Hummer H2. Manual - part 2595

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

 

2004 Hummer H2 

2004 TRANSMISSION/TRANSAXLE Automatic Transmission - Overhaul - 4L60-E/4L65-E

  

Fig. 329: Overdrive Range, Fourth Gear - TCC Applied 
Courtesy of GENERAL MOTORS CORP.

 

2004 Hummer H2 

2004 TRANSMISSION/TRANSAXLE Automatic Transmission - Overhaul - 4L60-E/4L65-E

  

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 driving up a steep incline. To achieve a 4-3 downshift, the PCM 
de-energizes the 1-2 shift solenoid valve and the following changes occur to the transmission's electrical and 
hydraulic systems: 

1-2 Shift Solenoid (SS) Valve 

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

1-2 Shift Valve 

As in Fourth gear, D432 fluid pressure and spring force hold the valve in the upshift position. 

2-4 Band Releases 

3-4 Shift Valve 

With the signal A fluid pressure exhausted, the spring force moves the valve into the downshift position. In this 
position, the valve blocks the 3-4 signal fluid and the 4th signal fluid exhausts past the valve. 

3-4 Relay Valve and 4-3 Sequence Valve 

These valves control the timing of the 2-4 band release. With the 4th signal fluid pressure exhausted, the 3-4 
accumulator fluid pressure moves the 3-4 relay valve into the third gear position. This opens the 3-4 
accumulator fluid to an orificed exhaust (#5) past the 3-4 relay valve (shown by red arrows). Because the 
exhaust is orificed, the 3-4 accumulator fluid pressure momentarily holds the 4-3 sequence valve against spring 
force before completely exhausting. 

When the exhausting 3-4 accumulator fluid pressure decreases sufficiently, the spring force moves the 4-3 
sequence valve into the third gear position as shown. This opens both the 3-4 accumulator and the 4th fluid 
circuits to a quick exhaust past the 4-3 sequence valve. In this position the valve blocks the 2nd fluid from 
entering the servo feed fluid circuit. 

2-4 Servo Assembly 

The 4th fluid exhausts from the 4th apply piston in the servo assembly. The apply pin spring moves the 4th 
apply piston and the apply pin in order to release the band from the reverse input drum and shift the 
transmission into third gear. 

3-4 Accumulator Assembly 

The 3-4 accumulator fluid exhausts from the 3-4 accumulator piston. The orificed accumulator fluid pressure 
and the spring force move the piston into a third gear position.

 

2004 Hummer H2 

2004 TRANSMISSION/TRANSAXLE Automatic Transmission - Overhaul - 4L60-E/4L65-E

  

3-4 Accumulator Checkball (#1) 

As the accumulator fluid fills the 3-4 accumulator, it seats the #1 checkball and is forced through orifice #18. 
This orifice controls the rate at which accumulator fluid pressure fills the 3-4 accumulator and the 3-4 
accumulator fluid exhausts from the accumulator assembly. 

Accumulator Valve 

Biased by torque signal fluid pressure and spring force, the accumulator valve regulates the D-4 fluid into the 
accumulator fluid circuit. 

2-3 Shift Solenoid (SS) Valve 

This solenoid remains de-energized as in fourth gear and the signal B fluid exhausts through the solenoid. 

2-3 Shift Valve Train 

The AFL fluid pressure at the 2-3 shift valve holds the valves in the upshift position. This allows the servo feed 
fluid to exhaust through the valve, into the 3-4 accumulator fluid circuit and past the 4-3 sequence valve. 

Torque Converter Clutch Solenoid Valve 

TCC PWM Solenoid Valve 

The PCM de-energizes the TCC solenoid valve, and operates the duty cycle of the TCC PWM solenoid valve to 
release the converter clutch for a smooth disengagement, prior to initiating the 4-3 downshift. 

Pressure Control (PC) Solenoid Valve 

Remember that the PC solenoid valve continually adjusts the torque signal fluid pressure in relation to the 
various PCM input signals (mainly the throttle position).

 

2004 Hummer H2 

2004 TRANSMISSION/TRANSAXLE Automatic Transmission - Overhaul - 4L60-E/4L65-E