GM Service Manual Online
For 1990-2009 cars only

Manual Third Gear L4 Hybrid

Important: The operating states for the shift solenoids follow the normal operation depending on vehicle driving conditions.

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch is applied in all manual ranges in order to provide engine compressing braking whenever appropriated.

Under certain conditions the hybrid vehicles engine will shut off and the electric auxiliary transmission fluid pump will start running to keep the transmission pressurized and ready for the engine restart. This engine off condition is a fuel economy feature and the L4 hybrid transmission's electric auxiliary fluid pump is an enabling component.

Fourth Gear Hydraulically Prevented

Manual Valve

The manual valve moves into the Manual Third (3) position and line pressure enters the D321 fluid circuit. Also the manual valve blocks line pressure from the PRND4 fluid circuit and the PRND4 fluid exhausts past the manual valve.

3-4 Shift Valve

D321 fluid pressure assists a spring force in order to keep the valve in the Third gear position under any conditions. this opens the Forth band fluid circuit to an orificed exhaust and the Intermediate and Fourth band releases, thereby preventing Fourth gear.

A/T Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly

PRND4 fluid exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual Third position.

Manual Third -- Second and First Gears

The transmission operates the same in Manual Third as in Overdrive range with the exception that Fourth gear is prevented. The transmission will upshift and downshift between First, Second, and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First and Second gears, and the vehicle will coast when you release the throttle.

Manual Range 3rd - L4 Hybrid


Object Number: 1814435  Size: FS

Manual Third Gear With Electronic Range Select Mode

Important: The operating states for the shift solenoids follow the normal operation depending on vehicle driving conditions

A manual 4-3 downshift is accomplished by moving the gear selector lever to the Manual Third (3) position. In Manual Third the transmission is hydraulically prevented from upshifting into Fourth gear under any conditions. Also, the coast clutch is applied in all manual ranges in order to provide engine compressing braking whenever appropriated.

Fourth Gear Hydraulically Prevented

Manual Valve

The manual valve moves into the Manual Third (3) position and line pressure enters the D321 fluid circuit. Also the manual valve blocks line pressure from the PRND4 fluid circuit and the PRND4 fluid exhausts past the manual valve.

3-4 Shift Valve

D321 fluid pressure assists a spring force in order to keep the valve in the Third gear position under any conditions. this opens the Forth band fluid circuit to an orificed exhaust and the Intermediate and Fourth band releases, thereby preventing Fourth gear.

A/T Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly

PRND4 fluid exhausts from the TFP Val. Position Sw. Assembly, which signals to the PCM that the manual valve is in the Manual Third position.

Manual Third -- Second and First Gears

The transmission operates the same in Manual Third as in Overdrive range with the exception that Fourth gear is prevented. The transmission will upshift and downshift between First, Second, and Third gears as in Overdrive range. However, engine compression braking is not available in Manual Third - First and Second gears, and the vehicle will coast when you release the throttle.

Manual Range 3rd - With Electronic Range Select Mode


Object Number: 1205864  Size: FS