Hummer H3. Manual — part 872

Fig. 491: Overdrive Range, Third Gear Hydraulic Circuit Diagram
Courtesy of GENERAL MOTORS CORP.

OVERDRIVE RANGE, FOURTH GEAR - TORQUE CONVERTER CLUTCH APPLIED

At higher vehicle speeds, the Hydra-matic 4L60-E transmission uses an overdrive gear ratio
(fourth gear) in order to increase fuel economy and in order to maximize engine performance.
When vehicle operating conditions are appropriate, the PCM energizes the 1-2 shift solenoid
valve to shift the transmission into fourth gear.

1-2 Shift Solenoid (SS) Valve

Energized (turned ON) by the PCM, the normally open solenoid closes and blocks signal A fluid
from exhausting through the solenoid. This creates pressure in the signal A fluid circuit.

2-3 Shift Solenoid (SS) Valve

De-energized (OFF) as in third gear, the 2-3 shift solenoid valve exhausts signal B fluid through
the solenoid.

1-2 Shift Valve

D432 fluid pressure from the 2-3 shift valve and spring force hold the valve in the upshift position

2007 Hummer H3

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

against signal A fluid pressure.

3-4 Shift Valve

Signal A fluid pressure moves the valve into the upshift position against the spring force. In this
position, the valve routes 3-4 signal fluid into the 4th signal fluid circuit.

3-4 Relay Valve and 4-3 Sequence Valve

4th signal fluid pressure moves both valves into the upshift (fourth gear) position against the
spring force acting on the 4-3 sequence valve. This causes the following changes:

Orificed (#7) 2nd fluid is routed through the 3-4 relay valve and into the servo feed fluid
circuit.

Servo feed fluid is routed through the 4-3 sequence valve and into the 4th fluid circuit.

3-4 accumulator fluid routed from the 2-3 shuttle valve is blocked by both valves.

2-4 Servo Assembly

4th fluid is routed through the center of the servo apply pin and acts on the apply side of the 4th
apply piston. 4th fluid pressure moves the 4th apply piston against the apply pin spring force
acting on the release side of the 4th apply piston. This action moves the apply pin and applies the
2-4 band in order to obtain fourth gear.

2-4 Band Apply Accumulation

2-3 Shift Valve Train

The valve train remains in the upshift position with the AFL fluid pressure acting on the 2-3 shift
valve. In addition to its operation third gear, the 2-3 shift valve directs servo feed fluid into the 3-
4 accumulator fluid circuit.

3-4 Accumulator Assembly

3-4 accumulator fluid pressure moves the 3-4 accumulator piston against spring force and orificed
accumulator fluid pressure. This action absorbs initial 4th clutch apply fluid pressure in order to
cushion the 2-4 band apply. Remember that both of the 3-4 accumulator and 4th fluid circuits are
fed by servo feed fluid. As 3-4 accumulator fluid fills the accumulator, any air in the system will
exhaust through office #19. This piston movement forces some orificed accumulator fluid out of
the 3-4 accumulator assembly.

3-4 Accumulator Checkball (#1)

2007 Hummer H3

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

The accumulator fluid forced from the accumulator unseats the #1 checkball and enters the
accumulator fluid circuit. This fluid is routed to the accumulator valve. This is shown by the
arrow directions in the fluid circuit.

Accumulator Valve

Accumulator fluid forced from the 3-4 accumulator is orificed to the end of the accumulator
valve. This fluid pressure, in addition to spring force and torque signal fluid pressure, regulates
the exhaust of excess accumulator fluid pressure through the middle of the valve. This regulation
helps control the 2-4 band apply feel.

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.

Torque Converter Clutch Applies

TCC Solenoid Valve

When operating conditions are appropriate, the PCM energizes the normally open TCC solenoid
valve. This closes the solenoid, blocks the converter feed fluid from exhausting and creates
pressure in the converter feed fluid circuit at the converter clutch apply valve and TCC solenoid
valve.

Converter Clutch Apply Valve

Converter feed fluid pressure moves the valve against spring force and into the apply position. In
this position, release fluid is open to an exhaust port and regulated apply fluid fills the apply fluid
circuit. Converter feed fluid is routed through the converter clutch apply valve to feed the cooler
fluid circuit.

Torque Converter

Release fluid from behind the pressure plate exhausts through the end of the turbine shaft. Apply
fluid pressure is routed between the converter hub and stator shaft where it enters the torque
converter. This fluid applies the converter clutch against the converter cover and keeps the
converter filled with fluid.

TCC Apply Checkball (#9)

Release fluid, exhausting from the converter, seats the #9 checkball located in the end of the

2007 Hummer H3

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

turbine shaft and is orificed around the ball. Orificing the exhausting release fluid controls the
converter clutch apply rate, along with the TCC PWM solenoid valve.

TCC PWM Solenoid Valve

The torque converter clutch pulse width modulation (TCC PWM) solenoid valve controls the
regulated apply valve position. This is done through the use of pulse width modulation (duty
cycle operation). The solenoid duty cycle is controlled by the PCM in relation to vehicle
operating conditions and regulates actuator feed limit (AFL) fluid into the CC signal circuit,
through the #9 orifice and to the isolator valve. This controls line pressure flow through the
regulated apply valve, into the regulated apply circuit and provides a smooth engagement of the
TCC.

Fig. 492: Overdrive Range, Fourth Gear - TCC Applied Hydraulic Circuit Diagram
Courtesy of GENERAL MOTORS CORP.

OVERDRIVE RANGE, 4-3 DOWNSHIFT

When the transmission is operating in fourth gear, a forced 4-3 downshift occurs if there is a
significant increase in throttle position. At minimum throttle, the vehicle speed decreases
gradually (coastdown) and the PCM commands a 4-3 downshift. The PCM also initiates a forced
4-3 downshift when the throttle position remains constant but engine load is increased, such as

2007 Hummer H3

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