12H Motor Grader 4ER00001-UP (MACHINE) POWERED BY 3306 Engine(SEBP2...

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Product: MOTOR GRADER

Model: 12H MOTOR GRADER 4ER
Configuration: 12H Motor Grader 4ER00001-UP (MACHINE) POWERED BY 3306 Engine

Systems Operation
120H, 12H, 135H, 140H, 143H, 160H and 163H Motor Graders Air System and
Brakes
Media Number -RENR1417-05 Publication Date -01/06/2007 Date Updated -06/06/2007

i01183791

Parking Brake
SMCS - 3077; 4267

Illustration 1 g00104943

(1) Parking brake. (2) Air inlet to parking brake. (3) Outer plug.

NOTICE

Care must be taken to ensure that fluids are contained during

performance of inspection, maintenance, testing, adjusting and repair
of the product. Be prepared to collect the fluid with suitable containers
before opening any compartment or disassembling any component
containing fluids.

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Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop

Products Guide" for tools and supplies suitable to collect and contain
fluids on Caterpillar products.

Dispose of all fluids according to local regulations and mandates.

Parking brake (1) is located on the transmission output shaft. The parking brake is spring engaged.
Air pressure releases the parking brake. The parking brake includes outer plug (3), which can be
removed in order to access the inner plug (not shown). When the outer plug is removed, the small
amount of oil should be drained into a suitable container. Remove the inner plug in order to drain
moisture from the machine air system.

Illustration 2 g00122826

(4) Transmission direction and speed control (lever) in the PARKING BRAKE ENGAGED position.

Air from the air control valve for the service brakes flows through the check valve for the parking
brake. When lever (4) is depressed and the lever is moved backward, pressure air flows through
the air control valve for the parking brake.

Then, air flows through a junction block and into parking brake (1) at air inlet (2), which is on the
transmission flange. This disengages the parking brake.

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Illustration 3 g00104947

(5) Plates. (6) Brake housing. (7) Dowel. (8) Hub. (9) Discs. (10) Transmission output shaft. (11) Piston. (12) Piston.
(13) Springs. (14) Air chamber. (15) Transmission cover.

The parking brake consists of several components. Hub (8) is connected to transmission output
shaft (10) and discs (9) are splined to hub (8). Plates (5) are held stationary by dowels (7), which
are inserted into transmission cover (15) and into brake housing (6). Brake housing (6) is bolted to
transmission cover (15). Piston (11) provides a passage for the necessary flow of air to air
chamber (14) in order to activate piston (12). This releases the parking brake when lever (4) is

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moved from the PARKING BRAKE ENGAGED position. Springs (13) provide clamping force
across the brake pack in order to engage the parking brake when air chamber (14) is
depressurized.

When lever (4) is in the PARKING BRAKE ENGAGED position, air pressure is not available to
air chamber (14). Springs (13) force piston (12) so that the piston contacts plates (5) and discs (9).
Piston (12) forces plates (5) and discs (9) against transmission cover (15). Springs (13) generate
enough force in order to create sufficient friction between plates (5) and discs (9) so that discs (9)
stop spinning. Since discs (9) are splined to hub (8) and the hub is connected to transmission
output shaft (10), the transmission output shaft does not turn. When lever (4) is in the PARKING
BRAKE ENGAGED position or air chamber (14) is depressurized, the machine cannot move.

When the machine is stopped and lever (4) is pushed into the PARKING BRAKE ENGAGED
position, the transmission remains in the NEUTRAL position.

When lever (4) is in the NEUTRAL position, in any of the FORWARD positions, or in any of the
REVERSE positions, the parking brake is in the OFF position and air is pressurized within air
chamber (14). Pressurized air then forces piston (12) against springs (13). The clamping force
across the brake pack is eliminated. Discs (9) are allowed to rotate freely with hub (8) and with
transmission output shaft (10).

NOTICE

Do not engage the parking brake while the machine is moving unless
the primary service brake fails. The use of the parking brake as a
service brake in regular operation will cause severe damage to the
parking brake system.

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