1–2 Shift Control Valve; 1–2 Shift Valve-After Shift - Jeep 200 Cherokee Service Manual

21 - 110 AUTOMATIC TRANSMISSION—30RH
DESCRIPTION AND OPERATION (Continued)
1 – TO FRONT SERVO AND 2-3 SHIFT VALVE
2 – THROTTLE PRESSURE
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 pres-
sure to the right side of the valve. When the throttle
pressure is closed off, the valve will move even far-
ther to the right, allowing line pressure to enter
another circuit and energize the front servo, applying
the front band (Fig. 28).
The governor plug serves a dual purpose: [0001]
• It allows the shift valves to move either left or
right, allowing both upshifts and downshifts.
• 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
Fig. 28 1–2 Shift Valve-After Shift
3 – LINE PRESSURE
4 – LINE PRESSURE PASSAGE FOR MANUAL LOW POSITION
plate overcoming governor pressure. With the combi-
nation 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. 29):
• Aid in quality of the 1–2 upshift.
• 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 pres-
sure" 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 kick-
down 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
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