The transmission clutch solenoid modulating valves are mounted on the top of the transmission under the cab. There is o ne modulating valve for each of the th e six transmission clutches. The modulating valves are outputs of the power train electronic control module (ECM). The transmission clutch solenoid modulating valves are proportional solenoid valves. Th e modulating valves are used by the power p ower train ECM to directly modulate the oil pressure that is sent to each individual clutch. When the operator selects a direction or when the operator selects a speed the
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ECM sends the maximum current to the modulating valve, the oil pressure in the clutch is at the maximum. When no current is sent to the modulating valve, the oil pressure in the clutch is at the minimum. The power train ECM will activate the modulating valves that are selected by the operator. Modulating valves (1) and (2) supply oil to the direction clutches. Modulating valves (3), (4), (5) and (6) supply oil to the speed clutches. In order for the machine to move, one speed clutch solenoid and one direction clutch solenoid must be energized. When the transmission is in neutral, only one modulating valve (3) is energized. When the transmission is shifted to neutral, the direction clutch solenoid is de-energized and the present speed clutch solenoid is energized. The modulating valves have a connector with two contacts. One contact receives power from the corresponding connector contact of the power pow er train ECM (J1-48, J1-49, J1-51, J1-62, J1-65 and J1-66). The other contact of all the modulating valves join together. The contacts return power to connector contact J1-50, J1-55, and J1-60 of the power train ECM. Note: The solenoid coils are not designed to be operated at 24 DCV directly. The power train ECM sends a 24 volt PWM signal at a duty cycle which provides an average voltage of about 12 volts to the solenoid coils. Do not energize the solenoid coils with 24 DCV (+battery). The life of the solenoid coils will be drastically reduced if the solenoid coils are energized with 24 DCV D CV (+battery). If the solenoid coils must be energized by a sou rce that is different from the power train ECM, use 12 DCV to energize the solenoid coils. Reference: For information on troubleshooting the transmission, refer to the Service Manual module for Testing and Adjusting, "Power Train Troubleshooting" for the machine that is being serviced. Reference: For information on calibrating the modulating valves, refer to the Service Manual module for Testing and Adjusting, "Calibration and P rogramming" for the machine that is being bein g serviced. Reference: For information on calibrating the modulating valves, refer to the Service Manual module for Testing and Adjusting, "Fill Time for the Transmission Clutch - Calibrate" for the machine that is being serviced. Reference: For more information on the power train electronic control module (ECM), refer to the Service Manual module for Systems Operation, "Electronic Control Module (Power Train)"
