RAM 2500 Van V8-5.2L Prop VIN 2 (2000)
The valve has two specific operations (Fig. 31):
-
Aid in quality of the 1-2 upshift.
-
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
Fig. 32
The 2-3 shift valve mechanism (Fig. 32) 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.
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. 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 governor
plug will push the valve over far enough to bottom the valve in its bore. This allows land #2 to direct line pressure to the front clutch.
