Dodge Dakota (R1). Manual — part 644
Meanwhile, the torque converter is filled slowly. In
all other gear positions (Fig. 265), fluid flows
between two right side lands to the switch valve and
torque converter. At low pump speeds, the flow is
controlled by the pressure valve groove to reduce
pressure to the torque converter. After the torque
converter and switch valve fill with fluid, the switch
valve becomes the controlling metering device for
torque converter pressure. The regulator valve then
begins to control the line pressure for the other
transmission circuits. The balance of the fluid pres-
sure pushing the valve to the right and the spring
pressure pushing to the left determines the size of
the metering passage at land #2 (land #1 being at
the far right of the valve in the diagram). As fluid
leaks past the land, it moves into a groove connected
to the filter or sump. As the land meters the fluid to
the sump, it causes the pressure to reduce and the
spring decreases the size of the metering passage.
When the size of the metering passage is reduced,
the pressure rises again and the size of the land is
increased again. Pressure is regulated by this con-
stant balance of hydraulic and spring pressure.
The metering at land #2 establishes the line pres-
sure throughout the transmission. It is varied accord-
ing
to
changes
in
throttle
position
and
the
transmission’s internal condition within a range of
57-94 psi (except in REVERSE) (Fig. 266). The regu-
lated line pressure in REVERSE (Fig. 267) is held at
much higher pressures than in the other gear posi-
tions:
145-280
psi.
The
higher
pressure
for
REVERSE is achieved by the manual valve blocking
the supply of line pressure to the reaction area left of
land #4. With this pressure blocked, there is less
area for pressure to act on to balance the force of the
spring on the right. This allows line pressure to push
the valve train to the right, reducing the amount of
fluid returned to the pump’s inlet, increasing line
pressure.
Fig. 265 Regulator Valve in NEUTRAL Position
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AUTOMATIC TRANSMISSION - 42RE
AN
VALVE BODY (Continued)
Fig. 266 Regulator Valve in DRIVE Position
Fig. 267 Regulator Valve in REVERSE Position
AN
AUTOMATIC TRANSMISSION - 42RE
21 - 221
VALVE BODY (Continued)
KICKDOWN VALVE
When the throttle valve is as far over to the left as
it can go, the maximum line pressure possible will
enter the throttle pressure circuit. In this case, throt-
tle pressure will equal line pressure. With the kick-
down valve (Fig. 268) pushed into the bore as far as
it will go, fluid initially flows through the annular
groove of the 2-3 shift valve (which will be in the
direct drive position to the right).
After passing the annular groove, the fluid is
routed to the spring end of the 2-3 shift valve. Fluid
pressure reacting on the area of land #1 overcomes
governor pressure, downshifting the 2-3 shift valve
into the kickdown, or second gear stage of operation.
The valve is held in the kickdown position by throttle
pressure routed from a seated check ball (#2). Again,
if vehicle speed is low enough, throttle pressure will
also push the 1-2 shift valve left to seat its governor
plug, and downshift to drive breakaway.
Fig. 268 Kickdown Valve-Wide Open Throttle
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AUTOMATIC TRANSMISSION - 42RE
AN
VALVE BODY (Continued)
KICKDOWN LIMIT VALVE
The purpose of the limit valve is to prevent a 3-2
downshift at higher speeds when a part-throttle
downshift is not desirable. At these higher speeds
only a full throttle 3-2 downshift will occur. At low
road speeds (Fig. 269) the limit valve does not come
into play and does not affect the downshifts. As the
vehicle’s speed increases (Fig. 270), the governor
pressure also increases. The increased governor pres-
sure acts on the reaction area of the bottom land of
the limit valve overcoming the spring force trying to
push the valve toward the bottom of its bore. This
pushes the valve upward against the spring and bot-
toms the valve against the top of the housing. With
the valve bottomed against the housing, the throttle
pressure supplied to the valve will be closed off by
the bottom land of the limit valve. When the supply
of throttle pressure has been shut off, the 3-2 part
throttle downshift plug becomes inoperative, because
no pressure is acting on its reaction area.
Fig. 269 Kickdown Limit Valve-Low Speeds
Fig. 270 Kickdown Limit Valve-High Speeds
AN
AUTOMATIC TRANSMISSION - 42RE
21 - 223
VALVE BODY (Continued)
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