88 To 90+ Unit Bearings And Brake Rotors

[ComancheKid45]

Theres always room to learn something new. After purchasing a set of Unit bearings for my 88 Comanche I was suprised to find out the brake rotors would not fit over them after installation. I contacted the company and sure enough they said "These will only work on 1990-1992 Comanches". They excepted them as returns if i so wished... Hmmm I had no idea the hubs and brake rotors changed in 1990. So being the curious person I am off to the garage I went this evening. Seeing as I have a 1990 MJ in the garage I pulled the 88 inside and removed a brake rotor from it and side by side compared it with the 1 from the 90. I found a very minimal difference between the 2 and mounted the larger 1 on the 88 for reference and although it showed tighter tolorences, no signs of interfierance were spotted.

 

So anyway I present to your guys a question. Will the installation of the 90+ unit bearings and brake rotors on an 88 Dana 30 cause any issues? It seems as simple as a bolt on swap, considering the brake pads are the same and the rotors are a mearly 4mm difference in diameter, the biggest difference is the diameter of the center sections allowing the 90+ rotors to fit over the larger unit bearings.... Sorry if I rambled on a bit, but i figured if anything it could be an intresting topic for future reference and hopefully someone else could learn this fact just as I did today.

 

Thanks guys!

[Eagle]

From the book manuscript I started several years ago (permission to reproduce is NOT granted):

 

In general, the parts to be concerned with in keeping the front brakes compatible are the steering knuckles, the hub/bearing assemblies, the rotors, and the calipers. (There is a more complete enumeration of the interrelationship of these parts in Chapter 6, Axles.)

• Only two steering knuckle designs were used: 1984 through 1989, and 1990 through 2001. Left and right side knuckles are different part numbers within each group.
  

• Three different hub/bearing units were used. The hub/bearing units are the same for both sides of the vehicle. The different years for hub/bearing assemblies were: 1984 through 1989; 1990 through mid-1999 (composite rotors); and late-1999 through 2001 (cast rotors).
  

• Three rotor types were used: 1984 through 1989; 1990 through mid-1999 (composite); and late-1999 through 2001 (cast).
  

• Only two caliper types were used: 1984 through 1989, and 1990 through 2001. Left and right side calipers are different part numbers within each group.
  

The front hub/bearing units are usually serviced by replacement. The early (1984-1989) hubs use tapered bearings, while the newer hubs use ball bearings. Replacement bearings and oil seals are available for the early, tapered-bearing hubs. However, service requires a heavy-duty shop (arbor) press to remove the old bearings and install the new ones. Unless you have access to a shop press with bearing removal fittings, attempting to rebuild a hub assembly is probably not cost-effective unless you have access to the equipment needed to perform the work yourself.

 

To answer your question, to use the '90 brakes on the '88 axle would also require replacing the calipers and steering knuckles.

[Biotex]

Curious who you purchased them from. Sounds like they have decent customer service at least.