Transmission Control

Note: The following automatic transmission components do not apply to all 4L60 transmissions. For information regarding your specific 4L60 model, see Transmission System Identification. To identify the specific type of 4L60, see wiring diagrams.

Typical 4L60 Electronic System:

Transmission Temperature Switch
Purpose:
The temperature switch allows the ECM/PCM to lock the Torque Converter Clutch (TCC). The application of the TCC makes a positive mechanical link between the crankshaft and transmission input shaft. Under less hydraulic stress, the hydraulic fluid can circulate and cool.

Operation:
The transmission must be in fourth gear for the temperature switch to apply [1][2]Torque Converter Clutch to cool the transmission fluid. The temperature switch is normally open. As the temperature increases the bi-metal switches, allowing the ECM/PCM to control the TCC solenoid. The temperature switch locks at about 155°C (279°F) and unlocks at about 143°C (259°F).

Location:
The temperature switch is located inside the transmission.


2nd Gear Switch
Purpose:
The second gear switch signals the ECM/PCM to adjust ignition timing based on transmission shift points. Adjusting ignition timing after a transmission shift, allows for higher shift speeds.

Operation:
The second gear switch is normally closed. As the transmission shifts into second gear, hydraulic pressure opens the switch.

Location:
The second gear switch is located inside the transmission.


3rd Gear Switch
Purpose:
The third gear switch signals the ECM/PCM to adjust ignition timing based on transmission shift points. Adjusting ignition timing after a transmission shift, allows for higher shift speeds.

Operation:
The third gear switch is normally closed. As the transmission shifts into third gear, hydraulic pressure opens the switch.

Location:
The third gear switch is located inside the transmission.


4th Gear Switch
Purpose:
This switch is used by the ECM/PCM to modify [1][2]Torque Converter Clutch lock and unlock points during a 4 - 3 gear downshift maneuver.

Operation:
The fourth gear switch is normally open and closes when the transmission shifts into fourth gear. This switch is hydraulically controlled.

Location:
The fourth gear switch is located inside the transmission.