Volt

Reverse Series Mode Engine On

When the transmission is operating in Reverse - Series Mode (R), and the HPCM determines that operating conditions are appropriate, the internal combustion engine (ICE) is started, the auxiliary fluid pump is turned OFF, and the main fluid pump provides hydraulic fluid pressure (refer to Engine Start ). After Engine Start, the following changes would occur to the transmission's hydraulic and electrical systems.

The 1-3 reverse clutch is applied for Engine Start, and remains applied for Reverse - Series Mode (Engine ON).

Pressure Control (PC) Solenoid 4

The PC solenoid 4 is energised (ON) allowing actuator feed limit fluid to enter the PCS 4 signal circuit. PCS 4 signal fluid is then routed through orifice #18 to the 1-3 reverse clutch regulator valve.

Shift Solenoid 2

The shift solenoid 2 is energised (ON) allowing actuator feed limit fluid to enter the solenoid 2 signal fluid circuit. Solenoid 2 signal fluid is routed through orifice #21 to the shift solenoid valve - mode A. Solenoid 2 signal fluid is also routed to the variable hi and 2-3-4 clutch regulator valve, and to the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Regulator Valve

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

#3 Ball Check Valve

13 reverse clutch feedback fluid unseats the #3 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

13 reverse clutch/A cooling feed fluid passes through the shift solenoid valve - mode A and enters the 13 reverse clutch circuit.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid passes through the case and the transmission fluid pump cover into the 1-3 reverse clutch housing and moves the 1-3 reverse clutch piston against spring force to apply the 1-3 reverse clutch plates.

#1 Pressure Switch

Solenoid 2 signal fluid passes through the 1-3 reverse clutch regulator valve into the PS1 fluid passage. PS1 fluid opens the normally closed #1 pressure switch, signalling the TCM that the transmission is in Reverse - Series Mode.

#3 Pressure Switch

Solenoid 2 signal fluid passes through the variable hi and 2-3-4 clutch regulator valve into the PS3 fluid passage. PS3 fluid opens the normally closed #3 pressure switch, signalling the TCM that the transmission is in Reverse - Series Mode.

Pressure Control (PC) Solenoid 5

The PC solenoid 5 is de-energised (OFF) allowing PCS 5 signal fluid to exhaust from the damper bypass clutch valve.

Torque Damper Clutch Assembly

Damper clutch fluid exhausts from the torque damper clutch assembly to the damper bypass clutch valve allowing the torque damper clutch to release.

Damper Bypass Clutch Valve

Damper bypass clutch valve spring force moves the damper bypass clutch valve to the released position, allowing damper clutch fluid pressure to exhaust through the valve into the exhaust backfill circuit.

Transmission Fluid Temperature (TFT) Sensor

Damper clutch fluid pressure in the exhaust backfill circuit exhausts at the TFT sensor.

Variable Low and 1-2 Reverse Clutch Assembly

With the exception of the switch to line fluid pressure from the main fluid pump assembly, no other changes occur to the variable low and 1-2 reverse clutch fluid circuit and the variable low and 1-2 reverse clutch remains applied.

Pressure Control (PC) Solenoid 2

The PC solenoid 2 is commanded OFF, allowing PCS 2 signal fluid to exhaust from the variable hi and 2-3-4 clutch regulator valve and the variable hi and 2-3-4 clutch boost valve.

Variable Hi and 2-3-4 Clutch Assembly

VH 234 clutch fluid pressure is exhausted from the case assembly, allowing variable hi and 2-3-4 clutch spring force to move the variable hi and 2-3-4 clutch piston and release the variable hi and 2-3-4 clutch plates.

Shift Solenoid Valve - Mode B

Exhausting VH 234 clutch fluid pressure passes through the shift solenoid valve - mode B into the 234 clutch feed circuit.

Shift Solenoid Valve - Mode A

Exhausting 234 clutch feed fluid pressure passes through the shift solenoid valve - mode A into the VH 234 clutch/B cooling feed circuit.

Variable Hi and 2-3-4 Clutch Regulator Valve

Variable hi and 2-3-4 clutch regulator valve spring force moves the variable hi and 2-3-4 clutch regulator valve to the released position, allowing VH 234 clutch/B cooling feed fluid pressure to exhaust.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid is also sent to the 1-3 reverse clutch accumulator assembly. 13 reverse clutch fluid moves the 1-3 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the 1-3 reverse clutch assembly.

Variable Low and 1-2 Reverse Clutch Accumulator

VL 12 reverse clutch fluid is also sent to the variable low and 1-2 reverse clutch accumulator assembly. VL 12 reverse clutch fluid moves the variable low and 1-2 reverse clutch accumulator piston against accumulator spring force to cushion the apply of the variable low and 1-2 reverse clutch assembly.

Variable Hi and 2-3-4 Clutch Accumulator

VH 234 clutch fluid also exhausts from the variable hi and 2-3-4 clutch accumulator assembly. Accumulator spring force moves the variable hi and 2-3-4 clutch accumulator piston to the released position.