Correct rotors for rear D44 disc conversion?

Hi, all. I'm in the middle of a rebuild on my 1970 CJ-5 Renegade and I have a question on the disc brake conversion I'm doing. For context, I replaced the closed-knuckle front with an open-knuckle D30 from a '73, and the rear axle is the stock D44. I'm using calipers from a '71-'78 Chevy 1/2-ton or light-duty 3/4-ton 4x4 with a Dana 44, caliper mounting brackets from a '73-'91 1/2-ton Chevy 4x4, and rotors from a '77-'78 CJ. Or so I thought. I bought all the new parts a while back and I'm just now putting the rear axle back together, but I found that the rotors don't fit over the axle flange.

The rotors I have are NAPA #4885645, but when I look up the rotors on the NAPA site, I come up with #4885667 for a '78 CJ. There are two fitment issues. 1) The inner hole that should fit over the raised portion of the flange is ~ 3.75" while the raised flange area is ~ 4.12". 2) The "stepped" portion of the brake rotor is ~ 6.5" but the overall diameter of the axle flange is ~ 7", so the rotor obviously won't clear. What concerns me is that the NAPA site info on #4885667 shows the center hole diameter as 3.76" also, so that's still too small. Before I chase my tail anymore, I thought I'd see if anyone happens to have a part number for a rotor that will fit the rear D44 axle flange, or even the dimensions of said rotor. Also, I already purchased longer wheel studs for the front, but I'm having trouble locating longer replacement studs for the rear D44. Anyone happen to have a Dorman part number?

Thanks in advance!

 

Good luck finding a stock rotor with the correct offset that does not need machining in one respect or another. If you do find one please post it up here.
The stock '78 rotor requires the axle flange to be machined. I'd suggest you look at Suzuki rotors. Or contact R&P at 503-556-8911. They are having rotors manufactured for their rear disc setup that is a bolt on. They may work with the GM calipers and mounts but not sure. Ask for John, he would know for sure most likely.


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Thanks, Nickmil. I thought I might get lucky with an OEM rotor, but sounds like no. ;-) I'll give R&P a call - sounds like he can point me in the right direction.

 

Anyone have any ideas for the longer wheel studs? I checked with Dorman directly, and they said they don't have a stud longer than OEM.

 

Mopar # J5357196. Converts to Dorman # 610-273.

 

Thanks, mortten! Greatly appreciated!

 

I was thinking about this. On the front the rotors are on the back of the bearing hub. I'd try mounting the stock rotor on the back of the axle flange and see how things line up. Probably need to space the caliper mount some but could be the path of least resistance short if buying a kit.


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You may be on to something there. I'll do some experimenting tomorrow to check out the fitment. I'm also checking with several machine shops in the area about machining the axle flanges. That's probably my fallback position. It'd be nice to just buy OEM Chevy rotors when they wear out. Thanks again, I'll update when I have some info.

 

I machined the back of my hubs on a brake lathe using half of the rotor tool. Worked well for 8 years now.

 

Thanks, mortten. Did you machine down the outer diameter of the hub and the hub face? That's where I'm having my two fitment issues with this rotor. "1) The inner hole that should fit over the raised portion of the flange is ~ 3.75" while the raised flange area is ~ 4.12". 2) The "stepped" portion of the brake rotor is ~ 6.5" but the overall diameter of the axle flange is ~ 7", so the rotor obviously won't clear."

Also, did you have to do anything to adjust the spacing of the axle bearing and retaining ring for the caliper/pads to have full range of movement?

Thanks!

 

On this set up the rotors don't go over the hub. The rotors go on the back of the hub. Take a look at this link:
http://www.oldjeep.com/disc.htm

 

Space the caliper bracket if necessary not the axle/axle bearings. Spline engagement into the side gears will suffer otherwise.


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Nick- The link is referencing the fronts and was talking about a spacer under the race. Now that I'm thinking about I don't think I had to turn the rears. The spacing problem was on the front only. OVO: Bolt the rotor temporally to the BACK of the hub and slide it back on the axle. Then see if it lines up.