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Disc brake swap

colojeepguy

colojeepguy

Colorado Springs
I have a Dana 30 front axle out of a 73 Commando that I'm rebuilding. Planning to change it from drum to disc brakes.
I have another axle from a late 70's CJ (I think). What all do I need to take from this axle to do the swap? Are the spindles different? Knuckles? How about the stub shafts?
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I would just take it all. I think the disc brake spindle has a larger inner wheel bearing. Or are all D30 spindles the same? Knuckles are the same, if it's the 6 bolt caliper bracket. Buy new rotors and loaded calipers. I think the stub shafts are the same, but if you have both apart, you can confirm that. I ran 30 outers on my front 44 for years, and I bought a complete 30 and just moved all of it over, because D30 knuckles will go on a 44 inner C, same ball joint.
 
I’m doing exactly that to my Dana 30.

What I’ve learned thus far:
The outer axle (outside of the u-joint) has a larger seal surface - and uses a different spindle seal.
The hubs are different / the back side is machined for the rotor.
The spindles are different - the inner wheel bearing is larger.
That makes the wheel bearings different (inner one for sure).
I have two-bolt caliper brackets, so the knuckles are different.

The ring gear in the differential had a 1979 date stamp, so that’s what I use when ordering parts.

Jon B.
 
Jon just realized that he ordered the wrong rotor & pad set!

I selected the six/bolt kit; my brackets are two-bolt. Grrr. They don’t mention the bracket. They have “six bolt knuckle” and “two bolt knuckle “ options. I’m a dope.

How is Rock Auto’s return policy?

Jon B.
 
Disk brake spindles are different than drum. All spindles from d25-d30 will work with the right bearings on any hub…you can mix and match everything with some differences. Forget about swedged hubs. Just throw them out.

I got sick of old junk and bought new disk spindles and disk hubs that are true for the disk surface. I run the same all 4 corners.

There are 2 different rotors. One thick that are early and work with the Gm calipers and then the rest are thin and they work with the jeep later jeep stuff.

Just measure the rotors and use rock auto to replace like with like if you have it complete.
 
timsresort said:
Buy new rotors and loaded calipers
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47v6 said:
I got sick of old junk and bought new disk spindles and disk hubs
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I'm so disillusioned with the quality of new parts (this is a constant problem for me in my line of work) that I plan to re-use as much of the old stuff as possible. I was hoping to use the spindles & bearings off the drum brake axle because they are in very good shape, but it sounds like that's not going to work. We'll see what the disc parts look like when I take it apart.
 
colojeepguy said:
I'm so disillusioned with the quality of new parts (this is a constant problem for me in my line of work) that I plan to re-use as much of the old stuff as possible. I was hoping to use the spindles & bearings off the drum brake axle because they are in very good shape, but it sounds like that's not going to work. We'll see what the disc parts look like when I take it apart.
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The new hubs and spindles are fine, at least the ones I bought. The real problem is that most of the available used hubs are drum and they are not machined true for a disk and if they are might only be 5 hole. I have tried to true them up on my lathe with varying degrees of efficacy with a lot of work. Pressing out the old studs for longer ones sometimes wrecks the hubs (throw out wedged hubs for this reason).

You're going to have to buy new disks and at least remanufactured calipers with new pads anyway. You would use new seals and timken or Koyo bearings, right?

When I have redone my old work, I am appalled by the quality of the garbage I cobbled together to save no money and waste a lot of time. I buy all new and just replace it. If I am concerned about the replacement part quality, which I have no control over, nor do I have control over the available used parts, I just buy new. At least I can send it back and get replacements.

At one time I had 1940's D25 hubs with disk brakes on a D30 axle. I looked at it and just asked, why?
 
The rotors came late yesterday, and are NOT the same as those I removed. The rotors themselves are similar, but are thicker ((Edit)1.125” vs. 0.875”) than the correct ones.

They’re the same as what the Scout Dana 44 has on it; it’s sitting on the shop floor.

I’ve ordered the correct ones and have a return label for these. $30 in extra freight plus a drive to FedEx.

Jon B.
 
Last edited:
77-79? Disks are the 1.125. All after are .875

The 1.125 ones work with GM/gm calipers and the .875 ones are jeep.
 
Basically everything from the knuckle out is different as is the outer axle shaft.
While a drum brake knuckle “can” be used the spindle stud holes must be redrill in the correct clocking, longer studs must be installed, and the knuckle must be ground for caliper clearance.
 
colojeepguy said:
So what exactly do I have here? I want to order brake parts, is this late 70s CJ?
View attachment 103859
View attachment 103860
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That is likely the “six-bolt knuckle” set for a Jeep. The calipers are smaller than what’s on the D44 Scout axle, and look similar to my D30 calipers.

The Jeep hoses that I bought are too short with the lift I have, so I have to add some banjo to AN-3 adapters (short, rigid) to use the AN hoses that were on the drum brakes.

Jon B.
 
I’ll add:

Your rotors are probably 1.125” thick. Mine are 0.875 for the two-bolt caliper bracket.

Jon B.
 
I've said it before, and I'll say it again...the 2 bolt caliper brackets are still a fantastic upgrade over any drum.
I used all '82 front axle components and have a modern vehicle to drive now.
 
I swapped to disc front using 78 parts. A guy was selling everything including the knuckles. I found out the knuckle is different for disc brakes the hard way. I had to "clearance" the drum knuckle to clear the caliper. The spindle bolts are longer on the disc brake set up to make up for the caliper brackets.
 
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