980H Wheel Loader Service Brake Control Caterpillar

Illustration 1	g00904188

Right Service Brake Pedal

The right service brake pedal is used to slow down the machine's ground speed when the operator does not wish to have the transmission downshift.

The right service brake pedal is normally used for braking when the autoshift transmission control is downshifting adequately.

Left Brake Pedal

The left service brake pedal provides three braking functions:

• Automatic Downshifting of the Transmission

• Neutralization of the Transmission

• Conventional Braking

The left brake pedal is used to initiate automatic downshifting of the transmission at higher ground speeds.

When the left service brake pedal is depressed beyond a certain point, automatic downshifting and neutralization of the transmission will occur for all positions of the autoshift switch. The automatic downshifting and the neutralizing of the transmission saves wear on the service brakes, axles, and components of the power train.

Use the left brake pedal for most conditions when adequate traction is available.

Left Brake Pedal Operation

The functions of the left brake pedal depend on the position of the left brake pedal and on the position of the autoshift switch.

Illustration 2	g00904123
(A) Initial Travel (B) Downshifting and Service Brake Application (C) Additional Travel (application of service brakes) (1) Calibrated Initial Brake Pressure Point (2) Set Point for Neutralization (3) Pedal Position for Stopping the Machine (4) Maximum Pedal Travel (full application of service brakes)

Initial travel (A) of the left brake pedal will cause the transmission to downshift. The transmission will downshift to the lowest available speed. The lowest available speed depends on the position of the autoshift switch. Refer to Table 2 for the lowest available speed. Each downshift of the transmission will reduce the speed of the machine. The transmission will downshift at higher speeds than the normal automatic downshift speeds. The transmission will only downshift if an engine overspeed will not occur. The transmission will not upshift until the left brake pedal is fully released.

The transmission will be engaged again after the left brake pedal is released 4 degrees from maximum pedal position (3) . This will only happen if the transmission was neutralized. The service brakes will still be applied. This will allow the transmission to be engaged when the brakes are applied. This will help to prevent unwanted movement while you are on a slope.

Note: You should wait at least one second after releasing the left brake pedal to 4 degrees before completely releasing the pedal. This will allow the transmission to fully engage.

Depressing the left pedal will neutralize the transmission again.

Note: The left brake pedal requires calibration if the pedal was replaced. The neutralization of the transmission can also be adjusted.

ReferenceFor more information on calibration of the left brake pedal, refer to Power Train Testing and Adjusting, "Position Sensor (Left Brake Pedal) Calibrate".

Modes of Operation

Illustration 3	g00904125
Autoshift Switch

When the left brake pedal is fully released, the transmission will return to normal operation. The transmission will remain in the current speed if the autoshift switch is in MANUAL (1) .