Usage:
Start By:
a. remove rear wheel bearings and Duo-Cone seals*
* This operation is in the 793B Truck Power Train, Disassembly And Assembly Manual.
1. Drain the oil from the rear brake assembly.
2. Disconnect hose assembly (2) from the brake assembly.
3. Remove the bolts that hold tube assemblies (1) and (3) to the brake assembly. Remove the O-ring seal from the tube assemblies.
4. Mark for identification and disconnect the remaining hose assemblies from the brake assembly.
Typical Example
5. Fasten a hoist and tooling (A) to brake assembly (4).
6. Remove nuts (5) and (6) and the washers. Remove brake assembly (4) from the hub. The weight of the brake assembly is approximately 850 kg (1875 lb).
7. Remove the O-ring seal from the hub.
Install Rear Service And Parking Brakes
1. Put the O-ring seal in position on the hub. Put clean oil on the O-ring seal.
2. Fasten a hoist and tooling (A) to brake assembly (4). Put the brake assembly in position on the hub.
3. Install washers and nuts (5) and (6). Tighten forty seven inner nuts (5) to a torque of 880 ± 80 N·m (645 ± 60 lb ft). Tighten twenty one outer nuts (6) to a torque of 1170 ± 40 N·m (855 ± 30 lb ft).
4. Put the O-ring seals in position in tube assemblies (1) and (3).
5. Put tube assemblies (1) and (3) in position on the brake assembly, and install the bolts.
6. Connect hose assembly (2) to the brake assembly.
7. Identify and connect the remaining hoses to the brake assembly.
8. Fill the brake system with oil to the correct level. See the Operation & Maintenance Manual.
| NOTICE |
|---|
After installation of the rear wheel bearings and Duo-Cone seals, bleed the air from the brake system. See The Systems Operations/Testings & Adjusting and the topic "Remove Air From The Hydraulic Brake System (Bleed The Brakes) for the correct procedure. |
End By:
a. install rear wheel bearings and Duo-Cone seals*
* This operation is in the 793B Truck Power Train, Disassembly And Assembly Manual.
Disassemble Front Or Rear Service And Parking Brakes
The photos are from a 789 Truck rear service and parking brake. The procedure is the same for the 793B Truck.
Start By:
a. remove the front or rear service and parking brake
Typical Example
1. Put the brake assembly on blocks with the anchor up as shown.
2. Remove bolts (1) and the washers that hold the anchor in place.
3. Loosen nuts (2) one half of one turn at a time to release the compression spring tension.
4. Fasten a hoist and tooling (A) to anchor (3), and remove the anchor from the brake assembly. The weight of the anchor is approximately 403 kg (888 lb).
5. Remove nuts (2) from the anchor.
6. Turn anchor assembly (3) over the service brake piston facing up as shown.
7. Install two 3/8" - 16 NC forcing screws (5) in service brake piston (4). Tighten the forcing screws evenly to compress the guide springs.
8. Use needle nose pliers, and install cotter pin (7) in guides (6) to hold them in place when the forcing screws are removed.
9. Remove forcing screws (5) from the service brake piston.
10. Use a soft hammer to push service brake piston (4) down, and remove pins (8) from guides (6).
11. Fasten a hoist and two 3/8" - 16 NC forged eyebolts (9) to service brake piston (4). Remove the piston from the anchor. The weight of the service brake piston is 85 kg (187 lb).
12. Remove two seals (10) and two seals (11) from service brake piston (4).
13. Loosen nuts (12) one half to one turn at a time to release the compression spring tension.
14. Fasten a hoist and two 3/8" - 16 NC forged eyebolts to parking brake piston (14). Remove the parking brake piston and housing (13) from the brake assembly. The weight of the parking brake piston and housing is 112 kg (247 lb).
15. Remove nuts (12) from housing (13).
16. Put the parking brake piston and housing (13) in position on tooling (B), and separate the housing and parking brake piston (14).
17. Remove two seals (15) and two seals (16) from housing (13).
18. Remove seal (17) from the parking brake piston.
19. Use tool (C) to compress the guide spring. Remove cotter pin (7), guide (6) and the guide spring from the parking brake piston.
20. Remove two O-ring seals (18) from anchor (3).
NOTE: There are four springs (19) at location (X) which do not have inner springs. Put identification marks on the springs for correct installation during assembly.
21. Remove 46 springs (19) and 42 inner springs (20) from the anchor.
22. Remove damper assembly (21) from the ring.
23. Fasten a hoist to tub (23), and remove the hub. The weight of the hub is 77 kg (170 lb) for the rear service brake. The weight of the hub is 64 kg (141 lb) for the front service brake. Remove discs (24), plates (22) and the damper assembly from the brake assembly.
Typical Example
24. Fasten a hoist to the plate and ring assembly, and turn plate and ring assembly over. The weight of the plate and ring assembly is approximately 275 kg (600 lb). Remove bolts (26).
25. Fasten a hoist to plate (25) and remove the plate from the ring. The weight of the plate is approximately 125 kg (275 lb).
Typical Example
26. Remove O-ring seal (28) from ring (27).
Assemble Front Or Rear Service And Parking Brakes
NOTE: Put clean oil on all seals and metal surfaces before they are assembled. Make sure the seals are not broken or damaged and metal surfaces are not scratched or worn.
Typical Example
1. Put O-ring seal (28) in position in the groove in ring (27).
Typical Example
2. Put plate (25) in position on the ring, and install bolts (26) that hold it in place. Tighten the bolts to a torque of 500 ± 50 N·m (370 ± 37 lb ft).
3. Put hub (23) in position in the brake assembly.
NOTE: The damper assembly must be installed with the facing material facing down toward the plate.
4. Put the damper assembly in position on the plate.
| NOTICE |
|---|
Oil discs (24) at assembly with clean 10W Transmission Oil. |
5. Start with a disc, and alternate discs and plates until discs (24) and plates (22) have been installed.
NOTE: Damper assembly (21) must be installed with the facing material facing up toward the service brake piston.
6. Put damper assembly (21) in position in the brake assembly.
7. Put two O-ring seals (18) in position in the grooves in anchor (3).
NOTE: Make sure the springs at locations (X) do not have inner spring installed in them.
8. Install 46 outer springs (19) and 42 inner springs (20) in the anchor. Do not install an inner spring in the four springs in locations (X).
NOTE: The yellow stained side of seals (15) and (16) must be facing out.
9. Install two seals (16) and two seals (15) in the grooves in housing (13).
10. Align the notches for the nuts in housing (13) with the holes in the parking brake piston, and install the housing.
11. Put O-ring seal (17) in position in the groove in the parking brake housing.
12. Put the guide spring and guide (6) in position in the parking brake housing. Use tool (C) to compress the guide spring, and install cotter pin (7) in guide (6).
13. Put nuts (12) in position on housing (13).
14. Fasten a hoist and two 3/8" - 16 NC forged eyebolts to parking brake piston (14). Align the guides with the four outer springs that do not have inner springs in them, and install the parking brake piston.
15. Tighten nuts (12) one turn at a time to pull the housing down evenly. After the nuts have been installed, tighten the nuts to a torque of 270 ± 25 N·m (200 ± 18 lb ft) in a criss cross pattern.
16. Put two seals (11) and two seals (10) in position in the groove in service brake piston (4).
17. Fasten a hoist and two 3/8" - 16 NC forged eyebolts (9) to service brake piston (4). Align the four holes in the piston with the guides, and install service brake piston (4).
18. Use a soft hammer to push service brake piston (4) down, and install pin (8) in guide (6).
19. Install two 3/8" - 16 NC forcing screws (5) in the service brake piston. Tighten the forcing screws evenly to compress the guide springs, and remove cotter pin (7) with a pair of needle nose pliers. Remove the forcing screws.
20. Fasten a hoist and tooling (A) to anchor (3) as shown.
21. Put nuts (2) in position on the anchor.
22. Align the anchor with the brake assembly, and lower the anchor (3) into position.
23. Tighten nuts (2) one turn at a time to pull the anchor down evenly. After the nuts have been installed, tighten them to a torque of 270 ± 25 N·m (200 ± 18 lb ft).
24. Install bolts (1). Tighten the bolts to a torque of 500 ± 50 N·m (370 ± 37 lb ft).
End By:
a. install the front or rear service and parking brake