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The MJ does not have the original axle that it came with. that one is sitting beside the truck on the ground. i don't know what year the axle that is in it now is. Ive recently been doing the brakes on the truck. The axle on the MJ looks identical to the axle on my 1990 XJ, so I ordered rotors for that expecting them to work. the MJ came with rotors, and worked fine so i didn't expect much trouble.

 

 

That is what happened with rotors for a 1990 XJ. The MJ has a disco axle, so this was a logical solution, right? well it isnt. The rotors that came on the MJ are thicker than the ones that autozone gave me for the 1990. I'm also using the same calipers that were on the 1990...so i thought that the calipers would fit just fine.

 

Here are the ones autozone gave me. .25" thick.

 

Here are the ones that came with the truck...see they're thicker. .5" thick.

 

 

 

SOOOO how do i go about getting the new, thicker rotors? i don't know what year to order them for. ive been searching part numbers, and measurements on napa, and autozone...no real luck yet. Do i just ask for the thicker ones?:wave:

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there's a few differences. I'd take the old ones to the parts store. THe biggest difference is in how tall the "top hate" portion of the rotor is, to accomodate the bearing. It really matters what style and how tall the cap on your unit bearig is.

My d30 has 97 bearings and rotors, but 90 knuckles, so it get's 90 calipers and pads. Try explaining that one to a parts store monkey

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You have to be sure you keep the calipers, rotors and hubs all matched to the axle by year. If you change any one of them to a different listing, you have to change all three. The following is from my forthcoming XJ/MJ book. Please note: It is copyrighted and I am NOT granting you permission to reprint or to distribute it. This is just to help you solve your problem.

 

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.

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Happy to help out. The musical parts guys at Jeep really had a lot of fun regarding the hubs, rotors and calipers. Once you start swapping parts, you have to be really careful to maintain consistency within one range of years.

 

As you discovered ...

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