Tighten a worn XJ steering box at the sector lash screw to kill on-center play for free, and know when the box is past adjustment and needs replacing.
The XJ runs a Saginaw recirculating-ball box, and after 100k-plus miles the sector-to-ball-nut mesh wears in the dead-center position where the Jeep spends most of its life. The symptom is a vague, wandering on-center feel and a half-inch or more of free play at the wheel before the tires react. A lash adjustment takes that slop out in minutes. But if the box leaks at the sector shaft seal, has play that returns within weeks of adjusting, or binds at center while still feeling loose off-center, the gear is worn through and adjustment only masks it — that box gets replaced. Tightening the lash is also one of the standard checks when chasing death wobble, alongside the track bar and tie rod.
Steps
Adjustment (no parts, ~30 minutes)
Park on level ground, engine off, wheels pointed dead straight. The adjustment is set on-center, so the wheels must be centered.
Find the lash adjuster on top of the box: a slotted or hex screw poking up through the aluminum cap with a 5/8" lock nut around it. On most XJs you'll need to pull the electric cooling fan (and optionally the air box) for clear access to it.
Hold the adjuster screw still with a 3/16" hex key and break the 5/8" lock nut loose with a wrench. Back the nut off about one turn — keep the hex key seated so the screw doesn't move.
Turn the adjuster screw clockwise in 1/4-turn increments. After each increment, rock the steering wheel by hand and feel the on-center free play shrink.
Stop the moment center play is gone. Going past that point loads the mesh too hard — the box will bind at center and the wheel won't self-center after a turn. If you overshoot, back off until it self-centers freely, then come in slightly.
Hold the adjuster screw with the hex key so it can't rotate, and tighten the 5/8" lock nut against the cap. Recheck feel — locking the nut can nudge the screw.
Test drive. Steering should be tighter on-center and still return to center on its own after a corner. If play comes right back, the gear is worn out — move to replacement.
Replacement (~2-3 hours)
Raise the front, support it on jack stands, and remove the front wheels for room. Place a drain pan under the box.
Disconnect the high-pressure and return lines at the box with a flare-nut wrench. Fluid will drain — let it. Cap or bag the line ends to keep dirt out.
Separate the steering shaft coupler from the box input shaft (one pinch bolt). Mark its clocking first so it goes back the same way.
Remove the pitman shaft nut (1-1/16") and pull the pitman arm with a puller. Do not hammer the shaft — you'll damage the new box. Note the pitman arm's clocking on the splines so the new box indexes the same.
Remove the three frame-side mounting bolts and lift the box out. It's heavy and awkward; brace it as the last bolt comes free.
Mount the new box. Torque the frame bolts to 70 ft-lb.
Reinstall the pitman arm in the same clocking and torque the pitman shaft nut to 185 ft-lb. Replace the lock washer if your box used one.
Reconnect the steering shaft coupler in its marked position and the pressure and return lines. Use a fresh O-ring or sealing washer on the high-pressure fitting if the old one is suspect.
Fill the reservoir with the correct fluid for your year. Bleed: with the front wheels off the ground and engine off, turn the wheel lock to lock several times, topping off, until the level stops dropping. Then start the engine and cycle lock to lock a few more times to purge remaining air.
Inspect for leaks at every fitting, drop the Jeep, and get an alignment check — a new box can change the wheel's centered position.
Why it works
The adjustment costs nothing and removes the single most common source of on-center XJ steering vagueness in under an hour
Tightening the lash is a legitimate diagnostic step — a box that won't hold an adjustment tells you clearly it's time to replace
Replacement restores precise steering and stops a sector-seal leak that otherwise drips onto the frame and crossmember
Trade-offs
Adjustment only redistributes a worn mesh; on a high-mileage box the slop often returns, and that's the signal the gear is done
Over-tightening the lash makes the box bind at center and stops self-centering — a real safety issue if you don't catch it on the test drive
Replacement means cracking the high-pressure line and a full power steering bleed; air left in the system causes whine and foaming
The pitman shaft nut is torqued to 185 ft-lb and the arm needs a puller — this isn't a hand-tool-only job
Tools required
Floor jack and jack stands
3/16" hex (Allen) key for the sector lash screw
5/8" wrench for the adjuster lock nut
Pitman arm puller
Large socket for the pitman shaft nut (1-1/16")
Torque wrench (up to 200 ft-lb)
Metric sockets and wrenches (frame bolts, line fittings)
Flare-nut wrench for the high-pressure line
Drain pan and power steering fluid
Parts
Part
Vendor
Est. price
Reman power steering gear box, 1991-2001 XJ (Saginaw 4-bolt)
RockAuto / NAPA / Cardone
—
Power steering fluid (or ATF+4 per your year's spec)
local
—
Pressure line O-ring / sealing washer (if leaking)
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.