Removal Procedure
- Block the wheels.
- Drain all air reservoirs. Refer to Draining Reservoirs in Air Brakes.
- Cage the rear air brake chambers. Refer to Caging the Rear Air Brake Chamber .
- Raise the vehicle and support the vehicle with safety stands. Refer to Lifting and Jacking the Vehicle in General Information.
- Remove the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
- Remove the brake drums. Refer to Brake Drum Replacement .
- Push down on the bottom brake shoe.
- Pull on the brake shoe roll retainer in order to remove the bottom brake shoe roller.
- Lift the bottom brake shoe in order to release the tension on the brake shoe return spring.
- Remove the brake shoe return spring.
- Rotate the bottom brake shoe in order to release the tension on the two retaining springs.
- Remove the retaining springs.
- Remove the brake shoes.
- Inspect the brake spider (4) for expanded anchor pin holes and for cracks.
- Inspect the brake chamber/camshaft support bracket (8) for the following conditions:
- Replace damaged brake chamber/camshaft support brackets (8).
- Inspect the anchor pins (14) for corrosion and wear.
- Inspect the camshaft (12) for the following conditions:
- Replace damaged camshafts (12).
- Inspect the brake drums. Refer to Brake Drum Inspection .
- Measure the brake shoe anchor pin to the brake shoe roller hole span distance on the 419 mm (16.5 in) diameter brake shoes.
- Replace the brake shoe if the distance from the center of the brake shoe anchor pin slot to the center of the brake shoe roller slot is more than 325 mm (12.779 in).
- Measure the brake shoe anchor pin to the brake shoe roller hole span distance on the Rockwell 419 mm (16.5 in) diameter brake shoe.
- Replace the brake shoe if the brake shoe anchor pin hole diameter is more than 25.62 mm (1.009 in).
- Disassemble the brake lining (17) from the brake shoe.
- Drill out the rivets.
- Clean the burrs and the high spots from the brake shoe with a file.
- Clean the brake shoe and the brake lining contact surfaces.
Caution: Avoid taking the following actions when you service wheel brake parts:
• Do not grind brake linings. • Do not sand brake linings. • Do not clean wheel brake parts with a dry brush or with compressed air.
Replace damaged brake spiders (4) and the anchor pin bushings (15).
| • | Broken welds |
| • | Cracks |
| • | Misalignment |
Replace damaged anchor pins (14).
| • | Cracks |
| • | Wear |
| • | Corrosion |
Installation Procedure
- Install the primary brake lining on the primary brake shoe.
- Follow the rivet machine manufacturer's instructions.
- Assemble the new brake lining onto the brake shoe.
- Apply chassis lubricant to the anchor pins where the anchor pins touch the brake shoes.
- Apply lubricant to the brake shoe rollers where the brake shoe rollers touch the brake shoes. Use a chassis lubricant.
- Put the upper brake shoe in position on the top anchor pin.
- Hold the lower brake shoe on the bottom anchor pin.
- Install the two new brake shoe retaining springs.
- Rotate the lower brake shoe forward.
- Install the new brake shoe return spring.
- Install the open end of the return spring hooks toward the camshaft.
- Pull each brake shoe away from the camshaft in order to allow enough space for the brake shoe rollers and the brake shoe retainers.
- Press the ears of the brake shoe retainer together in order to allow the brake shoe retainer to fit between the brake shoe webs.
- Push the brake shoe retainer into the brake shoe web until the ears lock in the holes in the brake shoe webs.
- Install the brake drums. Refer to Brake Drum Replacement .
- Adjust the wheel bearings, if needed. Refer to Wheel Bearing Adjustment In Rear Drive Axle or Wheel Bearing Adjustment in Front Suspension.
- Install the tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
- Remove the safety stands and lower the vehicle.
- Start the engine.
- Charge the air system to the air compressor governor valve cut-out point.
- Stop the engine.
- Adjust the brakes. Refer to Air Drum Brake Adjustment .
- Uncage the rear air brake chambers. Refer to Caging the Rear Air Brake Chamber .
- Check for proper brake operation.
- Set the parking brake.
- Remove the wheel blocks.
The first brake shoe past the cam in the direction of the wheel rotation is the primary brake shoe. The primary and the secondary brake shoes may be in either position, depending on the location of the cam. If the cam is behind the axle, the top brake shoe is the primary brake shoe and the lower brake shoe is the secondary brake shoe. If the cam is in front of the axle, the lower brake shoe is the primary brake shoe.
The brake lining to the brake shoe gap at both ends and both sides must not exceed 0.25 mm (0.010 in).
The brake lining to the brake shoe gap between webs at both ends must not exceed 0.64 mm (0.025 in).
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Important: Do not get grease on the part of the brake shoe roller that touches the camshaft.
