This procedure covers the removal and replacement of the rear lateral arm (also called the upper control arm) on the 2015-2020 Ford F-150 RWD with the 3.5L EcoBoost engine.

Warnings

Tools required

Parts

• Rear upper control arm (lateral arm) × 1 — Use OEM specification
• Ball joint castle nut (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Loosen rear wheel lug nuts while vehicle is on the ground
3. Raise rear of vehicle with floor jack at the rear differential
4. Support vehicle with jack stands under the frame rails
5. Remove rear wheel completely
6. Spray all fasteners with penetrating oil and allow to soak for 10-15 minutes

Procedure

1. 1

   Support the rear axle
   Position a floor jack under the rear axle near the side being serviced. Raise the jack just enough to make contact and support the axle assembly. This prevents the axle from dropping when the lateral arm is disconnected and maintains suspension geometry.
2. 2

   Disconnect the ball joint from the knuckle
   Locate the lateral arm ball joint connection at the rear knuckle assembly. Remove the castle nut from the ball joint stud using a 21mm socket. Note the position of any cotter pin and discard it. Install a ball joint separator tool between the knuckle and the lateral arm. Strike the tool firmly or use a pickle fork to separate the ball joint taper from the knuckle. Once separated, remove the separator tool.
   ⚠The ball joint separator may release suddenly. Keep hands clear of pinch points.
3. 3

   Remove the frame-side mounting bolt
   Locate the lateral arm mounting point at the rear frame rail. This is typically the forward mounting point. Using a 19mm socket and ratchet, remove the bolt and flag nut that secure the lateral arm to the frame bracket. Support the arm as you remove the bolt to prevent it from falling.
4. 4

   Remove the axle-side mounting bolt
   Locate the rear mounting point where the lateral arm attaches to the rear axle housing. Using a 19mm socket and ratchet (or breaker bar if seized), remove the bolt securing the lateral arm to the axle bracket. You may need to adjust the floor jack position slightly to align the bolt for removal.
5. 5

   Remove the lateral arm
   With both mounting bolts removed and the ball joint disconnected, carefully remove the lateral arm from the vehicle. Inspect the mounting bushings and ball joint boot on the old arm. Compare the new lateral arm to the old one to confirm correct part before installation.
6. 6

   Clean mounting surfaces
   Use a wire brush to clean the mounting bolt holes in the frame bracket and axle bracket. Remove any rust, corrosion, or debris that could prevent proper seating of the new lateral arm. Inspect the mounting hardware for damage or excessive corrosion and replace if necessary.
7. 7

   Install the new lateral arm
   Position the new lateral arm into place. Insert the ball joint stud into the knuckle first, then align the frame-side and axle-side mounting points. Install both mounting bolts finger-tight but do not torque yet. The control arm bolts must be torqued with vehicle weight on the suspension.
8. 8

   Install the ball joint nut
   Thread the castle nut onto the ball joint stud. Tighten the nut to the specified torque using a 21mm socket and torque wrench. If the nut does not align with the cotter pin hole at the specified torque, tighten further to the next castle alignment - never loosen to align. Install a new cotter pin if equipped.
   Torque spec

   Ball Joint Nut101 Nm (75 lb-ft)
9. 9

   Reinstall the wheel
   Place the wheel back onto the hub and thread all lug nuts by hand. Tighten the lug nuts in a star pattern until snug but do not torque to final specification yet.
10. 10

    Lower vehicle to load suspension
    Carefully remove the jack stands and lower the vehicle until the full weight is resting on the wheels. The suspension must be at normal ride height to properly torque the control arm mounting bolts. Do not fully lower the vehicle to the ground yet - keep it raised just enough to access the mounting bolts.
11. 11

    Torque control arm mounting bolts
    With the vehicle weight on the suspension, torque both lateral arm mounting bolts (frame-side and axle-side) to specification using a 19mm socket and torque wrench. This ensures the rubber bushings are not preloaded in a twisted position.
    Torque spec

    Control Arm Bolts165 Nm (122 lb-ft)
12. 12

    Final wheel installation
    Lower the vehicle completely to the ground. Torque the wheel lug nuts to specification in a star pattern using a torque wrench.
    Torque spec

    Wheel Lug Nuts156 Nm (115 lb-ft)

Reassembly

1. Ensure all fasteners are torqued to specification
2. Verify the ball joint castle nut is properly secured with a cotter pin if equipped
3. Double-check that control arm bolts were torqued with vehicle weight on suspension

Verification

• Test drive the vehicle at low speed and verify no unusual noises from the rear suspension
• Check for proper rear wheel alignment - vehicle should track straight
• Inspect all connections after 50-100 miles of driving to confirm no loosening has occurred
• Schedule a professional four-wheel alignment as suspension geometry has been altered

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