Overdrive Range - Fourth Gear

OVERDRIVE RANGE - 4TH GEAR





When operating conditions are appropriate, the PCM energizes 1-2 shift solenoid to shift the transaxle into fourth gear. In addition, the TCC is applied in fourth gear. The manual valve remains in the overdrive position and line pressure continues to feed the Drive and PRND4 fluid circuits.


Intermediate and 4th Band Applied
1-2 Shift Solenoid: The normally open shift solenoid is energized by the PCM and blocks 1-2 signal fluid from exhausting. 1-2 signal fluid pressure is routed to both the 1-2 and 3-4 shift valves.
1-2 Shift Valve: 1-2 signal fluid pressure does not affect the 1-2 shift valve. Spring force and 2-3 signal fluid pressure keep the 1-2 shift valve in the upshifted position.
3-4 Shift Valve: 1-2 signal fluid pressure moves the valve against spring force and into the fourth gear position. 3-4 drive fluid is routed into the 4th band fluid circuit.
Intermediate and 4th Servo: 4th band fluid pressure acts on the outer area of the servo piston to move the servo pin and apply the intermediate/4th band.


Shift Accumulation
3-4 Accumulator: 4th band fluid is also routed to the 3-4 accumulator piston. 4th band fluid pressure moves the piston against spring force and 3-4 accumulator feed fluid pressure. This action absorbs initial 4th band fluid pressure to cushion the intermediate/4th band apply. The movement of the 3-4 accumulator piston forces some accumulator fluid out of the accumulator.
3-4 Accumulator Valve: 3-4 accumulator feed fluid forced from the 3-4 accumulator unseats the #7 checkball and is routed back to the 3-4 accumulator valve. This pressure forces the 1-2/3-4 accumulator valve against spring force and torque signal fluid pressure to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the intermediate/4th band apply. The manual third - third gear illustration shows the exhaust of accumulator fluid during the shift by the arrow directions in the accumulator fluid circuit.


Torque Converter Clutch Applied
TCC Control Solenoid: When conditions are appropriate, the PCM energizes the TCC control solenoid to initiate the TCC apply. The solenoid is Pulse Width Modulated (PWM) to provide a smooth TCC apply. When energized, the solenoid modulates filtered 2-3 drive fluid into the TCC signal fluid circuit
TCC Regulated Apply Valve: TCC signal fluid pressure modulates the valve against spring force and TCC regulated apply fluid pressure. This action directs line pressure into the TCC regulated apply fluid circuit in relation to vehicle operating conditions.
TCC Control Valve: Modulated TCC signal fluid pressure moves the valve against spring force in relation to vehicle operating conditions. This action regulates TCC regulated apply fluid into the apply fluid circuit. At the same time, the release fluid circuit is opened to an orificed exhaust. In this position the valve directs TCC feed limit fluid to feed the cooler fluid circuit.
Torque Converter Clutch: Apply fluid is routed to the torque converter at the same time release fluid exhausts from the converter. Apply fluid pressure applies the TCC.
TR Switch: Release fluid also exhausts from the TR Switch and the TR Switch signals the PCM that the TCC is released.