As vehicle speed increases and operating conditions become appropriate, the transmission control module (TCM) processes input signals from the input and output speed sensors, the throttle position (TP) sensor and other vehicle sensors to determine the precise moment to command ON the normally low pressure control solenoid 2 trim to regulate 1-3 clutch apply. At the same time the normally high pressure control solenoid 3 trim is commanded OFF, and the transmission shifts into Third gear.

Pressure Control (PC) Solenoid 4 Trim

The PC solenoid 4 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #36 to the 1-3 clutch regulator valve.

1-3 Clutch Regulator Valve

PCS 4 signal fluid, at the 1-3 clutch regulator valve, opposes 1-3 clutch regulator valve spring force and 13 clutch feedback fluid pressure to regulate line or auxiliary line pressure into the 13 clutch/A cooling feed circuit.

#2 Encapsulated Ball Check Valve

13 clutch feedback fluid unseats the #2 ball check valve, allowing excess pressure to pass into the actuator feed limit circuit. This helps to control clutch apply fluid pressure and clutch apply feel.

Shift Solenoid Valve - Mode A

Solenoid 1 signal fluid is routed to the shift solenoid valve - mode A and moves the valve against shift solenoid valve - mode A spring force to the applied position. This allows 13 clutch/A cooling feed fluid to enter the 13 clutch circuit.

1-3 Clutch Assembly

13 clutch fluid enters the transmission case assembly and moves the 1-3 clutch piston against spring force to apply the 1-3 clutch plates.

#4 Pressure Switch

Solenoid 1 signal fluid passes through the 1-3 clutch regulator valve into the PS4 fluid passage. PS4 fluid opens the normally closed #4 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.

Pressure Control (PC) Solenoid 3 Trim

The PC solenoid 3 trim is de-energized (OFF) allowing PCS 3 signal fluid to exhaust from the hybrid low, 1-2 clutch regulator valve; the hybrid low, 1-2 clutch boost valve; and the shift solenoid valve - mode B.

Shift Solenoid 2

The shift solenoid 2 is energized, allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #40 to the shift solenoid valve - mode B.

Hybrid Low, 1-2 Clutch Assembly

HL 12 clutch fluid exhausts from the hybrid low, 1-2 clutch to the shift solenoid valve - mode B allowing the hybrid low, 1-2 clutch to release.

Shift Solenoid Valve - Mode B

Solenoid 2 signal fluid is routed to the shift solenoid valve - mode B and moves the valve against shift solenoid valve - mode B spring force to the applied position. This allows HL 12 clutch fluid pressure to exhaust through the valve into the backfill circuit. Also, HD 234 clutch/B cooling feed fluid replaces HD 234 clutch supply fluid, in order to feed the HD 234 clutch circuit and keep the hybrid direct, 2-3-4 clutch applied.

Hybrid Low, 1-2 Clutch Boost Valve

Hybrid low, 1-2 clutch boost valve spring force moves the hybrid low, 1-2 clutch boost valve to the released position, allowing HL 12 clutch/4th clutch feedback fluid pressure to exhaust into the HL 12 clutch/4th clutch feed circuit.

Hybrid Low, 1-2 Clutch Regulator Valve

Hybrid low, 1-2 clutch regulator valve spring force moves the hybrid low, 1-2 clutch regulator valve to the released position, allowing HL 12 clutch/4th clutch feed fluid pressure to exhaust through the valve in the backfill circuit.

Clutch Piston Exhaust Blowoff Ball Valve

Excess fluid pressure in the backfill circuit exhausts at the clutch piston exhaust blowoff ball valve in order to maintain a constant backfill fluid pressure of 2 psi.

#5 Pressure Switch

The applied shift solenoid valve - mode B closes off the PS5 circuit exhaust, allowing fluid pressure in the circuit to build to actuator feed limit fluid pressure. PS5 fluid opens the normally closed #5 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.

#1 Pressure Switch

Actuator feed limit fluid passes through the hybrid low, 1-2 clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.

#3 Pressure Switch

Actuator feed limit fluid passes through the hybrid low, 1-2 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signaling the TCM that the transmission is in Drive Range - Third Gear.