Dodge RAM 1500 1998 Owner's Manual page 1970

DR
TRANSMISSION
TEMPERATURE SENSOR
DESCRIPTION
Transmission fluid temperature readings are sup-
plied to the transmission control module by the ther-
mistor (Fig. 248). The temperature readings are used
to control engagement of the fourth gear overdrive
clutch, the converter clutch, and governor pressure.
Normal resistance value for the thermistor at room
temperature is approximately 2000 ohms.
The thermistor is part of the governor pressure
sensor assembly and is immersed in transmission
fluid at all times.
Fig. 248 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
OPERATION
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10°C (50°F).
If fluid temperature exceeds 126°C (260°F), the
PCM causes a 4-3 downshift and engage the con-
verter clutch. Engagement is according to the third
gear converter clutch engagement schedule.
The Tow/Haul lamp in the instrument panel illumi-
nates when the shift back to third occurs. The trans-
mission will not allow fourth gear operation until
fluid temperature decreases to approximately 110°C
(230°F).
AUTOMATIC TRANSMISSION - 48RE
VALVE BODY
DESCRIPTION
The valve body consists of a cast aluminum valve
body, a separator plate, and transfer plate. The valve
body contains valves and check balls that control
fluid delivery to the torque converter clutch, bands,
and frictional clutches. The valve body contains the
following components (Fig. 249), (Fig. 250), (Fig.
251), and (Fig. 252):
• Regulator valve
• Regulator valve throttle pressure plug
• Line pressure sleeve
• Kickdown valve
• Kickdown limit valve
• 1-2 shift valve
• 1-2 control valve
• 2-3 shift valve
• 2-3 governor plug
• 3-4 shift valve
• 3-4 timing valve
• 3-4 quick fill valve
• 3-4 accumulator
• Throttle valve
• Throttle pressure plug
• Switch valve
• Manual valve
• Converter clutch lock-up valve
• Converter clutch lock-up timing Valve
• Shuttle valve
• Shuttle valve throttle plug
• Boost Valve
• 9 check balls
By adjusting the spring pressure acting on the reg-
ulator valve, transmission line pressure can be
adjusted.
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