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| Illustration 1 | g00734211 |
View of the Service Brake Pedals | |
All four of the service brakes are located in the axle assemblies. The service brakes are actuated by the left brake pedal or by the right brake pedal. There are service brakes in the front axle and in the rear axle.
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| Illustration 2 | g00734393 |
Service Brakes (1) Sun gear. (2) Piston. (3) Service brake oil passage. (4) Disc. (5) Plate. (6) Axle. (7) Carrier. (8) Pins (three). (9) Springs (three). (10) Ring gear. | |
Each service brake consists of the following components: piston (2), disc (4), plate (5), pins (8) and springs (9) .
Plate (5) and piston (2) are held stationary by three pins (8). The pins are fastened in the differential housing and in the axle housing. The piston and the plate are able to slide on the three pins. Springs (9) keep piston (2) in the retracted position when the piston is not being used.
The inside diameter of disc (4) has splines that fit on the splines of sun gear (1). This causes disc (4) to rotate at the speed of the sun gear.
Grooves are cut into the faces of disc (4). The grooves allow the passage of cooling oil even when the service brakes are applied. As the disc rotates, cooling oil will constantly flow between disc (4) and plate (5) and between piston (2) and disc (4) .
Carrier (7) is fastened to axle (6) by splines. The axle turns with the carrier. The gears in carrier (7) rotate between sun gear (1) and stationary ring gear (10) .
When you push a brake pedal, pressurized oil from the service brake control valve flows through oil passage (3) in the differential housing. The force of the oil behind piston (2) moves the piston against the force of springs (9) .
The force of the oil also pushes disc (4) against plate (5). This causes friction between disc (4) and piston (2) and between disc (4) and plate (5). The friction causes sun gear (1), axle (6), carrier (7) and the wheels to turn more slowly. If the operator does not release the brake pedal, the friction will eventually stop the wheels.
The heat that is created from the friction of the service brakes is removed by the oil that is in the axle housings.
When the brake pedal is released, the oil behind piston (2) flows through oil passage (3). This oil flows to the service brake control valve. The oil then returns to the hydraulic oil tank. With no oil pressure behind piston (2), springs (9) move the piston to the retracted position and the service brakes are released.
If the machine loses power or the hydraulic pump fails, the service brakes can still be applied. The pressure in the brake accumulators allows several applications of the brake pedals so that the machine can be slowed enough to engage the parking brake.
Transmission Neutralizer (Limit Switch)
Note: This section is for machines with the following serial numbers: (6XR1-18257SR1-11998CR1-20469AR1-599)
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| Illustration 3 | g00734162 |
The service brakes can be actuated by the left brake pedal or by the right brake pedal. This is also true for the function of the transmission neutralizer. When the service brakes are applied, 25 mm (1 inch) of pedal travel is required in order to actuate the limit switch (11). The limit switch must be actuated in order to neutralize the transmission.
Transmission Neutralizer (Pressure Switch)
Note: This section is for machines with the following serial numbers: (6XR1826-UP7SR1200-UP8CR2047-UP9AR600-UP)
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| Illustration 4 | g00734095 |
View of the pressure switches on the brake control valve | |
The service brakes can be actuated by the left brake pedal or by the right brake pedal. This is also true for the function of the transmission neutralizer. When the transmission neutralizer lockout switch is in the OFF position, both of the brake pedals will apply the service brakes. At the same time, the pressure switch on the rear axle causes the transmission to shift to NEUTRAL. This allows the full engine power to be used in the hydraulic system.
When the service brakes are applied, the pressure in the brake lines increases. When the pressure reaches 875 ± 103 kPa (127 ± 15 psi), the pressure switch for the rear brakes (13) sends a signal to the transmission in order to shift the transmission to NEUTRAL. All of the engine power will go to the hydraulic system. When the brake pedal is released, the pressure in the brake lines will decrease. When the pressure falls below 1325 ± 170 kPa (192 ± 25 psi), the pressure switch for the front brakes (12) sends a signal to the transmission in order to engage the transmission.
If the top of the transmission neutralizer override switch is pressed, the transmission will not shift to NEUTRAL when the service brakes are applied. This will result in increased wear on the brake discs.