GM Service Manual Online
For 1990-2009 cars only

For a view of the oil flow diagrams, refer to the 1996 TURM manual.

In order to obtain second gear, the PCM receives input signals from the Vehicle Speed Sensor (VSS), from the Throttle Position Sensor (TP Sensor), and from other engine sensors. These signals determine when to de-energize solenoid A.

Manual Valve: In the Overdrive range second gear, line pressure from the pressure regulator valve is directed as PRND4, PRND43, and Drive fluid pressures. The PRND4 fluid pressure is directed to the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly and to the 2-3 shift valve. The PRND43 fluid is directed to the TFP Val. Position Sw. Assembly and to the front servo. The Drive fluid is directed to the TFP Val. Position Sw. assembly, and the forward clutch.

Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly: Drive, PRND4, and PRND43 fluid pressures from the manual valve are directed to the DR, PRND4, and the PRND43 switches on the TFP Val. Position Sw. Assembly. This sends a signal to the PCM that the transmission is in Overdrive range.

1-2 Shift Solenoid (1-2 SS) Valve: When the 1-2 SS Valve is de-energized, signal A fluid exhausts through the solenoid. A spring force holds the 1-2 shift valve to the extreme right.

2-3 Shift Solenoid (1-2 SS) Valve: When the 2-3 SS Valve is de-energized, signal B fluid pressure forces the 2-3 shift valve to the extreme right against a spring force.

1-2 Shift Valve: Spring force holds the 1-2 Shift Valve to the extreme right. Drive fluid pressure from the manual valve changes into 2-3 drive fluid pressure at the 1-2 shift valve. This pressure is directed to the 2-3 shift valve, to the TCC PWM Solenoid Valve, and to the intermediate (second) clutch.

2-3 Shift Valve: Spring force holds the 2-3 Shift Valve to the extreme right. The 2-3 drive fluid pressure from the 1-2 shift valve changes into Front Band Apply (FBA) and is directed to the front servo. The PRND4 fluid pressure from the manual valve is held at the 2-3 shift valve in order to be utilized in other gear ranges.

3-4 Shift Range: Spring force holds the 3-4 Shift Valve to the extreme right.

Forward Clutch: Drive fluid pressure from the manual valve applies the forward clutch.

Intermediate (Second) Clutch: Second fluid pressure from the 1-2 shift valve applies the intermediate clutch. The 2-3 drive fluid pressure from the 1-2 shift valve seats the #4 checkball, causing the fluid to flow through two orifices and into the center support. This applies the Intermediate (Second) clutch. The 2-3 drive fluid pressure changes into Second apply fluid pressure at the orifices.