubs involved?

[bretto]

I was finally able to get my drums over to a family owned shop that was able to turn them. They look great.

It got me thinking though, about my front drums. The rear drums have the hubs "integrated" on the outside with the studs coming through the back. My front drums, though, don't have that. I noticed in the rebuild thread by Comanche_County that his front hubs were on the outside of the drums. I noticed it on another website that was doing a rebuild also. The only difference I can tell is that they have locking hubs.

So are the hubs supposed to be on the outside, or does that only happen when there are locking hubs involved?

Sounds like you have a M38 axle or M38 outer axle parts. �Way more user friendly in my opinion.
Look under brakes:
http://www.cj3a.info/cj3a/m38cj3a.html
And you can have locking hubs with that set up.  Here's mine:

[mrman5917]

Interesting. I wonder when that was done.

I haven't started taking apart the knuckles yet, but would M38 parts present any other differences?