Hummer H2. Manual - part 2367

MANUAL SECOND GEAR 

A manual 3-2 downshift can be accomplished by moving the gear selector lever into the Manual Second (2) 
position when the transmission is operating in third gear. This causes the transmission to shift immediately into 
second gear regardless of vehicle operating conditions. Also, the transmission is prevented from operating in 
any other gear, first, third or fourth. The following information explains the additional changes during a manual 
3-2 downshift, as compared to a forced 3-2 downshift. Some vehicles in manual second gear will start out in 
first gear, while other vehicles will have a second gear start. Refer to the owners manual for specific 
applications. 

Manual Valve 

The selector lever moves the manual shaft and the manual valve into the manual second (2) position. This 
allows the line pressure to enter the D2 fluid circuit. 

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly 

The D2 fluid is routed to the TFP manual valve position switch where it opens the normally closed D2 fluid 
pressure switch. With the D2 and the D3 pressure switches closed and the D4 pressure switch open, the TFP 
manual valve position switch signals the PCM that the transmission is operating in manual second. 

Third and Fourth Gears Prevented 

2-3 Shift Solenoid (SS) Valve 

The PCM energizes the 2-3 SS valve and the AFL fluid pressure holds the 2-3 shift valve in the downshift 
position. This electronically prevents operation of the third and fourth gears. 

2-3 Shift Valve Train 

The D2 fluid is routed between the 2-3 shuttle and the 2-3 shift valves and causes the following: 

z

Regardless of the operating conditions, the D2 fluid pressure holds the 2-3 shift valve in the downshift 
position against the AFL fluid pressure.  

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The 2nd fluid is blocked from entering the 3-4 signal fluid circuit and the 3-4 signal fluid circuit is open 
to an exhaust port at the valve.  

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The 3-4 clutch cannot apply with the 3-4 signal fluid exhausted. Therefore, third and fourth gears are 
hydraulically prevented.  

z

The 2nd fluid feeds the servo feed fluid circuit, but the 2nd fluid circuit has no function in manual second. 

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The AFL fluid is blocked by the 2-3 shift valve and the D432 fluid circuit is exhausted through the valve. 

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The overrun fluid is exhausted through the 2-3 shuttle valve.  

1-2 Shift Valve 

The 1-2 SS valve is OFF, the signal A fluid exhausts through the solenoid and the spring force holds the valve 
in the upshifted position. 

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E (Introduction) - Hummer H2

  

First Gear Prevented 

The prevention of first gear is controlled electronically by the PCM through the 1-2 SS valve. The PCM keeps 
the 1-2 SS valve de-energized, regardless of the vehicle operating conditions when the TFP manual valve 
position switch signals manual second gear range. This keeps signal A fluid exhausted and the spring force 
holds the 1-2 shift valve in the upshift position. 

Overrun Clutch Remains Applied 

Overrun Clutch Feed Checkball (#5) 

Orificed D2 fluid pressure seats the #5 checkball against the empty overrun clutch fluid circuit. This is done 
simultaneously with the overrun clutch fluid exhausting so that there is a continuous fluid supply to the overrun 
clutch feed fluid circuit. 

Overrun Clutch Piston 

A continuous supply of fluid pressure is routed to the piston in order to keep the overrun clutch plates applied. 

Torque Converter Clutch 

The converter clutch is released prior to downshifting into manual second-second gear. Under normal operating 
conditions, the TCC will not apply in second gear. 

Pressure Control (PC) Solenoid Valve 

The PCM output signal to the PC solenoid valve increases the operating range of torque signal fluid pressure in 
manual second. This provides the increased line pressure for the additional torque requirements during the 
engine compression braking and increased engine loads.

IMPORTANT: Some vehicles in Manual Second Gear, at a stop, will start out in 1st gear, while 

others will have a second gear start. Refer to Vehicle Owners Manual.

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E (Introduction) - Hummer H2

  

Fig. 473: Manual Second Gear 
Courtesy of GENERAL MOTORS CORP.

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E (Introduction) - Hummer H2

  

MANUAL FIRST GEAR 

A manual 2-1 downshift can be accomplished by moving the gear selector lever into the manual first (1) 
position when the transmission is operating in second gear. The downshift to first gear is controlled 
electronically by the PCM. The PCM will not energize the 1-2 shift solenoid valve to initiate the downshift until 
the vehicle speed is below approximately 48 to 56 km/h (30 to 35 mph). Above this speed, the transmission 
operates in a manual first-second gear state. The following text explains the manual 2-1 downshift. 

Manual Valve 

The selector lever moves the manual shaft and the manual valve into the manual first (1) position. This allows 
the line pressure to enter the Lo fluid circuit. 

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly 

Lo fluid is routed to the TFP manual valve position switch where it closes the normally open lo pressure switch. 
The addition of the lo pressure switch being closed signals to the PCM that manual first is selected. 

2-3 Shift Solenoid (SS) Valve 

In both first and second gears, this solenoid is energized and maintains the signal B fluid pressure at the 
solenoid end of the 2-3 shift valve train. 

2-3 Shift Valve Train 

Held in the downshift position by the signal B fluid pressure from the solenoid, the valve train blocks the AFL 
fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to exhaust past the valve. 

1-2 Shift Solenoid (SS) Valve 

Below approximately 48 to 56 km/h (30 to 35 mph) the PCM energizes the normally open solenoid. This blocks 
the signal A fluid pressure from exhausting through the solenoid and creates the pressure in the signal A fluid 
circuit. Above this speed, the PCM keeps the solenoid de-energized and the transmission operates in manual 
first-second gear. 

1-2 Shift Valve 

Signal A fluid pressure moves the valve against the spring force and into the downshift position. In this 
position, Lo fluid from the manual valve is routed into the Lo/1st fluid circuit and D4 fluid is blocked from 
entering the 2nd fluid circuit. The 2nd fluid exhausts through an orifice and an annulus exhaust port past the 
valve. This orifice (#26) helps control the 2-4 band release during a 2-1 downshift. 

2-4 Band Releases 

2-4 Servo Assembly 

The 2nd clutch fluid, which was fed by the 2nd fluid, exhausts from the servo. This allows the spring force from 
the servo cushion and the servo return springs to move the 2nd apply piston and apply the pin to release the 2-4 

 

2004 Hummer H2 

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E (Introduction) - Hummer H2