Fig. 495: Manual Third Gear Hydraulic Circuit Diagram
Courtesy of GENERAL MOTORS CORP.
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
2007 Hummer H3
2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3