How do I replace the electric brakes on a fifth wheel?
Diagnose first
A fifth wheel with weak or grabbing brakes is often electrical rather than worn out. Before buying assemblies, check the controller gain, clean the 7-pin plug and its ground pin, and read the magnet resistance at each wheel with the drum off: a reading near zero is a shorted coil, open is a broken one, and a left-right mismatch explains a pull. Our weak or grabbing brakes guide walks through it in order. Replace when the shoes are worn or grease-soaked, a magnet is worn through or grooved, or springs and hardware are broken.
Buy complete assemblies, matched to the axle
Electric brakes are usually replaced as complete backing-plate assemblies, with shoes, magnet, springs and adjuster already built in, rather than rebuilt piece by piece. Match four things before ordering:
- Drum size and axle rating. Ten-inch brakes go with 3,500 lb axles; twelve-inch with 5,200 to 7,000 lb. Read the axle plate or measure across the drum.
- Flange bolt pattern on the axle behind the hub.
- Side. Assemblies are handed; left and right differ.
- Quantity. Replace by the axle so braking stays balanced. On a multi-axle fifth wheel, inspect every wheel while you are at it.
The job, wheel by wheel
- Chock, jack at a proper point and support the frame on rated stands.
- Remove the wheel, dust cap, cotter pin, spindle nut and washer, then slide the hub off. Catch the outer bearing.
- Inspect the bearings, races and seal. Grease inside the drum means the seal failed; fix that or it will soak the new shoes.
- Note the two magnet wires and their routing, then disconnect them.
- Unbolt the old assembly from the flange and fit the new one on the correct side, tightened to the axle or brake maker's specification.
- Reconnect with sealed, protected connectors. Poor splices are a common cause of weak or intermittent brakes.
- Refit the hub with packed bearings and a new seal, set the preload, and fit a new cotter pin.
- Adjust the star wheel until the shoes drag, then back off until the wheel spins with a faint scrape.
- Torque the lugs in a star pattern and recheck after a short tow.
After the job
Load the trailer as you tow it, then on a quiet road raise the controller gain until the brakes just begin to lock on the manual override, and back off a step. Re-adjust the brakes after the first few hundred miles as the shoes bed in.
What we stock, plainly
The electric brake pair and brake drum hub we carry are Black Series OEM parts for HQ independent suspension axles, so we do not list them for a fifth wheel. For the fifth wheel we can supply the running gear around the brakes: genuine Timken kits (12-inch for 5,200 to 7,000 lb axles, 10-inch for 3,500 lb), cotter pins, a 7-way plug cord with junction box, and a CURT breakaway kit. Read the number stamped on your old bearing cones to confirm the kit. Everything ships from Upland, California.
What you need
Want the full walkthrough? Read the complete guide.