2-3 Shift Solenoid (SS) Valve
In both first and second gears, this solenoid is energized and maintains the signal B fluid pressure
at the solenoid end of the 2-3 shift valve train.
2-3 Shift Valve Train
Held in the downshift position by the signal B fluid pressure from the solenoid, the valve train
blocks the AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to
exhaust past the valve.
1-2 Shift Solenoid (SS) Valve
Below approximately 48 to 56 km/h (30 to 35 mph) the PCM energizes the normally open
solenoid. This blocks the signal A fluid pressure from exhausting through the solenoid and creates
the pressure in the signal A fluid circuit. Above this speed, the PCM keeps the solenoid de-
energized and the transmission operates in manual first-second gear.
1-2 Shift Valve
Signal A fluid pressure moves the valve against the spring force and into the downshift position.
In this position, Lo fluid from the manual valve is routed into the Lo/1st fluid circuit and D4 fluid
is blocked from entering the 2nd fluid circuit. The 2nd fluid exhausts through an orifice and an
annulus exhaust port past the valve. This orifice (#26) helps control the 2-4 band release during a
2-1 downshift.
2-4 Band Releases
2-4 Servo Assembly
The 2nd clutch fluid, which was fed by the 2nd fluid, exhausts from the servo. This allows the
spring force from the servo cushion and the servo return springs to move the 2nd apply piston and
apply the pin to release the 2-4 band. These spring forces help control the 2-4 band release.
1-2 Accumulator Assembly
The 2nd clutch fluid also exhausts from the 1-2 accumulator assembly. The spring force and the
accumulator fluid pressure move the accumulator piston to assist the 2nd clutch fluid exhaust.
Accumulator Valve
As the accumulator fluid is filling the 1-2 accumulator assembly, the accumulator valve regulates
the D4 fluid into the accumulator fluid circuit. This regulation, biased by torque signal fluid
pressure and spring force, helps control the movement of the 1-2 accumulator piston. The 2nd
2007 Hummer H3
2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3