Hubs, bearings, brakes and suspension

Before you start

These procedures are written for a technician with the tools and training to work on trailer running gear. If you are not sure of a step, stop and call Teddy at (254) 688-0806.

Tools

Jack and stands, wheel chocks, torque wrench, grease gun, brake adjusting tool, seal driver or a flat block, soft-faced hammer, brass drift, solvent and lint-free rags, multimeter and ammeter for electric brakes, dial indicator for end play and drum runout.

Removing a hub

1. Lift and support the trailer, then take off the wheel.
2. Pry or tap the grease cap off evenly around its edge. On oil-bath hubs, set a pan underneath, unscrew the cap and let the oil drain.
3. Straighten and pull the cotter pin. If the nut is held by a snap-on retainer or a tang washer instead, release that.
4. Unscrew the spindle nut and take off the spindle washer.
5. Pull the hub straight off the spindle. Keep a hand over the outer bearing so it does not fall. If the drum hangs up on the shoes, back off the brake adjuster first.
6. Lay the hub face down. From the front, tap the inner bearing and seal out with a wood dowel or brass drift. The seal is not reused.

Inspecting bearings and races

1. Wash the bearings and the inside of the hub in clean solvent and let them dry. Do not spin a dry bearing with compressed air.
2. Turn each bearing slowly by hand and look at every roller and the cage.
3. Look at both races in the hub and at the spindle journals and the seal surface.

To change a race, drive the old one out from behind with a brass drift, working around its edge. Clean the bore, then drive the new race in squarely until it seats against the shoulder all the way round.

Inspecting the drum

The drum has two working surfaces: the bore the shoes press on, and on electric brakes the flat inner face the magnet rides on.

Replacing the seal

1. Pack and fit the inner bearing first (next section).
2. Wipe the seal bore clean. Put a thin film of sealant on the outside of the new seal if it has a bare metal case.
3. Set the seal in the bore with its lip facing the bearing and drive it in with a seal driver or a flat block until it is flush. It must sit square, within 0.010 in all the way round.
4. Smear grease on the seal lip before the hub goes back on.

Packing bearings and fitting the hub

1. Work grease into each bearing from the wide end until it comes out between the rollers at the narrow end, all the way round. A bearing packer does this fastest. Coating the outside is not enough.
2. Put a light coat of grease on both races and on the spindle.
3. Set the inner bearing in its race and fit the new seal.
4. Slide the hub onto the spindle, taking care not to drag the seal lip across the threads.
5. Fit the outer bearing, the spindle washer and the nut.
6. Adjust the bearings as described next.

Grease: lithium complex, NLGI No. 2, extreme pressure, dropping point 419 °F (215 °C) or higher. Do not mix grease types.

Adjusting the bearings

For hubs held by a castle nut and cotter pin:

1. Turn the hub slowly while tightening the spindle nut to about 50 ft-lb. This seats the bearings.
2. Loosen the nut to take the torque off, without turning the hub.
3. Tighten the nut by hand until it is just snug.
4. Back the nut off to the first slot that lines up with the cotter pin hole and fit a new cotter pin. Bend the legs over.
5. The nut should be free to move slightly against the pin, and the hub should turn smoothly with barely perceptible end play, 0.001 to 0.005 in on a dial indicator.
6. Fit the grease cap. On hubs greased through the spindle, pump in grease until it shows at the front and fit the rubber plug.

Hubs held by two nuts and a lock washer

Heavier axles hold the hub with an inner nut, a lock washer and an outer nut instead of a castle nut.

1. Turn the hub while tightening the inner nut to 100 ft-lb.
2. Loosen the nut to take the torque off, without turning the hub, then tighten it by hand until snug.
3. Back the inner nut off 1/4 to 3/8 turn, fit the lock washer, and torque the outer nut to 100 to 175 ft-lb. Bend a tab of the washer over the outer nut where the design has one.
4. Check the end play with a dial indicator: 0.001 to 0.010 in.

Oil-bath hubs

1. Inspect and fit the bearings and seal as above, using oil instead of grease to coat the bearings on assembly.
2. Adjust the bearings, then fit the oil cap with its O-ring or gasket in good condition.
3. Fill through the plug with SAE 80W-90 hypoid gear oil to the level line. Give the oil a few minutes to work through the bearings, then top up.
4. Check for leaks at the seal and the cap after the first run.

Electric brake service

Inspection

Replace shoes as an axle set, and magnets in pairs. A new magnet needs a flat drum face to bed against, so reface or replace the drum at the same time. After new shoes or magnets, burnish the brakes: 20 to 30 stops from about 40 mph to 20 mph with cooling time between.

Lubrication

Put a thin film of high-temperature brake grease or anti-seize on the anchor pin, the actuating arm pivot, the adjuster threads, and the raised pads on the backing plate where the shoes rest. Keep all lubricant off the linings, the drum and the magnet face.

Mounting

The brake bolts to the flange on the spindle. Left and right brakes are not the same: the magnet's actuating arm must sweep in the direction of forward rotation. Torque the mounting nuts to the value for the stud size (not yet set; Teddy to supply).

Manual adjustment

Turn the star wheel through the slot in the backing plate until the wheel is hard to turn, then back it off until the wheel turns with a light drag. Set every brake the same. Self-adjusting brakes take up wear as the trailer is used and are only adjusted by hand after new shoes are fitted.

Electrical checks

Voltage

With the tow vehicle running and the trailer connected, measure across the two magnet leads at a brake while a helper works the controller. The reading should climb smoothly from zero to about 12 volts as the controller is applied. A reading that starts above about 2 volts makes the brakes grab.

Current

Put an ammeter in series with the brake feed wire and apply the controller fully.

Low current points to a poor connection, a bad ground or a wire that is too light. A reading well above the table points to a shorted magnet. No current points to an open circuit.

Wire size for the brake circuit

The two leads on a magnet are interchangeable: one goes to the brake feed and one to ground. Run a ground wire back to the connector. Do not rely on the trailer frame or the hitch ball as the ground path.

Hydraulic brake service

• Wheel cylinders. Pull back the boots and look for fluid. A wet cylinder or a seized piston means replace or rebuild it. Keep brake fluid off the linings; linings that have soaked up fluid are replaced.
• Lines and hoses. Replace any line that is kinked, corroded or leaking and any hose that is cracked, swollen or chafed. Clip lines so they cannot rub on the axle or frame.
• Shoes, drums and hardware. Inspect to the same limits as electric brakes.
• Adjustment. Manual-adjust brakes are set with the star wheel in the same way as electric brakes.
• Bleeding. After any line has been opened, bleed the system starting at the wheel farthest from the actuator, using the fluid named on the master cylinder cap. Do not reuse fluid.
• Free-backing brakes. These release when the drum turns backward. Fit them on the correct side; a free-backing brake on the wrong side will not hold going forward.

Leaf-spring suspension service

Support the trailer on its frame so the springs hang free before taking any suspension bolt out.

• Springs. Replace a spring that is cracked, has a broken leaf, or has sagged. Replace both springs on an axle together so the trailer sits level.
• Bushings and bolts. Replace bushings that are worn through or loose in the eye, and bolts with visible wear or damaged threads. Fit new locking nuts.
• Hangers, shackles and equalizers. Replace any part with an elongated hole, a crack or a bend. Check hanger welds for cracks.
• U-bolts and tie plates. Replace U-bolts that have been removed more than once, are stretched, or have damaged threads. Tighten the nuts evenly, a little at a time on each leg, so the tie plate pulls down flat.

Torsion axle service

The housing, rubber cords, inner bar and arm are assembled at the factory and are not serviced separately. The hubs, bearings, seals and brakes are serviced exactly as on a spring axle.

• Check the bracket-to-frame bolts with a torque wrench.
• With the trailer level and unloaded, compare the two arms. They should sit at the same angle.
• Look for cracks at the bracket welds and at the arm, and for rubber pushing out of the end of the housing.