Hummer H2. Manual - part 2592

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 

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 (All Except Y-Car) 

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. 

 

2004 Hummer H2 

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

  

Fig. 326: Overdrive Range, First Gear 
Courtesy of GENERAL MOTORS CORP.

 

2004 Hummer H2 

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

  

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 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. 

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.

 

2004 Hummer H2 

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

  

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 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). 

Overrun Clutch Applied - M33 Only 

In order to achieve the highest fuel efficiency, the overrun clutch is applied during vehicle coast and braking. 
With the transmission in overdrive and either second or third gear, the overrun clutch is applied, allowing power 
to be transferred back through the torque converter to the electric machine and engine. 

With the transmission in the D4 range and in either third or second gear, the M33 model applies the overrun 
clutch in order to maximize fuel efficiency during vehicle coast and braking. In this state, vehicle inertia is used 
to drive the engine and the electrical machine through the transmission. While in D4 third gear, the 2-3 SS valve 
is de-energized and the 2-3 shift valve train is in the upshift position. However, D3 oil is not available to apply 
the overrun clutch. In order to apply the overrun clutch, the spacer plate is used to redirect D2 oil to the overrun 
clutch circuit through the 2-3 valve train. 

 

2004 Hummer H2 

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