This procedure covers the removal and replacement of the lateral arm (upper control arm) on the rear suspension of a 2021-2024 Ford F-150 with 3.5L EcoBoost engine.

Warnings

Tools required

Parts

• Lateral arm (upper control arm) × 1 — Use OEM specification
• Cotter pin × 1 — As required for ball joint

Preparation

1. Park vehicle on level ground and engage parking brake
2. Loosen wheel lug nuts while vehicle is on the ground
3. Raise rear of vehicle and support securely on jack stands at frame contact points
4. Remove rear wheel on the side being serviced
5. Spray penetrating oil on ball joint nut and control arm mounting bolts, allow to soak

Procedure

1. 1

   Support the rear knuckle assembly
   Position a floor jack under the rear knuckle or lower control arm to support the suspension assembly. Raise jack just enough to slightly compress the suspension and take load off the lateral arm. This prevents the suspension from dropping when the lateral arm is disconnected.
2. 2

   Remove ball joint cotter pin
   Locate the lateral arm ball joint at the top of the rear knuckle. Straighten and remove the cotter pin from the ball joint castle nut. Discard the old cotter pin as a new one will be installed.
3. 3

   Remove ball joint nut
   Using a socket and breaker bar, remove the ball joint castle nut from the top of the knuckle. Keep the nut for reference to ensure the replacement arm uses the same nut type.
4. 4

   Separate ball joint from knuckle
   Using a ball joint separator or pickle fork, separate the lateral arm ball joint from the knuckle. Insert the tool between the knuckle and control arm, then strike with a hammer or use the threaded separator to apply pressure. The ball joint should pop free. Avoid damaging the ball joint boot if reusing the arm.
   ⚠The suspension may shift when the ball joint separates. Ensure the floor jack is properly supporting the knuckle assembly.
5. 5

   Remove frame-side mounting bolts
   Locate the two mounting bolts securing the lateral arm to the frame rail. These are typically located at the forward and rearward ends of the lateral arm. Remove both bolts completely using a socket and ratchet or breaker bar. Support the arm as you remove the second bolt.
6. 6

   Remove lateral arm
   Once both frame bolts are removed and the ball joint is separated, remove the lateral arm from the vehicle. Inspect the mounting points on the frame and knuckle for damage, excessive rust, or worn bushings.
7. 7

   Prepare new lateral arm
   Compare the new lateral arm to the old unit to confirm correct part. Check that ball joint boots are intact and bushings are properly seated. Clean the ball joint stud and threads with a wire brush. Apply a light coat of anti-seize to the ball joint threads.
8. 8

   Install lateral arm to frame
   Position the new lateral arm to the frame mounting points. Insert both mounting bolts and thread them by hand. Do NOT torque these bolts yet - they must be torqued with vehicle weight on the wheels. Tighten the bolts just enough to hold the arm in position.
9. 9

   Connect ball joint to knuckle
   Align the ball joint stud with the hole in the top of the knuckle. You may need to adjust the floor jack height to align the components. Insert the ball joint stud through the knuckle and thread on the castle nut. Tighten the nut to specification.
   Torque spec

   Ball Joint Nut101 Nm (75 lb-ft)
10. 10

    Install new cotter pin
    Align the castle nut slots with the hole in the ball joint stud. If slots do not align, tighten the nut slightly (never loosen) until alignment is achieved. Insert a new cotter pin and bend the ends to secure.
11. 11

    Reinstall wheel and lower vehicle
    Reinstall the rear wheel and hand-tighten the lug nuts in a star pattern. Lower the vehicle until the wheels just contact the ground but the suspension is not fully loaded. Remove the floor jack from under the knuckle.
12. 12

    Torque control arm bolts with vehicle weight on suspension
    With the vehicle lowered and weight on the wheels (but still supported by jack stands under the frame), torque the lateral arm frame mounting bolts to specification. This ensures the bushings are in their neutral position and prevents binding.
    Torque spec

    Control Arm Bolts165 Nm (122 lb-ft)
13. 13

    Final torque wheel lug nuts
    Fully lower the vehicle to the ground and remove jack stands. Using a torque wrench, torque the wheel lug nuts to specification in a star pattern.
    Torque spec

    Wheel Lug Nuts156 Nm (115 lb-ft)

Reassembly

1. Ensure all fasteners are torqued to specification
2. Verify cotter pin is properly installed and secured
3. Confirm no tools or parts are left in the work area

Verification

• Test drive the vehicle at low speed and verify no unusual noises from the rear suspension
• Check for proper rear wheel alignment - a professional alignment is recommended after suspension work
• Verify the lateral arm ball joint has no play or looseness
• Re-torque wheel lug nuts after 50-100 miles of driving

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