Jeep cherokee 2000 Service Manual page 1019

XJ
DESCRIPTION AND OPERATION (Continued)
shift control valve. This additional pressure is
directed to the 1–2 shift control's spring cavity, add-
ing to the spring load on the valve. The result of this
increased "modulated" throttle pressure is a firmer
WOT upshift.
SHUTTLE VALVE
The assembly is contained in a bore in the valve
body above the shift valves. When the manual valve
is positioned in the Drive range, throttle pressure
acts on the throttle plug of the shuttle valve (Fig. 29)
to move it against a spring, increasing the spring
force on the shuttle valve. During a part or full throt-
tle 1–2 upshift, the throttle plug is bottomed by
throttle pressure, holding the shuttle valve to the
right against governor pressure, and opening a
by–pass circuit. The shuttle valve controls the qual-
ity of the kickdown shift by restricting the rate of
1 – THROTTLE PLUG
AUTOMATIC TRANSMISSION—30RH
fluid discharge from the front clutch and servo
release circuits. During a 3–2 kickdown, fluid dis-
charges through the shuttle by–pass circuit. When
the shuttle valve closes the by–pass circuit, fluid dis-
charge is restricted and controlled for the application
of the front band. During a 2–3 "lift foot" upshift, the
shuttle valve by–passes the restriction to allow full
fluid flow through the by–pass groove for a faster
release of the band.
2–3 SHIFT VALVE
The 2–3 shift valve mechanism (Fig. 30) 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 pres-
sure 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
Fig. 29 1–2 Shift Control Valve
2 – SHUTTLE VALVE
3 – 1-2 SHIFT CONTROL VALVE
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