Moses Ludel’s 4WD Mechanix Magazine – Moses Ludel Rebuilds the Jeep XJ Cherokee 8.25″ Chrysler Axle
This installation includes an ARB Air Locker differential and upgrade axle shafts!
Hordes of XJ Cherokee models now ply the rough backcountry—and for good reason! With its 101.4-inch wheelbase, light curb weight, proven Jeep powertrain components and axles that rival the Wrangler models, the XJ Cherokee works well both on-highway and in challenging terrain! Its transfer case tucked neatly into the unitized chassis, the longer wheelbase XJ has more breakover clearance than a Wrangler. The wheelbase provides stable, predictable, all-season highway handling.
The reverse-rotation (high pinion) Dana 30 open-knuckle front axle is common to all XJs. 1984-90 models have a vacuum disconnect front axle system much like the YJ Wrangler. ’91-up versions have one-piece inner axle shafts at each side—similar to a TJ Wrangler’s approach. At the rear, a Dana 35/35C (C-clip or non-C-clip axle shaft types) is popular in many XJ Cherokee applications, especially those with the ABS option. Chrysler’s own 8.25” C-clip axle assembly commonly fits non-ABS XJ Cherokee applications from 1991-up.
Jeep fans familiar with the Spicer/Dana axles and even the AMC Model 20 (CJ and J-truck era) axle find the Chrysler 8.25” axle unique. This is not a new design, however; Chrysler has used the 8.25” and larger versions of this axle type for many years in the Dodge Ram, Dakota pickups and rear drive cars. An 8.25” Chrysler axle buildup covers a range of Jeep and Dodge truck applications!
Some XJ Cherokee builders retrofit the Comanche pickup’s Dana 44 (8.5″ ring gear diameter) or Ford’s 8.8” or 9” assembly in place of the 7.562” Dana 35/35C. In my view, the original Chrysler 8.25” axle may well be worth keeping! Both ARB Air Locker and Superior Axle & Gear offer 8.25” upgrade components that enhance this axle. With 33” diameter tires and a 6-inch long arm suspension package, my ’99 XJ Cherokee has proven its worth as a dual-purpose highway and trail machine. If 33″ tires meet your needs, the 8.25″ Chrysler/Jeep axle is ample. Follow along as I highlight the build-up of an XJ Cherokee 8.25” rear axle!
Step 1: This stone stock 1999 XJ Cherokee was a find in 2005. ’99 means OBD-II diagnostics, the last 4.0L MPI inline six with a distributor ignition and the ’97-up body design. The stock rear axle is an 8.25” Chrysler, which has a larger ring gear and beefier axle tubes than the 7-9/16” Dana 35 and 35C designs.
Step 2: The axle buildup is for 33” diameter tires and serious trail running. An ARB Air Locker provides manual lockup, a feature that I prefer for multi-purpose use. ARB Air Lockers are available for both the Dana 35/35C and 8.25” Chrysler axles found in the XJ Cherokee. Adding 4.10:1 ring-and-pinion gears, a quality overhaul kit and tough 29-spline replacement axle shafts turns this rear end into a Superior Axle & Gear ‘Super 8.25” with ARB Air Locker’ upgrade!
Step 3: ’99 models were well into the post-asbestos brake lining era, but replacement, non-OEM generic brake lining can contain asbestos. At 94,000 miles, this XJ Cherokee could have aftermarket brake lining…I use an AMMCO Brake Washer to safely work with brakes and clutches. Gear lube drains from the differential while the brake drums come off. This brake parts washer captures brake dust in an aqueous cleaning solution that will not harm rubber or sensitive parts.
Step 4: Removing axle shafts on any C-clip axle requires loosening the differential mate shaft. Use caution when loosening the special lock screw that holds the mate shaft in place—do not break this screw! Once the shaft is safely out, you can tap the axle shafts inward and remove the C-clips. The axle shafts should slide out easily at this point.
Step 5: Axle shafts out, the bearing caps can be loosened. Mark the bearing caps for their proper position. Use care, loosen bolts evenly and do not allow the differential and ring gear assembly to fall out of the housing! You may need extra help here. Working alone, I often use tie-down straps to hold the carrier in place when removing the bearing caps.
Step 6: Now you can remove the pinion shaft by first loosening the yoke nut. The yoke/flange should pull free with a simple two-jaw puller. Be careful not to damage the yoke saddles! Once the yoke is free, the pinion shaft is still secured by the press-fit front bearing. Here is a technique I use when the original bearing cone and cup will be replaced:
Step 7: You can drive the bearing cups out—evenly—with a brass punch and hammer. However, this is the Jeep factory recommended method. A special bearing cup driver not only drives straight and true, it spreads the force around the cup edge and quickly loosens or seats a bearing cup. If you do a lot of this work, invest in tools. Once the bearing cups are removed, I wash the cavity out with solvent.
Step 8: Before drilling, make sure you have the air fitting in the right location. ARB recommends drilling the straightest hole possible. When accessible, drill from the top of the housing downward. On the 8.25” axle in an XJ, I find that drilling from the bottom proves practical, keeping the drill motor close to the housing. Using a quality ¼”-NPT tap, you can make the fitting threads nearly vertical. Before drilling, pack rags in the axle housing tubes. After drilling, vacuum all metal debris from the housing, the drilled hole and the newly cut threads. Use the tap carefully; avoid tap seizure or risk of tap breakage!
Step 9: Air fitting threads and the housing cleaned thoroughly, you can now drive the bearing cups into place. Here, I use a factory-recommended driver to install the inner pinion bearing cup. Both ARB and Superior Axle & Gear use genuine Timken bearings to assure quality and proper fit. Oil cups lightly to prevent seizure. Drive the pinion bearing cups straight and true until they seat firmly.
Step 10: New Superior Axle & Gear pinion shaft is at right, new shims in the foreground. The new pinion gear has zero-variance (0.000” depth error). To determine the new shim stack thickness, I begin with the original pinion gear’s “+3” (+0.003”) mark as a guide. To properly position the original gear at the factory took 0.003” less shim stack thickness than a zero variance gear would require. To locate the new “+0” gear at the correct position in this axle housing, I add 0.003” of shim material to the original shim stack height. (This creates a shim stack that is 0.003” thicker than the original factory shim stack.) Place the shim stack between the pinion gear head and the rear bearing.
Step 11: A simple bottle jack press is adequate for installing the new pinion bearing. Shims in place, I use my easily constructed black pipe sleeve tool to press the lightly oiled bearing onto the new pinion shaft. The tool fits neatly inboard of the bearing rollers and cage. It presses only on the inner bearing race/collar. Seat the bearing fully. Install the differential carrier bearings in the same way. Make certain not to press against the steel cages or rollers!
Step 12: Always install a new crush sleeve before placing the front bearing in position. I use this factory tool to squarely install the front pinion bearing onto the pinion shaft. The U-joint yoke, without the pinion seal installed, serves as a fixture for pushing the bearing into place. This tool threads onto the pinion shaft and applies pressure directly to the flange’s nut seat, bringing the new bearing quickly into position. If you do not have access to such a tool, you can hold the yoke securely with a pipe wrench or holding fixture and use an old flange nut to seat the yoke and bearing. Do not attempt to crush the sleeve at this point. Remove the yoke with a two-jaw puller.
Step 13: With the new pinion seal driven squarely into position, I coat the yoke splines and the seat end of the yoke with Super 300 sealant. This is insurance against oil “wicking” out the yoke. I coat the pinion seal lip with grease and install the yoke once more. This time, I apply Loctite 242 to the threads of a new flange nut supplied in the Superior Axle & Gear overhaul kit. Always use a new nut, and tighten the yoke up squarely to protect the seal. This overhaul kit is thorough and of top quality.
Step 14: Here, I very carefully set the pinion bearing preload to specification. The new sleeve requires a minimum of 210 ft-lbs of torque to crush it. Once that torque is reached, set the pinion bearing preload by continuing to tighten the nut—very slowly to avoid over-tightening the bearing preload! It is critically important to just bring the pinion bearing preload up to specification. On this 8.25” axle with new bearings, I strive for 15-30 in-lbs of load/drag, tested over 360-degrees of rotation.
Step 15: Make sure the carrier and ring gear faces are true and clean. Always install new ring gear bolts. The Superior Axle & Gear overhaul kit is complete with bolts. I use red 271 Loctite on these left-hand threads. Tighten bolts in cross, bringing up tension gradually to 70 ft-lbs. Check the final torque a few times, then check once more after parts have settled for a few minutes.
Step 16: The threaded adjusters at each bearing cap have hex-head center openings. Adjusters can be reached by inserting a long ½”-drive extension through the axle tubes with a ratchet or torque wrench attached outboard of the wheel/axle shaft bearing openings. Although there is a special tool for this purpose, I made this one to perform the same role. Securely weld a large nut (sized for the bearing adjuster’s hex opening) to an old ½-inch drive socket. Add some small spot weld stops at the top of the hex flats to prevent the hex tool from passing through the adjuster.
Step 17: Set the adjusters squarely into their saddles, just outboard of oiled, new bearing cups. Using Loctite 242 on clean threads, torque the upper bearing cap bolts to 10 ft-lbs with the lower bolts turned finger tight. Seat carrier bearings by rocking the pinion gear back and forth as you adjust the gear backlash with the special hex tool. Use a long extension, routed through the axle tubes, to turn the hex tool and adjusters. Adjust the ring-and-pinion gear backlash; for now, apply only light carrier bearing preload.
Step 18: Using a dial indicator, check backlash at several points on the ring gear. At the narrowest backlash point, I set the backlash to 0.006”. With a factory recommended backlash variance of up to 0.003” for the 8.25” axle, this means my widest backlash should be no more than 0.009”. (Preferred factory backlash setting is 0.006”-0.008” with 0.005”-0.010” acceptable.) Once the ring gear backlash is within range, cinch the bearing cap bolts in cross and gradual stages to 70 ft-lbs. Rocking the pinion gear to seat the bearings, I carefully torque each adjuster to 75 ft-lbs—without losing the backlash measurement. Check final backlash with the adjusters each secured at 75 ft-lbs. If necessary, re-adjust gear backlash and torque settings.
Step 19: The final test of any ring-and-pinion set up is a tooth contact pattern. I coat the gear teeth with the supplied test paste and use a rag or strap to create resistance at the pinion yoke. Rotate the ring gear steadily in each direction. Here, I hold the twisted strap around the pinion and use a box wrench to rotate the ring gear. Create only enough resistance at the pinion to make a clear tooth impression in the paste. Once a correct pattern has been confirmed, install the adjuster retainer plates to prevent the adjusters from rotating. Use Loctite 242 on bolt threads.
Step 20: Superior Axle & Gear replacement axle shafts are induction hardened with rolled splines. 29-spline (the stock 8.25″ axle count) replacement axle shafts with an ARB Air Locker create a ‘Super 8.25” with ARB’ package. Here, I install the new axle shaft bearings and the seals supplied. With the old seal removed, this factory tool makes quick work of bearing removal. The tool is available through your local Jeep/Mopar parts source or an aftermarket tool supplier like Miller/SPX or OTC. One alternative is a universal slide hammer puller, but wear safety goggles!
Step 21: I use the factory-recommended driver for installing a new axle shaft roller bearing. The letters and numbers on the bearing shell face outward. Oil the bearing lightly and drive it squarely until seated firmly. Install the new seal squarely and carefully. Grease the seal’s lip and install the axle shaft carefully. Avoid damaging the seal lip.
Step 22: Both axle shafts tapped lightly through the side gears, you can install the C-clips then the spacer mate shaft and lock screw. I always use a new lock screw and Loctite 242, setting torque to a minimum of 8 ft-lbs. Here, I check clearance between the axle shaft inner ends and the “mate” spacer shaft. Use the ARB instructions and/or the factory specifications to verify correct shaft end float for your Jeep XJ Cherokee application.
Step 23: Final view shows air tube shaped for a minimum of 5/16” spacing away from moving parts. Handle the tubing carefully. I form it to stay inboard of the axle housing on this particular application. Visualize how the tube will hold up over time. Avoid rough edges or chafing surfaces. Place cover sealant around the housing as shown. Torque stock cover bolts to 30 ft-lbs.
Step 24: This is the assembled view: new Superior Axle & Gear axle shafts, freshly painted brake drums and a fill of genuine Mopar 75W-140 Synthetic Gear Lubricant (P/N 04874469). Add the ARB Air Locker air supply and electrical system, and the axle is ready to go! This XJ Cherokee will receive a 6-inch long arm suspension package and 33″ tires. See the matched 4.10:1 gearing and ARB-equipped front axle ‘how-to’ feature (“Moses Ludel Rebuilds the XJ Cherokee Dana 30 Front Axle”) for further details.