Forward Clutch Accumulator Checkball (#12)
D4 fluid pressure seats the checkball and is orificed (#22) into the forward clutch feed fluid
circuit. This orifice helps control the forward clutch apply rate.
Forward Clutch Accumulator Piston
Forward clutch feed fluid pressure moves the piston against spring force. This action absorbs
some of the initial increase of forward clutch feed fluid pressure to cushion the forward clutch
apply.
Forward Clutch Abuse Valve
D4 fluid pressure acts on the valve opposite of spring force. At engine speeds greater than idle,
D4 fluid pressure increases and moves the valve against spring force (as shown). D4 fluid can
then quickly fill the forward clutch feed fluid circuit, thereby bypassing the control of orifice #22
and providing a faster apply of the forward clutch. Otherwise, with increased throttle opening
and engine torque, the clutch may slip during apply.
Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly
D4 fluid pressure is routed to the TFP manual valve position switch and closes the normally open
D4 fluid pressure switch. This signals the PCM that the transmission is operating in Overdrive
range.
1-2 Shift Solenoid (SS) Valve
Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal A fluid
from exhausting through the solenoid. This maintains pressure in the signal A fluid circuit.
2-3 Shift Solenoid (SS) Valve
Energized (ON) as in Neutral, the normally open solenoid is closed and 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.
2-3 Shift Valve Train
Signal B fluid pressure at the solenoid end of the 2-3 shift valve holds the valve train in the
downshifted position against AFL fluid pressure acting on the 2-3 shift valve. In this position, the
2-3 shuttle valve blocks 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
2007 Hummer H3
2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3