Overdrive Range First Gear

Overdrive Range - First Gear:

OVERDRIVE RANGE 1ST. GEAR

When the gear selector lever is moved to the Overdrive position, the manual valve is repositioned to allow line pressure to flow in it's respective circuits.

- Manual Valve: In the Overdrive range first gear, line pressure from the pressure regulator valve is directed as PRND4, PR(ND43 and Drive fluid pressures. The PRND4 fluid pressure is directed to the Pressure Switch Manifold (PSM) and to the 2-3 shift valve, the PRND43 fluid is directed to the PSM and to the front servo, and the Drive fluid is directed to the PSM, forward clutch, 1-2 shift valve and accumulator valve.
- Pressure Switch Manifold (PSM): Drive, PRND4 and PRND43 fluid pressures from the manual valve are directed to the DR, PRND4 and PRND43 switches on the PSM, this sends a signal to the Powertrain Control Module (PCM) that the transmission is in Overdrive range.
- Solenoid "A": Energized, signal "A" fluid pressure forces the 1-2 shift valve to the extreme left against spring force.
- Solenoid "B": De-energized, exhausting signal "B" fluid through the solenoid. Spring force holds the 2-3 shift valve to the extreme right.
- 1-2 Shift Valve: Drive fluid pressure from the manual valve is held at the 1-2 shift valve to be utilized in other gear ranges.
- 2-3 Shift Valve: PRND4 fluid pressure from the manual valve is held at the 2-3 shift valve to be utilized in other gear ranges.
- A shift valve: Held to the extreme left by signal "A" pressure. PRN fluid pressure is blocked by the manual valve.
- Forward Clutch: Drive fluid pressure from the manual valve is directed through the case, pump housing and the turbine shaft into the forward clutch housing which applies the forward clutch, this shifts the transmission into first gear.