How to Install Jeep TJ Adjustable Control Arms

Confirm the part and repair scope

The TJ uses coil springs front and rear. Each axle is located by upper and lower control arms plus a track bar. Adjustable arms are sold as front lowers, front uppers, rear lowers, rear uppers or complete sets. Before you start, confirm three things. First, check that the arms are listed for your model year and body. The long-wheelbase Unlimited does not necessarily share every arm length with the standard TJ. Second, check that the adjustment range suits your lift height. Third, check how the arms adjust. Some designs can be lengthened while installed, and others require you to disconnect one end each time you change the length.

Make sure new arms will actually fix your problem. Adjustable arms can correct caster, pinion angle and fore-aft axle position after a lift, and they replace cracked or collapsed factory bushings. They will not cure wander or shimmy caused by a worn track bar, loose track bar mounting points, worn ball joints, tie rod ends, a loose steering box or tire imbalance. Check those parts first. With the Jeep on the ground, have a helper rock the steering wheel while you watch each joint for play. If the main complaint is a driveline vibration, adjustable arms help only when the cause is an incorrect driveline angle.

Prepare tools and safe access

You will need the following: • Sockets and wrenches to fit the arm hardware; • A breaker bar and penetrating oil; • A pry bar; • A floor jack; • Jack stands rated for the vehicle; • Wheel chocks; • A tape measure; • An angle finder; • A torque wrench; • The factory service manual or the arm maker's instructions, for every fastener specification; • Any grease or anti-seize the arm maker calls for; Anyone who can't support the vehicle securely, take accurate measurements or torque fasteners correctly should leave this job to a suspension shop. The Jeep will need a professional wheel alignment afterward anyway.

Vehicle support comes first. Park on level, solid ground and chock the wheels that stay down. Raise the vehicle and set jack stands under the frame rails. Then place the floor jack under the axle so you can raise and lower it while you swap arms. Never work under a Jeep held up only by a jack. Before removing anything, record your baseline: • Ride height at each corner, measured from hub center to fender lip; • The center-to-center length of each factory arm; • Pinion and driveshaft angles from the angle finder; Soak the frame-side bolts with penetrating oil several hours before the job.

Remove without avoidable damage

Replace one arm at a time. While one arm is out, the remaining arms and the track bar keep the axle located. If you pull every arm at once, the housing can roll, the pinion loses its orientation and the coil springs can unseat. Use the floor jack under the axle to raise or lower it until the bolt is unloaded. A bolt that binds is still carrying load, so adjust the jack height rather than hammering it out. A hammer can mushroom the threads or damage the bushing sleeve.

Frame-side bolts on older TJs often seize inside the bushing sleeves. If you need heat, keep it away from fuel lines, brake lines, wiring and the fuel tank area near the rear arms. A bolt that snaps or has to be cut out needs a proper bracket repair, not a smaller replacement bolt. Note which direction each bolt head faces and where every washer sits. When the axle drops, don't let it stretch brake hoses or wiring. Once an arm is out, inspect its mounting brackets for cracks, bends and elongated holes. Repair any damage before the new arm goes in.

Install and restore the system

Set each arm's length before you install it. Use the center-to-center measurement of the factory arm as your baseline, unless the arm maker gives a starting length for your lift. Thread the adjuster evenly and stay within the minimum thread engagement shown in the instructions. Orientation matters as well. Install the correct end at the frame, follow any clearance bend the design includes, and point grease fittings where you can reach them later. Snug the bolts enough to remove free play, but do not torque them yet.

Adjustment depends on which arms you replaced. On the front axle, changing the upper arms relative to the lowers rotates the housing. That changes caster and pinion angle together, so the right setting is a balance between driveshaft type and steering feel. Follow the arm maker's guidance on that balance. Lower arm length moves the axle fore and aft. On the rear axle, the uppers mainly set pinion angle and the lowers set wheelbase. Keep the left and right sides matched, then measure from a fixed frame point to the axle on each side to confirm the axle sits square.

Do the final tightening at ride height. Lower the Jeep onto its wheels, roll it back and forth a short distance to settle the suspension, then torque every frame and axle bolt to the value in the service manual or arm instructions. Rubber bushings tightened with the axle hanging stay preloaded at normal ride height. They wear quickly and can alter the ride. Tighten the jam nuts as instructed, because a loose jam nut lets the arm change length and damages the threads. Grease any serviceable joints before driving.

Check the completed work

Measure ride height again and compare it with your baseline. Then check clearance through suspension travel: • Arms against the exhaust, transfer case skid, fuel tank skid and sway bar; • Brake lines and wiring for slack at full droop; • Tires against arms with the steering turned lock to lock; Recheck pinion and driveshaft angles with the angle finder, and correct any arm that moved while you tightened its jam nut.

Book a wheel alignment. Changing the arms alters caster and can affect toe, and the correct TJ settings come from the service manual, not from guesswork. After the alignment, check that the steering wheel sits centered. Then test drive at low speed before driving at highway speed. Listen and feel for: • A pull or wander; • Clunks over bumps or when braking; • Vibration that rises with speed or load; • Shimmy after hitting a bump

Retorque the hardware after the break-in distance the arm maker specifies. After that, inspect jam nuts and joint play at regular intervals, especially after off-road trips. Some symptoms need further diagnosis: • A clunk when accelerating or braking points to a loose bolt or worn joint. • Vibration under load suggests an incorrect pinion angle. • Steering shimmy calls for checking the track bar, steering components and caster. • Uneven tire wear after the alignment means a measurement or setting should be rechecked.