Dodge RAM 1500 1998 Owner's Manual page 1977

21 - 274 AUTOMATIC TRANSMISSION - 48RE
VALVE BODY (Continued)
Meanwhile, the torque converter is filled slowly. In
all other gear positions (Fig. 254), 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.
Fig. 254 Regulator Valve in Neutral Position
The metering at land #2 establishes the line pres-
sure throughout the transmission. It is varied accord-
ing to changes in
transmission's internal condition within a range of
57-94 psi (except in REVERSE) (Fig. 255). The regu-
lated line pressure in REVERSE (Fig. 256) is held at
much higher pressures than in the other gear posi-
tions: 145-280 psi.
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.
throttle position and
The higher pressure
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the
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