Radius Arm

Removal and replacement of the front suspension radius arm (lower control arm) on a 2008 Dodge Viper, including ball joint separation and bushing inspection.

Warnings

Tools required

Parts

• Radius arm (lower control arm) × 1 — Use OEM specification
• Radius arm bushings (if not included with arm) × 2 — Use OEM specification
• Ball joint castle nut × 1 — Use OEM specification
• Cotter pin × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks behind rear wheels
3. Loosen front wheel lug nuts while vehicle is on ground
4. Raise front of vehicle and support securely on jack stands at manufacturer-recommended lift points
5. Remove front wheel on side being serviced
6. Spray all radius arm fasteners with penetrating oil and allow to soak for 10-15 minutes

Procedure

1. 1

   Remove ball joint cotter pin and castle nut
   Locate the ball joint connection where the radius arm attaches to the steering knuckle. Straighten and remove the cotter pin securing the castle nut. Using the correct size socket (verify against manufacturer specification), remove the castle nut from the ball joint stud. Do not discard the castle nut unless replacing; inspect threads for damage.
2. 2

   Separate ball joint from steering knuckle
   Position a ball joint separator tool between the radius arm and steering knuckle at the ball joint taper. Strike the tool firmly to break the taper fit. If using a pickle fork, note that this may damage the ball joint boot. Once taper is broken, the ball joint stud will separate from the knuckle. Support the radius arm to prevent sudden dropping.
   ⚠Ball joint may release suddenly under spring tension. Keep hands clear of pinch points.
3. 3

   Disconnect sway bar end link from radius arm
   Locate the sway bar end link attachment point on the radius arm. Remove the fastener securing the end link to the radius arm. This is typically a single nut on a threaded stud. Use a Torx or hex key to hold the stud from spinning while removing the nut. Disconnect the end link from the radius arm.
4. 4

   Remove rear radius arm pivot bolt
   Locate the rear mounting point where the radius arm pivots on the crossmember. This is a large through-bolt with a bushing. Remove the nut from the rear pivot bolt, then drive or press the bolt out of the bushing assembly. Note the orientation of any washers or spacers for reinstallation.
5. 5

   Remove front radius arm mounting fasteners
   Locate the front mounting point of the radius arm to the crossmember or frame bracket. Remove the 2 bolts securing the front bushing bracket to the chassis. These bolts pass through the bushing housing and into the frame. Use a breaker bar if fasteners are seized.
6. 6

   Remove radius arm from vehicle
   With all fasteners removed and the ball joint separated, lower the radius arm from the vehicle. Maneuver the arm clear of the steering knuckle, sway bar, and any brake line brackets. Inspect the removed arm for damage, bent condition, or torn bushings.
7. 7

   Inspect and replace bushings if necessary
   Inspect both front and rear bushings in the radius arm for cracking, tearing, or separation from the metal sleeve. If bushings are worn, press them out using a hydraulic press and appropriate adapters. Press new bushings into the radius arm housing, ensuring proper alignment and full seating. If installing a new complete radius arm assembly, skip this step.
   ℹ️Bushing replacement requires specialized tools. Consider professional service if press equipment is unavailable.
8. 8

   Install radius arm to front mounting position
   Position the radius arm to the front mounting bracket on the crossmember, aligning the bushing bracket with the bolt holes. Insert the 2 mounting bolts through the bracket and into the frame. Thread bolts by hand to start, but do not fully tighten yet. Suspension fasteners must be torqued at ride height or with suspension loaded.
9. 9

   Install rear radius arm pivot bolt
   Align the rear bushing of the radius arm with the mounting point on the crossmember. Insert the pivot bolt through the bushing and crossmember bracket. Install any washers or spacers in their original orientation. Thread the nut onto the pivot bolt by hand, but do not fully tighten yet.
10. 10

    Connect ball joint to steering knuckle
    Lift the radius arm into position and insert the ball joint stud into the tapered hole in the steering knuckle. Install the castle nut onto the ball joint stud and tighten to draw the taper fully seated. Once seated, tighten the castle nut and align the slots with the cotter pin hole. Install a new cotter pin and bend the ends to secure.
    ⚠Castle nut must be tightened to specification, then advanced to next slot if necessary for cotter pin alignment. Never loosen the nut to align slots.
11. 11

    Reconnect sway bar end link
    Reconnect the sway bar end link to the radius arm mounting point. Install the fastener and tighten while holding the stud from spinning. Ensure the end link is properly seated in the mounting hole.
12. 12

    Torque all radius arm fasteners
    Support the suspension at normal ride height using a floor jack under the radius arm or lower ball joint area. With the suspension loaded to simulate ride height, torque the front mounting bolts, rear pivot bolt nut, and ball joint castle nut to manufacturer specifications. Verify cotter pin is properly installed and bent.
13. 13

    Reinstall wheel and lower vehicle
    Reinstall the front wheel and thread lug nuts by hand. Lower the vehicle until the tire just contacts the ground. Torque the lug nuts to specification in a star pattern. Fully lower the vehicle and remove jack stands.

Reassembly

1. All suspension fasteners must be torqued with the vehicle at ride height or with suspension loaded to simulate normal position
2. Always use a new cotter pin for the ball joint castle nut
3. Inspect all rubber bushings for proper seating and absence of binding during installation
4. Verify sway bar end link moves freely without binding after installation

Verification

• Bounce the front suspension several times to settle components and verify no unusual noises
• Verify all fasteners are fully tightened and cotter pin is properly installed
• Perform a visual inspection underneath the vehicle for any loose components or interference
• Test drive at low speed in a safe area to verify normal handling and no suspension noises
• Schedule a professional alignment as soon as possible, as radius arm replacement affects front suspension geometry

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