Manual First - First Gear (From Manual Second - Second Gear)

Manual First - First Gear (From Manual Second - Second Gear):

Description:

MANUAL FIRST - FIRST GEAR (from Manual Second - Second Gear)

A manual 2-1 downshift can be accomplished by moving the gear selector lever into the Manual First (1) position when the transmission is operating in Second gear. The downshift to First gear is controlled electronically by the PCM. The PCM will not energize the 1-2 shift solenoid to initiate the downshift until vehicle speed is below approximately 48 to 56 km/h (30 to 35 mph). Above this speed, the transmission will operate in a Manual First - Second Gear state. The following text explains the manual 2-1 downshift.

Manual Valve: The selector lever moves the manual shaft and manual valve into the Manual First (1) position. This allows line pressure to enter the lo fluid circuit.

Pressure Switch Assembly (PSA): Lo fluid is routed to the PSA where it closes the normally open lo pressure switch. The addition of the lo pressure switch being closed signals the PCM that Manual First is selected.

2-3 Shift Solenoid: In both First and Second gears this solenoid is energized and maintaining actuator feed limit (AFL) fluid pressure at the solenoid end of the 2-3 shift valve train.

2-3 Shift Valve Train: Held in the downshifted position by AFL fluid pressure from the solenoid, the valve train blocks AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to an exhaust past the valve.

1-2 Shift Solenoid: Below approximately 48 to 56 km/h (30 to 35 mph) the PCM energizes the normally open solenoid. This blocks signal "A" fluid pressure from exhausting through the solenoid and creates pressure in the signal "A" fluid circuit. Above this speed, the PCM keeps the solenoid deenergized and the transmission operates in Manual First - Second Gear.

1-2 Shift Valve: Signal "A" fluid pressure moves the valve against spring force and into the downshifted position. In this position, lo fluid from the manual valve is routed into the lo 1st fluid circuit and D4 fluid is blocked from entering the 2nd fluid circuit. 2nd fluid exhausts through an orifice and an annulus exhaust port past the valve. This orifice (#26) helps control the 2-4 band release during a 2-1 downshift.

2-4 BAND RELEASES

2-4 Servo Assembly: 2nd clutch fluid, which was fed by 2nd fluid, exhausts from the servo. This allows spring force from the servo cushion and servo return springs to move the 2nd apply piston and apply pin to release the 2-4 band. These spring forces help control the 2-4 band release.

1-2 Accumulator Assembly: 2nd clutch fluid also exhausts from the 1-2 accumulator assembly. Spring force and accumulator fluid pressure move the accumulator piston to assist 2nd clutch fluid exhaust.

Accumulator Valve: As accumulator fluid is filling the 1-2 accumulator assembly, the accumulator valve regulates D4 fluid into the accumulator fluid circuit. This regulation, biased by torque signal fluid pressure and spring force, helps control the movement of the 1-2 accumulator piston, 2nd clutch fluid exhaust and the 2-4 band release.

1-2 Upshift Checkball (#8): Exhausting 2nd clutch fluid pressure unseats the ball and is routed through the 2nd fluid circuit.

Converter Clutch Signal Valve: 2nd fluid exhausts from the converter clutch signal valve. Refer to Park range on for a description of the [1][2]Torque Converter Clutch (TCC) signal valve operation in First gear.

LO and REVERSE CLUTCH APPLIES

Lo Overrun Valve: Lo 1st fluid is regulated through the lo overrun valve and into the lo/reverse fluid circuit to control the lo/reverse clutch apply.

Lo/Reverse Piston: Lo/reverse fluid pressure acts on the inner area of the piston to move the piston and apply the lo/reverse clutch plates.

OVERRUN CLUTCH APPLIED

The overrun clutch remains applied in Manual First to provide engine compression braking.

Pressure Control Solenoid: Similar to Manual Second, the PCM output signal to the force motor increases the operating range of torque signal fluid pressure. This provides increased line pressure for the additional torque requirements during engine compression braking and increased engine loads.

3-2 Downshift Control Solenoid and 3-2 Control Valve: In First gear the solenoid is OFF, AFL fluid is blocked by the solenoid, 3-2 signal fluid exhausts through the solenoid and spring force opens the 3-2 control valve.