The radius arm aft bushings carry every braking, accelerating, and trail-impact load on the TTB front end — when they crack, the front beam walks under load and the truck wanders. Plan for a 2-4 hour driveway job and torque the aft nut to 80-120 ft-lbs on poly, never higher.
Each TTB beam is held fore-aft by a single radius arm that bolts to the front of the beam and runs back to a frame bracket. The aft mount is two halves of a tall bushing pressed around the arm's threaded stud. As those bushings age, they crack, then split, then disappear — and the front axle starts moving fore-and-aft under load. The truck darts under braking, wanders on the freeway, and clunks when you hit the gas. Replacement bushings cost $40-90 and the job is well within a driveway DIY budget if you have a torque wrench that reaches 320 ft-lbs for the axle-end bolt.
Start by lifting the front, supporting the frame on stands, and dropping the axles into full droop. Penetrate the radius arm aft nut and the front axle-to-arm bolt with PB Blaster the night before — these are 25-40 year old fasteners and they will fight you. The aft nut takes a 1-1/16 socket. The axle-end bolt is the larger fastener and takes a breaker bar and a long cheater for first crack. Don't try to do this with a 1/2" ratchet.
Once the aft nut is off, the upper bushing half pulls out by hand. Slide the radius arm forward out of the frame bracket, drop the lower bushing half out, and inspect the arm's threaded stud. If the threads are damaged, this is the moment to chase them. If the stud is bent, replace the radius arm — typically $80 used in a wrecking yard. Don't shim or pack a worn arm; the bushings will fail again immediately.
Install the new bushings according to the kit instructions. Poly kits like the Energy 4.7125G include a small tube of poly grease — use it. Poly without grease will squeak forever. Slide the arm back into place, install the upper bushing half and the cone washer, and start the aft nut by hand. Re-install the axle-end bolt and torque to 320-340 ft-lbs. Then torque the aft nut: 80-120 ft-lbs for rubber, 80-100 ft-lbs for poly. Crushing poly bushings past 100 ft-lbs is the most common rookie error — it ruins them in a single drive.
| Part | Vendor | Est. price |
|---|---|---|
| James Duff radius arm bushings — 2WD/4WD set | James Duff Inc. | ~$75 |
| Energy Suspension polyurethane radius arm bushings | Summit Racing / Amazon | ~$55 |
| OEM rubber radius arm bushings — pair | Rock Auto / NAPA | ~$38 |
| Radius arm aft nut | hardware store / dealer | ~$4 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.