Fourth Gear

Drive Range - Fourth Gear

As vehicle speed increases, the TCM processes input signals from the output speed sensor, the TP sensor and other vehicle sensors to determine the precise moment to command ON the normally high pressure control solenoid 3 trim to regulate 4th clutch apply. At the same time, the normally low pressure control solenoid 4 trim is commanded OFF and the transmission shifts into Fourth gear.

4th Clutch Applies

Pressure Control (PC) Solenoid 3 Trim

The PC solenoid 3 trim is energized (ON) allowing actuator feed limit fluid to enter the PCS 3 signal circuit. PCS 3 signal fluid is then routed through orifice 30 to the variable low and 1-2 reverse and 4th clutch regulator valve; through orifice 12 to the variable low and 1-2 reverse and 4th clutch boost valve; and to the shift solenoid valve - mode B.

Variable Low and 1-2 Reverse and 4th Clutch Regulator Valve

PCS 3 signal fluid, at the variable low and 1-2 reverse and 4th clutch regulator valve, opposes variable low and 1-2 reverse and 4th clutch regulator valve spring force and VL 12 reverse/4th clutch feedback fluid pressure to regulate line or auxiliary line pressure into the VL 12 reverse/4th clutch feed circuit.

Variable Low and 1-2 Reverse and 4th Clutch Boost Valve

PCS 3 signal fluid pressure acts on a differential area of the variable low and 1-2 reverse and 4th clutch boost valve, moving the valve against variable low and 1-2 reverse and 4th clutch boost valve spring force to regulate VL 12 reverse/4th clutch feed fluid into the VL 12 reverse/4th clutch feedback circuit. As PCS 3 signal fluid pressure is increased to a given value, the variable low and 1-2 reverse and 4th clutch boost valve opens the VL 1-2 reverse/4th clutch feedback circuit to exhaust. This results in the variable low and 1-2 reverse and 4th clutch regulator valve moving to the full feed position, sending full VL 12 reverse/4th clutch feed pressure (full line pressure) to the 4th clutch.

Shift Solenoid Valve - Mode B

VL 12 reverse/4th clutch feed fluid is routed to the shift solenoid valve - mode B, where it passes through the valve into the 4th clutch/B cooling feed circuit.

Shift Solenoid Valve - Mode A

4th clutch/B cooling feed fluid is routed to the shift solenoid valve - mode A, where it passes through the valve into the 4th clutch circuit.

4th Clutch Assembly

4th clutch fluid pressure enters the case cover assembly behind the 4th clutch piston and moves the piston against spring force to apply the 4th clutch plates.

1-3 Reverse Clutch Releases

Pressure Control (PC) Solenoid 4 Trim

The PC solenoid 4 trim is commanded OFF, allowing PCS 4 signal fluid to exhaust from the 1-3 reverse clutch regulator valve.

1-3 Reverse Clutch Assembly

13 reverse clutch fluid pressure is exhausted from the transmission fluid pump cover, allowing 1-3 reverse clutch spring force to move the 1-3 reverse clutch piston and release the 1-3 reverse clutch plates.

Shift Solenoid Valve - Mode A

Exhausting 13 reverse clutch fluid pressure passes through the shift solenoid valve - mode A into the 13 reverse clutch/A cooling feed circuit.

#3 Ball Check Valve

13 reverse clutch feedback fluid pressure exhausts into the 13 reverse clutch/A cooling feed circuit, allowing actuator feed limit fluid to seat the ball.

1-3 Reverse Clutch Regulator Valve

1-3 reverse clutch regulator valve spring force moves the 1-3 reverse clutch regulator valve to the released position, allowing 13 reverse clutch/A cooling feed fluid pressure to exhaust.

Shift Accumulation

4th Clutch Accumulator

4th clutch fluid is also sent to the 4th clutch accumulator assembly. 4th clutch fluid moves the 4th clutch accumulator piston against accumulator spring force to cushion the apply of the 4th clutch assembly.

1-3 Reverse Clutch Accumulator

13 reverse clutch fluid also exhausts from the 1-3 reverse clutch accumulator assembly. Accumulator spring force moves the 1-3 reverse clutch accumulator piston to the released position.

Drive Range, Fourth Gear