Hummer H3. Manual — part 870

Forward Clutch Accumulator Checkball (#12)

D4 fluid pressure seats the checkball and is orificed (#22) into the forward clutch feed fluid
circuit. This orifice helps control the forward clutch apply rate.

Forward Clutch Accumulator Piston

Forward clutch feed fluid pressure moves the piston against spring force. This action absorbs
some of the initial increase of forward clutch feed fluid pressure to cushion the forward clutch
apply.

Forward Clutch Abuse Valve

D4 fluid pressure acts on the valve opposite of spring force. At engine speeds greater than idle,
D4 fluid pressure increases and moves the valve against spring force (as shown). D4 fluid can
then quickly fill the forward clutch feed fluid circuit, thereby bypassing the control of orifice #22
and providing a faster apply of the forward clutch. Otherwise, with increased throttle opening
and engine torque, the clutch may slip during apply.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly

D4 fluid pressure is routed to the TFP manual valve position switch and closes the normally open
D4 fluid pressure switch. This signals the PCM that the transmission is operating in Overdrive
range.

1-2 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal A fluid
from exhausting through the solenoid. This maintains pressure in the signal A fluid circuit.

2-3 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal B fluid
from exhausting through the solenoid. This maintains signal B fluid pressure at the solenoid end of
the 2-3 shift valve.

2-3 Shift Valve Train

Signal B fluid pressure at the solenoid end of the 2-3 shift valve holds the valve train in the
downshifted position against AFL fluid pressure acting on the 2-3 shift valve. In this position, the
2-3 shuttle valve blocks AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is
open to an exhaust port past the valve.

1-2 Shift Valve

2007 Hummer H3

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

Signal A fluid pressure holds the valve in the downshifted position against spring force. In the
First gear position, the valve blocks D4 fluid from entering the 2nd fluid circuit.

Accumulator Valve

Biased by torque signal fluid pressure, spring force and orificed accumulator fluid pressure at the
end of the valve, the accumulator valve regulates D4 fluid into accumulator fluid pressure.
Accumulator fluid is routed to both the 1-2 and 3-4 accumulator assemblies in preparation for the
1-2 and 3-4 upshifts respectively.

Rear Lube

D4 fluid is routed through an orifice cup plug (#24) in the rear of the transmission case to feed
the rear lube fluid circuit.

Pressure Control (PC) Solenoid Valve

Remember that the PC solenoid valve continually varies torque signal fluid pressure in relation to
throttle position and vehicle operating conditions. This provides a precise control of line pressure.

3-2 Control Solenoid Valve

The PCM keeps the solenoid OFF in First gear and the normally closed solenoid blocks filtered
AFL fluid from entering the 3-2 signal fluid circuit.

Torque Converter Clutch PWM Solenoid Valve

In first gear, at approximately 6 mph, the PCM operates the TCC PWM solenoid valve at
approximately a 90 percent duty cycle. This opens the AFL fluid circuit, to fill the converter
clutch signal fluid circuit through the #9 orifice and flows to the isolator valve. The CC signal
fluid pressure, acting on the isolator valve, will move the regulated apply valve towards the
closed position. Regulated line pressure is now routed into the regulated apply circuit and flows
to the closed converter clutch valve and is blocked from entering the converter clutch apply
circuit. Regulated apply fluid is routed through the #8 orifice to the front of the regulated apply
valve and regulates the line pressure entering the regulated apply circuit, in response to the CC
signal fluid acting on the isolator valve.

2007 Hummer H3

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

Fig. 489: Overdrive Range, First Gear Hydraulic Circuit Diagram
Courtesy of GENERAL MOTORS CORP.

OVERDRIVE RANGE, SECOND GEAR

As vehicle speed increases and other operating conditions are appropriate, the PCM de-energizes
the 1-2 shift solenoid valve in order to shift the transmission to second gear.

1-2 Shift Solenoid (SS) Valve

De-energized (turned OFF) by the PCM, the normally open solenoid opens and signal A fluid
exhausts through the solenoid.

2-3 Shift Solenoid (SS) Valve

Energized (ON) as in first gear, the 2-3 shift solenoid valve blocks signal B fluid from exhausting

IMPORTANT: The actuator feed limit (AFL) fluid continues to feed the signal A

fluid circuit through orifice #25. However, the exhaust port
through the solenoid is larger than orifice #25 in order to prevent
a pressure buildup in the signal A fluid circuit. Exhausting signal
A fluid is represented by the blue arrows.

2007 Hummer H3

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

through the solenoid. This maintains signal B fluid pressure at the solenoid end of the 2-3 shift
valve.

1-2 Shift Valve

Without signal A fluid pressure, spring force moves the valve into the upshift position. D4 fluid is
routed through the valve and fills the 2nd fluid circuit.

1-2 Shift Checkball (#8)

The 2nd fluid pressure seats the #8 checkball, flows through orifice #16 and fills the 2nd clutch
fluid circuit. This orifice helps control the 2-4 band apply rate.

2-4 Servo Assembly

The 2nd clutch fluid pressure moves the #8 checkball, flows through orifice #16 and fills the 2nd
clutch fluid circuit. This orifice helps to control the 2-4 band apply rate.

1-2 Accumulator

The 2nd clutch fluid pressure also moves the 1-2 accumulator piston against the spring force and
the accumulator fluid pressure. This action absorbs the initial 2nd clutch fluid pressure in order to
cushion the 2-4 band apply rate. Also, the movement of the 1-2 accumulator piston forces some
accumulator fluid out of the accumulator assembly. This accumulator fluid is routed back to the
accumulator valve.

Accumulator Valve

The accumulator fluid forced out of the 1-2 accumulator is orificed (#30) to the end of the
accumulator valve. This pressure moves the valve against the spring force and the torque signal
fluid pressure in order to regulate the exhaust of excess accumulator fluid. This regulation
provides additional control for the 2-4 band apply rate. The fluid circuit shows the exhaust of the
accumulator fluid during the shift by the arrow directions in the accumulator fluid circuit.

2-3 Shift Valve Train

The signal B fluid pressure from the 2-3 shift solenoid valve holds the valve train in the downshift
position. The 2nd fluid is routed through the 2-3 shuttle valve and fills the servo feed fluid circuit.

3-4 Relay Valve and 4-3 Sequence Valve

Spring force holds these valves in the downshift position (first, second and third gear positions).
The 2nd fluid is blocked by the 3-4 relay valve and the servo feed fluid is blocked by both valves

2007 Hummer H3

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