992K Wheel Loader and 854K Wheel Dozer Braking System Caterpillar

The left brake pedal controls the amount of brake oil pressure that is used to apply the service brakes. The left brake pedal also controls the amount of pressure that actuates the impeller clutch. The impeller clutch is positioned between the engine and the torque converter.

By using the left brake pedal, the operator may divert engine power to the implement hydraulic circuit without putting the transmission in NEUTRAL.

As the operator depresses the pedal, the impeller clutch pressure drops quickly to a working pressure. The pressure is then modulated to a reduced pressure. This sequence occurs during the next 10 degrees of pedal travel. Depressing the left brake pedal past this point applies the service brakes.

Illustration 1	g00103246
Typical torque converter impeller clutch (X) Approximate pedal position in degrees (Y) Approximate percent of impeller clutch pressure

Range (A) indicates the released position. In this range, the brake pedal does not apply the service brakes.

Range (B) indicates the first 2 degrees of pedal movement. In this range, the impeller clutch pressure is reduced to the maximum working pressure level. Range (B) is the approximate pressure range for preventing slippage of the impeller clutch.

Range (C) occurs approximately within the next 10 degrees of pedal travel. The impeller clutch pressure is modulated from the maximum working pressure to the minimum impeller clutch pressure.

Range (D) indicates the percent of service brake pressure.

Range (E) indicates the impeller clutch pressure.

Note: For more information about the torque converter impeller clutch, refer to Systems Operation, RENR8910, "992K Wheel Loader and 854K Wheel Dozer Power Train", "Torque Converter".