Electronic Governor Components

Governor pressure is developed and controlled electronically in the 42RE transmission. Components used for development and control of governor pressure include:

- governor body
- new design valve body transfer plate
- governor pressure solenoid valve
- governor pressure transducer
- transmission fluid temperature thermistor
- Transmission Speed Sensor
- Throttle Position Sensor
- Transmission Control Module (TCM)

VALVE BODY TRANSFER PLATE
A new transfer plate is used with the 42RE valve body. The transfer plate is designed to supply transmission line pressure to the governor body, which bolts to the lower side of the transfer plate.

GOVERNOR PRESSURE SOLENOID VALVE
The solenoid valve generates the governor pressure needed for upshifts and downshifts. It is an electro-hydraulic device and is located in the governor body on the valve body transfer plate.

The inlet side of the solenoid valve is exposed to normal transmission line pressure. The outlet side of the valve leads to the valve body governor circuit.

The solenoid regulates line pressure to produce governor pressure. The average current supplied to the solenoid controls governor pressure. One amp current produces zero kPa/psi governor pressure. Zero amps sets the governor-to-line pressure.

The TCM supplies electrical power to the solenoid valve. Operating voltage is 12 volts and is provided through the battery terminal on the module.

The solenoid is polarity sensitive. The module energizes the solenoid by grounding it through the signal ground terminal on the TCM.

GOVERNOR PRESSURE SENSOR
The governor pressure sensor measures Output pressure of the governor pressure solenoid valve. The sensor output signal provides the necessary feedback to the transmission control module. This feedback is needed to adequately control governor pressure.

TRANSMISSION FLUID TEMPERATURE THERMISTOR
Transmission fluid temperature readings are supplied to the transmission control module by the thermistor. The temperature readings are used to control engagement of the fourth gear overdrive clutch, the converter clutch, and governor pressure.

The TCM prevents engagement of the converter clutch and overdrive clutch when fluid temperature is below approximately 100 (30°F). If fluid temperature exceeds 126°C (260°F), the TCM will cause a 4-3 downshift and engage the converter clutch. The "OD Off" lamp in the instrument panel also illuminates when the shift back to third occurs. The transmission will not allow fourth gear operation until fluid temperature decreases to approximately 110°C (230°F).

The thermistor is mounted on the underside of the converter clutch solenoid. It is immersed in transmission fluid at all times.

OUTPUT SHAFT SPEED SENSOR
The transmission output shaft speed sensor is located in the overdrive unit. The sensor is positioned over the park gear. Sensor signals are triggered by the lugs on the park gear. Input signals from the sensor are sent to the transmission control module.

The vehicle speed sensor also serves as backup to the transmission speed sensor. Signals from this sensor are shared with the powertrain control module.

THROTTLE POSITION SENSOR (TPS)
The TPS provides throttle position input signals to both the transmission control module and powertrain controller. This input signal is used to determine the overdrive and converter clutch shift schedule and to select the proper governor curve.

TRANSMISSION CONTROL MODULE (TCM)
The TCM controls operation of the converter clutch, overdrive clutch, and governor pressure solenoid. The TCM determines transmission shift points based on input signals from the transmission thermistor, transmission speed sensor, engine speed sensor, vehicle speed sensor, and throttle position sensor.