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| Illustration 1 | g01456042 |
Output side of the torque converter (1) Modulating valve for the torque converter lockup clutch. (2) Modulating valve for the impeller clutch. | |
The modulating valve for the torque converter lockup clutch is located on the output side of the torque converter. The valve is positioned just above the modulating valve for the impeller clutch.
The modulating valve for the torque converter lockup clutch basically controls the flow of oil to the torque converter lockup clutch. The modulating valve engages the lockup clutch. The valve also disengages the lockup clutch in response to a variety of operating conditions. The lockup clutch will provide better machine performance during load and carry applications. The lockup clutch also provides better performance during light to medium dozing.
The modulating valve for the torque converter lockup clutch is an output of the power train electronic control module (ECM). The ECM will analyze the proper control data. When the ECM determines that the conditions are correct, the ECM will energize the valve. Once the modulating valve has been energized, the lockup clutch is engaged. This allows the output shaft of the torque converter to turn at a speed that is consistent with the engine output. The engagement of the torque converter lockup clutch basically provides a direct transfer of power from the engine output to the torque converter output.
Operation of the lockup clutch can be affected by the following items:
- Lockup enable switch
- Transmission speed switch
- Transmission direction switch
- Torque converter output speed
- Engine speed
- The position of the left service brake pedal
The power train ECM has parameters that will enable the modulating valve. The modulating valve will then engage the lockup clutch. When the input speed of the transmission rises above 1500 RPM, the ECM will signal the modulating valve to engage the lockup clutch. The ECM also has parameters that will disengage the lockup clutch. If the input speed of the transmission falls below 1350 RPM, the ECM will signal the modulating valve to disengage the lockup clutch. There are other input conditions that may cause the ECM to signal the lockup clutch to disengage.
ReferenceFor information on calibrating the clutch solenoid modulating valves, refer to the service manual module Testing and Adjusting, "Calibration" of the machine that is being serviced.
ReferenceFor more information on the power train electronic control module (ECM), refer to the service manual module Systems Operation, "Electronic Control Module " of the machine that is being serviced.