Just for clarification, the axle shafts should fit with either style of unit hubs.
IDKN why the ZJ shafts didn't fit, they should.
D30 hubs, rotors, calipers, and axle shafts are interchangeable (1990-2001), and HP vs. LP, and ABS or non ABS. You just need to have the rotor type, match the hub type, cast vs. composite. If the hubs and rotors don't match, the brakes will bind up when you install the tires. The Jeep may not move at all with the brakes binding.
Or, just swap the hubs and rotors as a matched set. The calipers don't matter, cast vs. composite or HP vs. LP.
Three different unit hub/bearing assemblies and disk brake rotor types were used over the years on XJ D30's. The unit hub/bearing are the same part number for both sides of the vehicle. The model years for hub/bearing assemblies were:
1) 1984 through 1989 (early type brake rotors/calipers and roller bearing hubs)
2) 1990 through 1999.5 (composite brake rotors)
3) 1999.5 through 2001 (cast brake rotors).
Two steering knuckle designs were used: 1984 to 1989 and 1990 to 2001. Left and right side knuckles have different part numbers.
Two types of brake caliper designs were used: 1984 to 1989 and 1990 to 2001. Left and right sides are different part numbers.
2000 and 2001 XJ D30 are Low Pinion axles like the Wranglers.
** You need to match the disk brake rotor type and measurements to the unit bearing/hub type and measurements currently on your XJ. Previous owners may have installed different type replacement parts. **
On late 1999 - 2001 unit bearing/hubs the ring around the 36MM shaft retaining nut is almost 3/4 inch tall and the hub has longer lug nut studs than older hubs. This style of hub uses the cast rotor. See the axle shaft picture below.
On early 1990 - 1999 unit bearing/hubs the ring around 36MM shaft retaining nut is about 1/2 inch tall. This style of hub uses the composite rotor. See the axle shaft picture below.
Cast vs. Composite rotors Identification and Measurement -
Lay your old rotor on your bench and measure from the bench to the top of the rotor. Be aware that your rotors may have been replaced before and may have a different physical appearance than described and pictured below.
Composite rotors should have a rounded off corner at the wheel mounting surface and look like two pieces joined together. Composite rotors have a thin sheet metal like appearance at the holes where the lug nut studs come through and measure about 1/8 "(.125) thick in this area. Composite rotors have an overall height of 3 3/16".
Cast rotors have a 90 degree angle edge at the wheel mounting surface and look like they are one solid piece of metal. Cast rotors are thicker at the lug nut stud holes and measure between 1/4" (.250) to 5/16 (.320) in this area. Cast rotors have an overall height of 3 1/16".
*** Parts store replacement rotors may have a different physical appearance, but should have similar measurements to the rotors currently on your D30 front axle. You must measure your current rotors and compare the measurements to the replacement rotors at the parts store before purchasing. ***
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Hub Type Identification -
1999.5 to 2001 unit bearing/hub on the left of the picture uses the cast rotor. 1990 to 1999.5 unit bearing/hub on the right of the picture uses the composite rotor.
Note the difference in the height of the ring around the 36MM axle nut and the different length of the lug nut studs.
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