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| Illustration 1 | g00899881 |
Service and parking brake (1) Service brake piston (2) Service brake oil passage (3) Reaction plate (4) Disc (5) Reaction plate (6) Disc (7) Reaction plate (8) Parking brake oil passage (9) Parking brake piston (10) Axle (11) Spring (12) Hub assembly (13) Pin (14) Spring (15) Spring | |
The service and parking brakes are an oil immersed, dual disc type brake group and are located in each axle housing on both sides of the differential. Each brake group consists of a service brake piston and a parking brake piston. The service brakes are hydraulically applied and spring released. The parking brakes are engaged by springs and disengaged by hydraulic oil pressure.
The heat created from the friction of the brakes is removed by the oil in the axle housing.
Service brake piston (1) and reaction plates (3), (5) and (7) are held stationary by three pins (13) installed in the differential and axle housings. Springs (14) and (15) keep reaction plates (3), (5) and (7) and discs (4) and (6) separated when the brakes are released.
Spring (14) holds reaction plate (3) against service brake piston (1) and also pushes the piston to the retracted position when the service brakes are released. Spring (15) holds reaction plate (7) against parking brake piston (9) .
Springs (11) keep parking brake piston (9) in the engaged position.
Discs (4) and (6) are connected by splines to hub assembly (12). Hub assembly (12) is connected by splines to axle (10). Discs (4) and (6) and hub assembly (12) rotate with axle (10) .
When the parking brake is disengaged, oil pressure from the parking brake control valve flows through passage (8) in the axle housing. The pressure of the oil moves parking brake piston (9), compressing springs (11), until the parking brake piston contacts the end plate. Discs (4) and (6) and axle (10) are free to rotate.
When the parking brake is engaged, the oil behind parking brake piston (9) flows from passage (8) through the parking brake control valve and back to the hydraulic tank. With no oil pressure behind the parking brake piston, the force of springs (11) pushes parking brake piston (9), reaction plates (3), (5) and (7) and discs (6) and (4) against service brake piston (1). The friction between the reaction plates and the discs prevent discs (4) and (6) and axle (10) from rotating. The parking brake is engaged.
When either service brake pedal is pushed, brake oil flows from the service brake control valve through passage (2). The oil pressure to the service brakes is controlled by the service brake control valve. The force of oil behind service brake piston (1) moves the service brake piston against the force of springs (14) and (15) and pushes reaction plates (3), (5) and (7) and discs (6) and (4) against parking brake piston (9). The friction between the reaction plates, the discs and the pistons cause discs (4) and (6) and axle (10) to turn slower or stop.
When the brake pedal is released, the oil behind service brake piston (1) flows from passage (2) through the service brake control valve back to the hydraulic tank. With no oil pressure behind the service brake piston, springs (14) and (15) keep reaction plates (3), (5) and (7) and discs (6) and (4) separated to allow discs (4) and (6) and axle (10) to rotate. The service brake is released.