Hummer H2. Manual - part 2368

band. These spring forces help control the 2-4 band release.

1-2 Accumulator Assembly 

The 2nd clutch fluid also exhausts from the 1-2 accumulator assembly. The spring force and the accumulator 
fluid pressure move the accumulator piston to assist the 2nd clutch fluid exhaust. 

Accumulator Valve 

As the accumulator fluid is filling the 1-2 accumulator assembly, the accumulator valve regulates the D4 fluid 
into the accumulator fluid circuit. This regulation, biased by torque signal fluid pressure and spring force, helps 
control the movement of the 1-2 accumulator piston. The 2nd clutch fluid exhaust, and the 2-4 band release. 

1-2 Upshift Checkball (#8) 

Exhausting the 2nd clutch fluid pressure unseats the ball and is routed through the 2nd fluid circuit. 

Lo and Reverse Clutch Applies 

Lo Overrun Valve 

The Lo/1st fluid is regulated through the lo overrun valve and into the Lo/reverse fluid circuit in order to control 
the lo and reverse clutch apply. 

Lo and Reverse Piston 

The Lo/reverse fluid pressure acts on the inner area of the piston in order to move the piston and in order to 
apply the lo and reverse clutch plates. 

Overrun Clutch Applied 

The overrun clutch remains applied in manual first in order to provide engine compression braking. 

Pressure Control (PC) Solenoid Valve 

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

3-2 Downshift Control Solenoid Valve and the 3-2 Control Valve 

In first gear the solenoid is OFF, the AFL fluid is blocked by the solenoid, and the 3-2 signal fluid exhausts 
through the solenoid and the spring force opens the 3-2 control valve.

 

2004 Hummer H2 

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

  

Fig. 474: Manual First Gear 
Courtesy of GENERAL MOTORS CORP.

 

2004 Hummer H2 

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

  

REVERSE 

When the gear selector lever is moved to the Reverse (R) position (from the Park position), the following 
changes occur to the transmissions hydraulic and electrical systems: 

Manual Valve 

The manual valve moves to the Reverse position and line pressure enters the reverse fluid circuit. As in Park, 
line pressure also fills the PR (Park/Reverse) fluid circuit. All other fluid circuits are blocked by the manual 
valve. 

Lo and Reverse Clutch 

As in Park, PR fluid pressure acts on the outer area of the lo and reverse clutch piston to apply the lo and 
reverse clutch. Also, Lo/reverse fluid from the lo overrun valve acts on the inner area of the piston to increase 
the holding capacity of the clutch (see Note below). 

Reverse Input Checkball (#3) 

Reverse fluid pressure seats the #3 checkball, flows through orifice #17 and fills the reverse input fluid circuit. 
This orifice helps control the reverse input clutch apply rate when engine speed is at idle. 

Reverse Abuse Valve 

Reverse fluid pressure acts on the end of the valve opposite of spring force. At engine speeds above idle, 
reverse fluid pressure, which is fed by line pressure, increases and moves the valve against spring force (as 
shown). Reverse fluid can then fill the reverse input fluid circuit through the reverse abuse valve. This bypasses 
the control of orifice #17 and provides a faster clutch apply. 

Boost Valve 

Reverse input fluid pressure moves the boost valve against the pressure regulator valve spring. The spring acts 
on the pressure regulator valve to increase the operating range of line pressure in Reverse. Reverse input fluid 
also flows through the valve and to the reverse input clutch piston. Remember that torque signal fluid pressure 
continually acts on the boost valve to control line pressure in response to vehicle operating conditions. 

Reverse Input Clutch Piston 

Reverse input fluid pressure moves the piston to apply the reverse input clutch plates and obtain Reverse. 

Reverse Input Air Bleed Checkball 

This ball and capsule is located in the reverse input fluid circuit in the oil pump to provide an air escape when 
the fluid pressure increases. It also allows air into the circuit to displace the fluid when the clutch releases. 

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly 

 

2004 Hummer H2 

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

  

Reverse input fluid pressure closes the normally open reverse switch in the TFP manual valve position switch 
This signals the PCM that the manual valve is in the Reverse (R) position. 

Shift Solenoid Valves (1-2 and 2-3) 

Both shift solenoid valves are energized as in the Park range. Signal A and signal B fluids are blocked from 
exhausting through the shift solenoid valves to maintain fluid pressure in these circuits at the end of the shift 
valves. 

Shift Valves (1-2, 2-3 and 3-4) 

Signal A fluid pressure holds the 1-2 shift valve in the downshifted position and the 3-4 shift valve in the 
upshifted (First and Fourth gear) position. Signal B fluid pressure from the 2-3 shift solenoid valve holds the 2-
3 shift valve train in the downshifted position. 

Pressure Control (PC) Solenoid Valve 

The PC solenoid valve continues to regulate AFL fluid into torque signal fluid pressure. The PCM varies the 
current at the solenoid to regulate torque signal fluid pressure in response to throttle position and other PCM 
input signals. Torque signal fluid pressure is used to control line pressure at the boost and pressure regulator 
valves. 

Note: The explanation in each gear range is, for the most part, limited.

 

2004 Hummer H2 

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