This procedure covers the removal and replacement of the rear trailing arm (lower control arm) on a 2015-2020 Ford F-150 with 5.0L V8, including disconnection of suspension components and proper torque procedures.

Warnings

Tools required

Parts

• Rear trailing arm (lower control arm) × 1 — Use OEM specification or equivalent HD aftermarket
• Control arm mounting bolts and nuts × 2 — Check if included with arm or purchase separately
• Ball joint castle nut × 1 — M18 castle nut
• Cotter pin for ball joint × 1 — 3.2mm diameter

Preparation

1. Park vehicle on level ground and engage parking brake
2. Place wheel chocks in front of front wheels
3. Loosen rear wheel lug nuts 1/4 turn while vehicle is on ground
4. Raise rear of vehicle using floor jack at rear axle or frame lift points
5. Support vehicle on jack stands at manufacturer-specified frame points
6. Remove rear wheel on side being serviced
7. Spray all fasteners to be removed with penetrating oil and allow 15-30 minutes soak time

Procedure

1. 1

   Support the rear axle
   Position a floor jack under the rear axle housing near the trailing arm mount. Raise jack just enough to contact the axle and support its weight without lifting the vehicle. This prevents the axle from dropping when the trailing arm is disconnected and maintains suspension geometry.
2. 2

   Disconnect sway bar link if equipped
   If the trailing arm interferes with sway bar link access, locate the sway bar link lower attachment point at the axle. Hold the link shaft with an Allen key to prevent rotation and remove the lower sway bar link nut using an 18mm socket. Disconnect the link from the axle mount and secure it out of the way with wire or zip tie.
   Torque spec

   Sway Bar Link76 Nm (56 lb-ft)
3. 3

   Remove ball joint castle nut
   Locate the trailing arm ball joint connection at the axle housing. Remove the cotter pin from the castle nut using pliers or side cutters and discard. Using a 21mm socket, remove the ball joint castle nut completely. Do not reuse the cotter pin.
4. 4

   Separate ball joint from axle
   Insert a ball joint separator or pickle fork between the ball joint stud and axle mount. Strike the tool with a hammer to break the taper fit, or use a threaded ball joint separator and tighten until the joint pops free. If the joint is stubborn, tap the axle mount boss with a hammer while applying pressure with the separator. Once free, push the ball joint stud down and out of the axle mount.
   ⚠Do not strike the ball joint stud directly as this can damage the joint. Use a proper separator tool.
5. 5

   Mark control arm orientation
   Before removing the trailing arm, use a paint marker or scribe to mark the orientation of the arm relative to the frame brackets. This will help with alignment during installation and maintain the original suspension geometry.
6. 6

   Remove front control arm bolt
   Locate the front mounting bolt that secures the trailing arm to the forward frame bracket. This is typically a large diameter bolt running horizontally through the arm bushing. Using an 18mm or 21mm socket and wrench (size varies by specific configuration), remove the bolt and nut. You may need to use a breaker bar if the bolt is seized. Support the trailing arm as you remove this bolt.
7. 7

   Remove rear control arm bolt
   Locate the rear mounting bolt at the rear frame bracket. This bolt also passes through the trailing arm bushing horizontally. Remove the bolt and nut using the appropriate socket and wrench. The trailing arm should now be free from the vehicle. Carefully lower and remove the arm, noting the position of any washers or spacers.
8. 8

   Clean mounting points
   Wire brush the ball joint mounting bore on the axle housing to remove any rust or debris. Clean the frame bracket mounting surfaces and bolt holes. Inspect the threads in the ball joint castle nut mounting area and chase with a thread file if necessary. Clean the bolt holes in the frame brackets.
9. 9

   Install new trailing arm to frame
   Position the new trailing arm into the frame brackets, aligning it with the orientation marks made during removal. Insert the front and rear mounting bolts through the frame brackets and arm bushings. Thread the nuts onto the bolts by hand, but DO NOT torque at this time. Ensure any washers or spacers are in their original positions. Leave the bolts snug enough to hold the arm in place but loose enough to allow bushing movement.
10. 10

    Connect ball joint to axle
    Raise or lower the floor jack supporting the axle to align the ball joint stud with the axle mounting hole. Insert the ball joint stud into the axle mount, ensuring it seats fully through the taper. Thread the new castle nut onto the ball joint stud by hand, then tighten using a 21mm socket.
    ℹ️Always use a new castle nut if recommended by manufacturer or if threads are damaged.
    Torque spec

    Ball Joint Nut110 Nm (81 lb-ft)
11. 11

    Install new cotter pin
    Align the castle nut slots with the cotter pin hole in the ball joint stud. If the slots do not align, tighten the nut slightly until the next slot aligns - never loosen to align. Insert a new cotter pin through the hole and bend the ends to secure. Ensure the cotter pin is properly seated and cannot back out.
12. 12

    Reconnect sway bar link if removed
    If the sway bar link was disconnected, reconnect the lower end to the axle mount. Hold the link shaft with an Allen key and torque the nut to specification using an 18mm socket.
    Torque spec

    Sway Bar Link76 Nm (56 lb-ft)
13. 13

    Reinstall wheel
    Install the rear wheel onto the hub, starting all lug nuts by hand. Tighten the lug nuts in a star pattern with a hand wrench but do not torque yet. Remove the jack stands and carefully lower the vehicle until the tire just contacts the ground but the suspension is not fully loaded.
14. 14

    Torque control arm bolts with weight on suspension
    With the vehicle lowered so the suspension is at normal ride height (full vehicle weight on wheels), torque the front and rear trailing arm mounting bolts to specification. This is critical - the bushings must be torqued at ride height to prevent premature wear and binding. Use a torque wrench and appropriate socket on both the bolt head and nut.
    ⚠This is the most critical step. Torquing the control arm bolts with the suspension hanging will cause the bushings to bind and fail prematurely.
    Torque spec

    Control Arm Bolts165 Nm (122 lb-ft)
15. 15

    Final torque wheel lug nuts
    Fully lower the vehicle to the ground and remove the floor jack. Using a torque wrench and 19mm socket, torque all wheel lug nuts to specification in a star pattern. Make two complete passes to ensure even torque distribution.
    Torque spec

    Wheel Lug Nuts169 Nm (125 lb-ft)

Reassembly

1. All reassembly steps are integrated into the main procedure above
2. Verify all fasteners are torqued to specification before driving
3. Double-check that the ball joint cotter pin is properly installed and secured

Verification

• Visually inspect that all bolts are installed and properly torqued
• Confirm the new cotter pin is installed in the ball joint castle nut and properly bent
• Bounce the rear of the vehicle several times to settle the suspension and verify no unusual noises
• Test drive the vehicle at low speed and verify normal handling with no clunks or vibrations
• After 50-100 miles of driving, re-torque the wheel lug nuts to specification
• Have the vehicle alignment checked and adjusted if necessary, as replacing the trailing arm can affect toe and camber settings

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