Hummer H3. Manual — part 871

in preparation for a 3-4 upshift.

3-2 Downshift Valve

Spring force holds the valve closed, blocking the 2nd fluid and the 2nd clutch fluid. This valve is
used in order to help control the 3-2 downshift.

3-2 Control Solenoid Valve

In second gear, the PCM energizes the normally closed solenoid. This opens the AFL fluid circuit
to fill the 3-2 signal fluid circuit.

3-2 Control Valve

The 3-2 signal fluid pressure moves the valve against the spring force. This action does not affect
the transmission operation in second gear.

3-4 Shift Valve

Signal A fluid pressure exhausts and spring force moves the valve into the downshift position
(second and third gear positions).

Torque Converter Clutch

TCC Solenoid Valve

Under normal operating conditions, in Overdrive Range-Second Gear, the PCM keeps the
normally open TCC solenoid valve de-energized. Converter feed fluid exhausts through the open
solenoid and spring force keeps the converter clutch apply valve in the release position.

2007 Hummer H3

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3

Fig. 490: Overdrive Range, Second Gear Hydraulic Circuit Diagram
Courtesy of GENERAL MOTORS CORP.

OVERDRIVE RANGE, THIRD GEAR

As vehicle speed increases further and other vehicle operating conditions are appropriate, the
PCM de-energizes the normally open 2-3 shift solenoid valve in order to shift the transmission
into Third gear.

2-3 Shift Solenoid (SS) Valve

De-energized (turned OFF) by the PCM, the solenoid opens and actuator feed limit signal B fluid
exhausts through the solenoid.

Note: AFL fluid continues to feed signal B fluid to the solenoid through orifice #29. However,
the exhaust port through the solenoid is larger than orifice #29 to prevent a buildup of pressure in
the signal B fluid circuit at the solenoid end of the 2-3 shift valve. Exhausting signal B fluid is
represented by the arrows through the solenoid.

2-3 Shift Valve Train

AFL fluid pressure at the 2-3 shift valve moves the valve train toward the solenoid. In the

2007 Hummer H3

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3

upshifted position, the following changes occur:

AFL fluid is routed through the 2-3 shift valve and fills the D432 fluid circuit.

2nd fluid is blocked from entering the servo feed fluid circuit and is orificed (#28) into the
3-4 signal fluid circuit. This orifice helps control the 3-4 clutch apply rate.

Servo feed fluid exhausts past the valve into the 3-4 accumulator fluid circuit and through an
exhaust port at the 3-4 relay valve.

3-4 Clutch Exhaust Checkball (#4)

3-4 signal fluid unseats the ball and enters the 3-4 clutch fluid circuit.

3-4 Clutch Piston

3-4 clutch fluid pressure moves the piston to apply the 3-4 clutch plates and obtain 3rd gear.
However, the 2-4 band must release as the 3-4 clutch applies.

3rd Accumulator Checkball (#2)

3-4 clutch fluid pressure unseats the ball and fills the 3rd accumulator fluid circuit.

3rd Accumulator Exhaust Checkball (#7)

3rd accumulator fluid seats the ball against the orificed exhaust and is routed to the released side
of the 2nd apply piston. Before the #7 checkball seats, air in the 3rd accumulator fluid circuit is
exhausted through the orifice.

2-4 Servo Assembly

3rd accumulator fluid pressure acts on the release side of the 2nd apply piston and assists servo
return spring force. The surface area on the release side of the piston is greater than the surface
area on the apply side. Therefore, 3rd accumulator fluid pressure and servo return spring force
move the 2nd apply piston against 2nd clutch fluid pressure. This action serves two functions:

Move the apply pin to release the 2-4 band.

Act as an accumulator by absorbing initial 3-4 clutch fluid to cushion the 3-4 clutch apply
rate. Remember that the 3rd accumulator fluid circuit is fed by 3-4 clutch fluid.

3-2 Downshift Valve

3-4 clutch fluid pressure moves the valve against spring force. This opens the valve and allows
2nd fluid to feed the 2nd clutch fluid circuit through the valve.

2007 Hummer H3

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3

3-2 Control Solenoid Valve and 3-2 Control Valve

The solenoid remains open and routes AFL fluid into the 3-2 signal fluid circuit. 3-2 signal fluid
pressure holds the 3-2 control valve against spring force, thereby blocking the 3rd accumulator
and 3-4 clutch fluid circuits.

1-2 Shift Solenoid (SS) Valve and 1-2 Shift Valve

The 1-2 SS valve remains de-energized and signal A fluid is exhausted through the solenoid. Also,
D432 fluid pressure from the 2-3 shift valve assists spring force to hold the 1-2 shift valve in the
upshifted position.

3-4 Shift Valve

Spring force holds the valve in the downshifted position, blocking 3-4 clutch fluid in preparation
for a 3-4 upshift.

Torque Converter Clutch

TCC Solenoid Valve

Under normal operating conditions, in Overdrive Range-Third Gear, the PCM keeps the normally
open TCC solenoid valve de-energized. Converter feed fluid exhausts through the open solenoid
and spring force keeps the converter clutch apply valve in the release position. However, at
speeds above approximately 121 km/h (75 mph), with the transmission still in third gear, the
PCM will command TCC apply in third gear. Refer to Overdrive Range, Fourth Gear -
Torque Converter Clutch Applied for more information on TCC apply.

2007 Hummer H3

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3