Dakota 2WD L4-2.5L VIN P (2001)
manual valve has been placed into a forward gear range line pressure is directed to the 1-2 shift valve. As the throttle is depressed, throttle pressure is
applied to the right side of the 1-2 shift valve assembly. With throttle pressure applied to the right side of the valve, there is now both spring pressure
and throttle pressure acting on the valve, holding it against the governor plug. As the vehicle begins to move and build speed, governor pressure is
created and is applied to the left of the valve at the Governor plug. When governor pressure builds to a point where it can overcome the combined
force of the spring and throttle pressure on the other side of the valve, the valve will begin to move over to the right. As the valve moves to the right,
the middle land of the valve will close off the circuit supplying the throttle pressure to the right side of the valve. When the throttle pressure is closed
off, the valve will move even farther to the right, allowing line pressure to enter another circuit and energize the front servo, applying the front band
(Fig. 272).
The governor plug serves a dual purpose:
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It allows the shift valves to move either left or right, allowing both upshifts and downshifts.
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When in a manual selection position, it will be hydraulically "blocked" into position so no upshift can occur. The physical blocking of the upshift
while in the manual "1" position is accomplished by the directing of line pressure between both lands of the governor plug. The line pressure
reacts against the larger land of the plug, pushing the plug back against the end plate overcoming governor pressure. With the combination of the
line pressure and spring pressure, the valve cannot move, preventing any upshift.
1-2 SHIFT CONTROL VALVE
It contains a valve with four lands and a spring. It is used as both a "relay" and "balanced" valve. The valve has two specific operations (Fig. 273):
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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 kick-down 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
kick-down 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
