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unit bearings, brake rotors and knuckels?????

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ok so i am in the process of bulding a 4:10 disco axel for the front of my manche, but i have a few questions... First my disoc 30 is out of a 2.5xj and I also have a complete non disco axel out of a 96 xj.. my plan is to put the one peice shafts from the 96 in to the disco axle and install a spartan locker witch isent the problem, I have ordered 2nd gen unit bearings and slotted and drilled rotors for the 96 axle and I'm going to be installing that on my disconect axel. My question is can i retain the knuckels and brake calipers from the disco axel or do i need to swap the knuckels over from the 96 axel and aquire some new brake calipers? I havent ordered the brake pads yet and i wold live to know if any one has done this before.... Either way I allready have the knuckels and ive allready ordered the unit bearings and rotors but before i go any further i would love to hear some input. I have read some where on naxja that you have to match the rotors to the unit bearings but it wasent realy clear on the calliper issue i am facing. well let me know if you have any answers thanks..... Tim :typing:

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Earlier and later unit bearings have a difference in "thickness", as do the rotors. Any year unit bearing will fit in any year knuckle, but the unit bearings and rotors need to be the same "generation". If not, either the rotor will sit out too far, or it will hit the knuckle.


Calipers do not interchange. New calipers do not fit on old knuckles and old calipers don't fir on new knuckles. The brake pads are also different and not interchangeable between the two types of calipers.


Knuckles are interchangeable between axles.


So the question is, what year is the disconnect axle?


Most likely, to use the correct pads for those rotors, and thus the correct calipers you will need to swap the 96 knuckles onto the disco axle.



On a sidenote, to use the single piece shaft in the disco axle you will need to install an oil seal in the passenger side of the differential. The stock seal for a non disconnect axle will not fit. I can't remember the part number off the top of my head, but it's in the build thread for the "Pig" in my signature. Page 13 I believe.

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Here ya go. Please note this is from a book manuscript I started awhile back. It is copyrighted and in putting it here for you to view I am NOT giving you permission to reproduce or distribute it anywhere else.


Steering knuckles: There are two designs of steering knuckle, and within each design the left and right sides are mirror image and carry different part numbers. The early knuckles were used from 1984 through 1989. The late knuckles were used from 1990 through 2001.


Hub/Bearing: Three different hub/bearing assemblies were used. The hub/bearing assembly is the same for both sides of the vehicle. The first type was used from 1984 through 1989, and must be mated to the early steering knuckle from the same range of years. The early hub/rotors used tapered roller bearings, which are available as individual replacement parts, and in theory can be rebuilt. In practice, removing the old bearings and installing new ones requires a large arbor press and bearing splitter, equipment not available to the average owner. In practice, even dealerships simply replace the entire assembly, because the labor cost to rebuild would exceed the cost of a replacement assembly.


The second type of hub/bearing assembly was used from 1990 through mid-1999. This hub/bearing assembly mates up with the newer style steering knuckle and is used with composite rotors. Certain years of XJ with composite rotors were subject to a safety recall if they were located in northern “rust belt” states, because of problems with the rotors (see below). When replacing hub/bearings in vehicles within this range of years, unless the vehicle recall history is known it is wise to call a dealer or DaimlerChrysler customer service to determine whether or not the vehicle has undergone the brake rotor recall. If so, confirm which hub/bearing assemblies should be used as service replacements..


The third type of hub/bearing assembly was used from mid-1999 through 2001. This hub/bearing is also used with the new style steering knuckles, and is mated with the newer style cast rotors.


Rotors: Three types of rotors were used. Rotors are the same for left and right sides. The first style of rotor was used from 1984 through 1989. The second style of rotor was used from 1990 through mid-1999. This second style rotor was a “composite” design—the braking surface disc was separate from the center “hat” section, which was stamped from comparatively thin sheet steel. After several years of service, it was found that in states and localities where salt is used on the roads in winter, corrosion of the “hat” section could result in the disc portion separating from the assembly, causing a loss of brakes. A factory recall was issued to correct this problem. The recall affects only vehicles within a range of years, and only in certain states. Anyone owning a Cherokee or Comanche in the range from 1990 through 1999 is advised to call a dealer or DaimlerChrysler customer service with the VIN number to determine if the vehicle is subject to this recall.


Mid-year in the 1999 model year the front brakes were changed to an all cast rotor design. Although the original, early style rotors were also all cast, the new rotors are different from the early ones and carry a different part number. The new cast rotors were used from mid-1999 through 2001. Because 1999 was a transition year, owners of 1999 Cherokees will need the VIN number to determine the correct parts to order when servicing the front brakes or hub/bearing assemblies.


Calipers: Two styles of caliper were used. The calipers are mirror image for the left and right sides and carry different part numbers within each group of years. The early style caliper was used from 1984 through 1989. The later style caliper was used from 1990 through 2001 and is used with both the composite rotors and the newer cast rotors.

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Eagle that antidisestablishmentarianism a realy helpful post.... I guess i will be off to the parts store tomorow to pick up some new ball joints so that i can transfer the corect nuckels over to the axel that I'm bulding..... and as far as the inner axel seals I do know that they need to be changed, (napa pn 11899 for the drivers side and PN 11800 for the passanger side

) I just got done installing the seals today and a spartan locker, but thanks for the heads up. Napa was closed the past two days because of the weather so I ended up using oriley PN 710068 and the passanger side i has to go to our local bearing and seal and the part number from them is SKF 11545 so i think ill be good. thanks guys for the instie...

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not sure it's worth adding to your manuscript,

but AMC Eagle Rotors are also the same as 84-89 XJ/YJ/MJ's.


The Eagle unitbearings are almost the same too, but the inner casting is different/slimmer.



I would buy up factory AMC Eagle rotors when I could find them (cheap) at AMC shows.


Factory rotors were beefy, and high quality, compared to the aftermarket stuff.

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