RAM 3500 HD Truck 4WD L6-6.7L DSL Turbo VIN A (2007)
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Aid in quality of the 1-2 upshift.
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Aid in the quality and timing of the 3-2 kickdown ranges.
When the manual valve is set to the DRIVE position and the transmission is in the first or second gear range, 1-2 shift control or "modulated throttle
pressure" is supplied to the middle of the accumulator piston by the 1-2 shift control valve. During the 1-2 upshift, this pressure is used to control the
kickdown servo apply pressure that is needed to apply the kickdown and accumulator pistons. Thus, the 1-2 shift point is "cushioned" and the quality is
improved. During a WOT kickdown, kickdown pressure is applied between the kickdown valve and the 1-2 shift control valve. This additional pressure
is directed to the 1-2 shift control's spring cavity, adding to the spring load on the valve. The result of this increased "modulated" throttle pressure is a
firmer WOT upshift.
2-3 SHIFT VALVE
2-3 Shift Valve - Before Shift
The 2-3 shift valve mechanism consists of the 2-3 shift valve, governor plug and spring, and a throttle plug. After the 1-2 shift valve has completed its
operation and applied the front band, line pressure is directed to the 2-3 shift valve through the connecting passages from the 1-2 shift valve. The line
pressure will then dead-end at land #2 until the 2-3 valve is ready to make its shift. Now that the vehicle is in motion and under acceleration, there is
throttle pressure being applied to the spring side of the valve and between lands #3 and #4.
2-3 Shift Valve - After Shift
As vehicle speed increases, governor pressure increases proportionately, until it becomes great enough to overcome the combined throttle and spring
pressure on the right side of the valve. Since the throttle pressure end of the 2-3 shift valve is larger in diameter than the 1-2 shift valve, the 2-3 shift will
always happen at a greater speed than the 1-2 shift. When this happens, the governor plug is forced against the shift valve moving it to the right. The shift
valve causes land #4 to close the passage supplying throttle pressure to the 2-3 shift valve. Without throttle pressure present in the circuit now, the
