The rear leaf springs hold up the back of the XJ, set ride height, and locate the rear axle — when they sag, crack, or wrap up under load, replacing the pack restores height, ride, and control.
The XJ rides on a leaf-sprung rear axle, and those springs do three jobs at once: carry the load, set how high the back sits, and keep the axle from walking fore and aft. Decades of weight, heat cycling, and rust flatten the arch until the back end squats, the ride goes harsh, and the axle starts to wrap up under throttle. You'll feel it as a saggy stance, bottoming over bumps, or axle wrap that makes the rear hop on acceleration. Swapping the pack — whether back to stock height or up to a lift spring — brings the geometry back and is the foundation of most rear lifts. Do one side at a time so the axle never drops free, and budget extra time for seized fasteners on any Jeep that has seen winters.
Steps
Park on level, hard ground and chock the front wheels. Loosen the rear lug nuts while the tire is still down, then raise the rear of the unibody and set jack stands under the frame rails behind the rear seat area. Leave the axle hanging or support it on a second jack so you control its height.
Soak every fastener now: the four U-bolt nuts, the front spring-eye bolt at the hanger, and the upper and lower shackle bolts. These have sat in road grime for decades — give penetrating oil time to work, ideally an hour or overnight on a rust-belt Jeep. This step saves the job.
Remove the rear wheel and support the axle on a jack so it can't swing down when the spring comes loose. Work one side only — the opposite spring keeps the axle located while you do this side.
Disconnect the rear shock lower mount and the rear sway bar end link on this side to give the axle room to droop and to unload the spring.
Remove the four U-bolt nuts and lift off the lower spring plate (the perch that the U-bolts clamp the axle to the spring with). Plan to replace the U-bolts — they stretch on first torque and reusing them risks a loose perch. Note how the spring centering pin indexes into the axle perch before anything moves.
Lower the axle slightly with the jack to separate it from the spring. The axle now rests on its jack while the spring is free at the center.
Remove the front spring-eye bolt at the forward hanger. This is the most commonly seized fastener on the whole job — work it back and forth with penetrating oil rather than forcing it, and have a breaker bar ready. If the sleeve spins inside the bushing, you may need to cut the bolt with a saw or air tool.
Remove the shackle bolts at the rear and lift the old spring out. Inspect the shackle and both hangers while the spring is out: cracked welds, rotted shackle plates, and rusted-through hanger brackets are common and are the right time to fix or reinforce. A blown shackle bushing on its own is a cheaper fix than a full pack.
Set the new spring in place. Hang the front eye on the forward hanger first and run the bolt in hand-tight so the spring can pivot. If you're installing a greasable bolt, grease it on the way in.
Swing the rear eye into the shackle and install the shackle bolts hand-tight. The holes rarely line up on the first try — pry the spring or nudge the shackle until the bolt drops through. Confirm the shackle hangs at the correct angle; a shackle pulled fully forward or backward means the spring length or lift is wrong for your setup.
Raise the axle back up with the jack until the centering pin on the spring drops into the locating hole in the axle perch. Seat it fully — this pin sets fore-aft axle position, and a missed pin lets the axle shift.
Install the new U-bolts over the axle and through the lower spring plate, then run the nuts up evenly in a crisscross pattern so the plate seats square. Snug them but leave final torque for ride height.
Reconnect the shock and sway bar link on this side. Repeat the entire process on the opposite spring.
Lower the Jeep so the suspension carries its full weight at ride height, then do the final torque on everything. Commonly cited XJ figures: U-bolt nuts to about 52 ft-lb (verify against your bolt size — larger 9/16" U-bolts spec higher), front spring-eye bolt to about 115 ft-lb, and shackle bolts to about 80 ft-lb. These vary by year and by aftermarket kit — confirm against your factory service manual or the spring maker's instructions and follow their spec if it differs.
Torque the rear lug nuts to 95 ft-lb, drop the Jeep fully, and test drive at low speed first. Recheck the U-bolt nuts and shackle bolts after the first 50 to 100 miles — fresh U-bolts settle and the perch can loosen if you skip this.
Why it works
Restores ride height, ride quality, and proper rear axle location in one job
Fixes axle wrap and the harsh, bottoming ride that comes with sagged springs
Doable in a driveway with hand tools, a torque wrench, and patience
The foundation of most rear lifts — new springs are the right place to add height
A chance to inspect and fix hangers, shackles, and bushings while everything is apart
Trade-offs
Seized front spring-eye bolts are the norm on older or rust-belt XJs and can turn an afternoon into a fight, sometimes needing a cut-off tool
Rotted shackle plates or hanger brackets can expand the job into bracket repair or replacement
Reusing old U-bolts risks a loose perch — budget for new ones
Final torque must be done at ride height, and the fasteners need a recheck after the first drive
Tools required
floor jack and jack stands (two jacks help)
metric and SAE sockets
torque wrench
breaker bar
penetrating oil
C-clamp or spring spreader
pry bar
wire brush
thread locker (blue)
Parts
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Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.