HOSE-RETURN 1073938 - Caterpillar

Impeller Clutch
The impeller clutch is used to change the torque output of the torque converter. The impeller clutch allows the operator to use the left service brake pedal to reduce wheel spin. The impeller clutch also allows the operator to use the left service brake pedal to provide more engine power for the hydraulic system.
Illustration 5 g01455024
Right Side Console (22) Reduced rimpull select switch.
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Left Side Front Dash (23) Reduced rimpull indicator lamp.Reduced rimpull select switch (22) is used to provide four levels of reduced rimpull. Reduced rimpull is enabled only when the transmission is in first speed forward.Reduced rimpull select switch (22) is located on the right hand console. In the HIGH position, the reduced rimpull switch commands maximum rimpull.Reduced rimpull select switch (22) works in order to change the torque output of the torque converter. The power train ECM increases the amount of current to the impeller clutch solenoid valve in order to reduce rimpull. The position of the reduced rimpull select switch regulates the amount of current that is sent to the impeller clutch solenoid valve.Reduced rimpull indicator lamp (23) is on when the transmission is in first speed forward and the select switch for reduced rimpull is not in the HIGH position. When the transmission is shifted to second speed, to third speed, or to reverse, the reduced rimpull indicator lamp will be off. Reduced rimpull is now disabled.
Illustration 7 g01455029
The impeller clutch modulates at each instance of a directional shift. The impeller clutch also absorbs energy during the directional shift. This reduces the amount of energy that is absorbed by the direction clutch, which results in an easier shift.The oil flow to the impeller clutch is controlled by the impeller clutch solenoid valve. The impeller clutch solenoid valve is positioned on the outer cover. The impeller clutch solenoid valve is activated by the power train ECM.The following conditions affect the operation of the impeller clutch:
The position of the left service brake pedal
Directional shifts and speed shifts
Direction of rotation of the torque converter output shaft and torque converter output speed
Position of the reduced rimpull select switchLeft Service Brake Pedal
The left service brake pedal controls the amount of brake pressure that is used to apply the service brakes. The left service 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 the NEUTRAL position.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 ten degrees of pedal travel. Depressing the left pedal past this point applies the service brakes.
Illustration 8 g00107064
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