Shift Solenoid: Description and Operation

SHIFT CONTROLS





The Hydra-matic 4T60-E uses two ON/OFF shift solenoid valves with a 2-port design that provides for all forward gear ranges. These shift solenoid valves work together in a combination of ON or OFF sequences to direct fluid pressures to the various shift valves and apply components. The following table shows the solenoid state for each gear range:

1-2 SHIFT SOLENOID VALVE





The PCM controls the ground for the 1-2 Shift Solenoid (1-2 SS) valve, thereby commanding the solenoid ON or OFF according to transmission and vehicle operation. When the solenoid is OFF, filtered line pressure that is fed to the solenoid will cease. When energized (ON), the exhaust port is blocked, stopping the exhaust of line pressure through the solenoid. Pressure on the end of the 1-2 shift solenoid valve moves the valve against a spring force, sending line pressure into the 1-2 shift solenoid fluid passage to the 3-4 shift valve.

2-3 SHIFT SOLENOID VALVE





The 2-3 Shift Solenoid (2-3 SS) valve functions identically to the 1-2 Shift Solenoid valve in that the PCM controls the ground to the solenoid, commanding it ON or OFF. When the solenoid is OFF, filtered line pressure feeding the solenoid will cease. When energized (ON), the exhaust port is blocked, stopping the exhaust of line pressure and directing it into the 2-3 shift solenoid fluid passage. The 2-3 shift solenoid fluid pressure then feeds to the 4-3 manual downshift valve and the 3-2 manual downshift valve.

TCC CONTROLS
Most Hydra-matic 4T60-E transaxle models also use two solenoid valves to control TCC apply and release. The first solenoid valve in this system is the pressure controlling solenoid. It is a Pulse Width Modulation (PWM) solenoid valve that acts as a direct bias on the converter clutch regulator valve. This solenoid valve is normally open.
The other solenoid valve is an ON/OFF solenoid valve with a 2-port design that is identical to the two shift solenoid valves. This type of system provides for accurate control of regulated apply pressure that feeds the apply side of the torque converter clutch plate.

TORQUE CONVERTER CLUTCH PULSE WIDTH MODULATION SOLENOID VALVE





The PCM controls the Torque Converter Clutch Pulse Width Modulation Solenoid valve (TCC PWM Sol valve) by varying its operating duty cycle (ON/OFF time) from 0% to 100%. Until the transmission is operating in 3rd gear, the TCC PWM Sol valve is OFF. In this state, filtered PWM feed pressure flows at maximum pressure through the solenoid and into the PWM circuit.
When the TCC PWM Sol valve is energized, the valve operates at 32 Hz (cycles per second) and from 0% to 100% duty cycle depending on vehicle operation. The TCC PWM Sol valve is enabled to modulate the amount of PWM feed pressure passing through the solenoid, sending it to the converter clutch regulator valve. At 0% duty cycle, the torque converter clutch applies at minimum capacity. At 100% duty cycle the clutch applies at maximum capacity.

TORQUE CONVERTER CLUTCH SOLENOID VALVE





The Torque Converter Clutch Solenoid valve (TCC Sol valve) is an ON/OFF solenoid that functions in the same manner as the 1-2 shift solenoid valve and the 2-3 shift solenoid valve. As with the shift solenoids, the PCM provides the ground to command the TCC Sol. valve ON or OFF. The only difference in operation is that ignition voltage is supplied through the normally closed brake switch to the solenoid.
When the solenoid is OFF, and if the transmission is operating in third or fourth gear, the TCC signal fluid exhausts through the solenoid. When energized (ON), the exhaust port is blocked. This allows the TCC signal fluid pressure to move the converter clutch valve against the spring force and the line pressure at the opposite end of the valve.