Manual First Gear

Use Manual First for maximum engine braking when the car is descending steep grades. Select Manual First at any vehicle speed. However, the transmission will first downshift into Manual Second. The transmission will later downshift to Manual First when the vehicle is at a specified speed according to vehicle application.

Manual Valve: In the Manual First range, line pressure from the pressure regulator valve is turned into Drive, D321, D21, and Lo fluid pressures. The Drive fluid pressure is directed to the forward clutch. The D321 fluid pressure is directed to the overrun clutch. The D21 fluid pressure is directed to the 2-3 shift valve. The Lo fluid pressure is directed to the Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly and to the low & reverse band servo.

Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly: Lo fluid pressure from the manual valve is directed to the Lo pressure switch on the TFP manual valve position switch. This sends a signal to the Powertrain Control Module (PCM) that the transmission is in Manual First. Drive fluid pressure is also supplied to the TFP manual valve position switch.

1-2 Shift Solenoid (1-2 SS) Valve: When the 1-2 SS valve is energized, 1-2 signal fluid pressure forces the 1-2 and the 3-4 shift valves to the extreme left.

2-3 Shift Solenoid (2-3 SS) Valve: When the 2-3 SS valve is de-energized, 2-3 signal fluid pressure exhausts through the solenoid.

1-2 Shift Valve: 1-2 signal fluid pressure holds the 1-2 shift valve to the extreme left. The actuator feed and the drive pressures supplied to the 1-2 shift valve are blocked.

2-3 Shift Valve: Spring pressure and the D21 fluid pressure from the manual valve hold the 2-3 Shift Valve to the extreme right.

3-4 Shift Valve: 1-2 signal pressure forces the 3-4 shift valve to the extreme left.

Low & Reverse Band Servo: Low fluid pressure from the manual valve is directed to the #7 checkball and to the low & reverse band servo, which applies the low & reverse band. Low fluid pressure changes to Rear Band Apply (RBA) fluid pressure at the checkball.

Forward Clutch: The forward clutch is applied by Drive fluid pressure from the manual valve.

Overrun Clutch: The D321 fluid pressure from the manual valve seats the #1 checkball in the case. This causes the fluid to flow through an orifice, where the D321 fluid pressure changes into overrun fluid pressure. The overrun fluid pressure flows through the case and the pump housing, and into the overrun clutch housing, which applies the overrun clutch. The overdrive roller clutch becomes ineffective and provides vehicle engine compression braking.