Overdrive Range - First Gear

Overdrive Range - First Gear:

OVERDRIVE RANGE - FIRST GEAR

When the gear selector lever is moved to Overdrive Range D, the manual valve moves and allows line pressure to fill the drive fluid circuit. Changes to the hydraulic and electrical systems in the transaxle are as follows:

FORWARD CLUTCH APPLIES:

Manual Valve: Mechanically controlled through the gear selector lever, it directs line pressure into the PRND43, PRND4 and drive circuits. Drive fluid pressure is then routed to check- ball #5, the forward orifice bypass valve, the 1-2 shift valve, the 2-3 shift valve, and through orifice #19.

Pressure Switch: Line fluid pressure closes the D4, PRND4 and PRND43 pressure switches, thereby completing their circuits. The sequence of open and closed switches provides input to the PCM indicating the manual valve position.

Solenoid "A": Energized (ON) by the PCM, high pressure in the solenoid "A" fluid circuit holds the 1-2 shift valve in the downshifted position and the 3-4 shift valve in the upshifted position.

1-2 Shift Valve: Held in the downshifted position, it allows orificed lo feed fluid to pass through the valve and enter the lo/reverse band reduce passage. Lo/reverse band reduce fluid is then routed to checkball #6 and also to the spring side of the lo/reverse servo piston.

Solenoid "B": De-energized (OFF) by the PCM, it allows high solenoid "B" pressure to exhaust through the solenoid while maintaining low pressure in the circuit at the 1-2 shift valve.

#5 Checkball (Drive/Forward Clutch): Located in the valve body, drive fluid seats the checkball against the spacer plate thereby routing drive fluid through orifice #1 into the forward clutch circuit. Forward clutch fluid is then routed to checkball #1 and the forward clutch piston to apply the forward clutch.

#1 Checkball (Forward Clutch): Located in the accumulat0r housing, it is unseated by forward clutch pressure allowing forward clutch fluid to actuate the forward accumulator piston.

Forward Orifice (Bypass) Valve: Held closed by spring force, it opens under high pressure and routes drive fluid into the forward clutch circuit. The function of this valve is to provide an additional feed into the forward clutch circuit in order to quickly apply and hold the forward clutch.

Forward Accumulator: Forward clutch fluid actuates the forward accumulator piston during the apply of the forward clutch. Primary accumulator fluid on the spring side of the piston is forced back through its circuit to the 1-2 & 3-4 accumulator valve.

1-2 & 3-4 Accumulator Valve: Biased by torque signal and orificed primary accumulator fluid pressures, it regulates the exhaust of primary accumulator fluid during the apply of the forward clutch.

2-3 Shift Valve: Held in the downshifted position by spring force, it allows lo feed fluid to pass through the valve and enter the lo fluid passage. Lo fluid is then routed to checkball #8 where it seats the checkball to prevent fluid from exhausting at the manual valve.



LO/REVERSE BAND APPLIED

Lo/Reverse Servo: Lo & reverse band reduce fluid from the 1-2 shift valve seats checkball #6 against the lo & reverse band apply passage. Fluid is then routed to the spring side of the lo/reverse servo piston and, into the reverse clutch circuit. In this gear range, the lo/reverse band remains applied despite spring force and lo & reverse band pressure acting on the lo/reverse servo piston.

#6 Checkball (Lo & Reverse Band Apply/Reduce): Held against the lo & reverse band apply circuit, it routes fluid to the reverse clutch circuit. Reverse clutch fluid is then routed to the manual valve where it exhausts.

1-2 Shift Valve: Operating in the downshifted position, lo/reverse band apply fluid passes through the valve and enters the orificed PRN circuit. Orificed PRN fluid is then routed to the manual valve where it exhausts.