Overdrive Range - Second Gear

Overdrive Range - Second Gear:

Description:

OVERDRIVE RANGE - SECOND GEAR

As vehicle speed increases, and other operating conditions are appropriate, the PCM de-energizes the 1-2 shift solenoid to shift the transmission into Second gear.

1-2 Shift Solenoid: De-energized (turned OFF) by the PCM, the normally open solenoid opens and signal "A" fluid exhausts through the solenoid.

Note: Actuator Fluid limit (AFL) fluid continues to feed the signal "A fluid circuit through orifice #25. However the exhaust port through the solenoid is larger than orifice #25 to prevent a pressure buildup in the signal "A" fluid circuit. Exhausting signal "A" fluid is represented by the blue arrows.

2-3 Shift Solenoid: Energized (ON) as in First gear, it blocks AFL fluid from exhausting through the solenoid. This maintains AFL fluid pressure at the solenoid end of the 2-3 shift valve.

2-4 BAND APPLIES

1-2 Shift Valve: Without signal "A" fluid pressure, spring force moves the valve into the upshifted position. D4 fluid is routed through the valve and fills the 2nd fluid circuit.

1-2 Shift Checkball (#8): 2nd fluid pressure seats the #8 checkball, flows through orifice #16 and fills the 2nd clutch fluid circuit. This orifice helps control the 2-4 band apply rate.

2-4 Servo Assembly: 2nd clutch fluid pressure moves the 2nd apply piston against servo cushion and servo return spring forces. The apply piston moves the band apply pin to apply the 2-4 band. These spring forces help control the 2-4 band apply rate.

1-2 Accumulator: 2nd clutch fluid pressure also moves the 1-2 accumulator piston against spring force and accumulator fluid pressure. This action absorbs initial 2nd clutch fluid pressure to cushion the 2-4 band apply rate. Also, the movement of the 1-2 accumulator piston forces some accumulator fluid out of the accumulator assembly. This accumulator fluid is routed back to the accumulator valve.

Accumulator Valve: Accumulator fluid forced out of the 1-2 accumulator is orificed (#30) to the end of the accumulator valve. This pressure moves the valve against spring force and torque signal fluid pressure to regulate the exhaust of excess accumulator fluid. This regulation provides additional control for the 2-4 band apply rate. The oil circuit shows the exhaust of accumulator fluid during the shift by the arrow directions in the accumulator fluid circuit.

2-3 Shift Valve Train: AFL fluid pressure from the 2-3 shift solenoid holds the valve train in the downshifted position. 2nd fluid is routed through the 2-3 shuttle valve and fills the servo feed fluid circuit.

3-4 Relay Valve and 4-3 Sequence Valve: Spring force holds these valves in the downshifted position (First, Second and Third gear position). 2nd fluid is blocked by the 3-4 relay valve and servo feed fluid is blocked by both valves in preparation for a 3-4 upshift.

3-2 Downshift Valve: Spring force holds the valve closed, blocking 2nd fluid and 2nd clutch fluid. This valve is used to help control the 3-2 downshift.

3-2 Control Solenoid: In Second gear, the PCM operates the normally closed solenoid at approximately a 90% duty cycle. This opens the AFL fluid circuit to fill the 3-2 signal fluid circuit (at 100% duty cycle the AFL fluid circuit is completely open).

3-2 Control Valve: 3-2 signal fluid pressure moves the valve against spring force. This action does not affect the transmission operation in Second gear.

3-4 Shift Valve: Signal "A" fluid pressure exhausts and spring force moves the valve into the downshift position (Second and Third gear position).

[1][2]TORQUE CONVERTER CLUTCH

Converter Clutch Signal Valve: 2nd clutch fluid pressure opens the valve and line pressure feeds the converter clutch (CC) signal fluid circuit. Converter Clutch (CC) signal fluid is orificed (#8) to the end of the CC signal valve and opposes 2nd clutch fluid pressure. CC signal fluid is routed through a filter and orificed (#4) to the [1][2]Torque Converter Clutch (TCC) solenoid.

TCC Solenoid: Under normal operating conditions in Second gear the PCM keeps the normally open TCC solenoid de-energized (OFF). CC signal fluid exhausts through the open solenoid and spring force keeps the converter clutch apply valve in the release position.

Note: The orifice cup plug (#4) in the CC signal fluid circuit is smaller than the exhaust through the TCC solenoid. Therefore, fluid pressure does not build up at the end of the converter clutch apply valve.