[57taskforce]

There’s a few variables that will come into play depending upon which variant of 14 bolt you are converting. If you’ve got a cab and chassis dually like me you’ll note the drum brake backing plate mount flanges are several inches inward of the ends of the spindles because of the narrow wheel mount surface of the cab and chassis. With this axle setup, you don’t HAVE to remove the drum brake flanges if you don’t want to, they will not interfere with disk setup. If you’ve got a single wheel axle, those will very likely have to be removed. It’s worth noting that the axle I’m building is being converted to single wheel in the process of the brake swap. If you’ve got a normal dually axle I’m not exactly sure if you’ll have to remove the flanges or not, I would guess that you would but can’t confirm.

Slip on drums: some ‘90s trucks came with slip on drums that don’t require the removal of the hub to take the drums off. The way I’m going about this swap will not work with those axles because they use a different spindle/hub. However, the swap on one of those axles will likely be easier because I believe you’d be able to use the later model disk brake hubs as well as the brake parts making so all you'd have to do is change to 9/16” studs and then get the disk brake backing plate flanges made and install everything onto the axle. You may also be able to use the 90’s slip on hubs with the slip on rotors from the disk brake axle but they will likely require some machine work to center the rotors onto the hubs. This will make more sense as this progresses and I’ll do my best to highlight what I mean by this as we go.

What I did first was strip both of my axles of their hub and brake parts and compare spindles and hubs between the two as seen below. The disk brake axle has a shorter spindle than the inboard mounted drum brake axle. This forced me to mount the brake rotor behind the ‘89 hub just like the original drum was mounted. If I had tried to make it a slip on rotor setup, because of the longer spindles the the backing plate flange would have to be mounted where the axle tube necks down to the spindle. This will not work. This is where the slip on drum rotors will differ, they have the shorter spindle that the disk brake axles have which I believe would allow you to put it together as a slip on rotor setup.

Here’s a few pictures. First one of the two axles side by side, the disk brake axle is in the rear. Next a picture comparing the spindles of the two. Next is the disks mocked up to the drum brake axle with single wheel hubs.
Last is more mock-up, the backing plate/caliper mount is just resting on the axle tube and the caliper is resting on a Jack stand to get the approximate height and positioning of where the backing plate flanges will be mounted up. At this point I knew the swap would work with the right parts and machine work.