torque DODGE RAM 1500 1998 2.G Workshop Manual

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.
OPERATION
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10ÉC (50ÉF).
If fluid temperature exceeds 126ÉC (260ÉF), 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 110ÉC
(230ÉF).
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):
²Regulator valve
²Regulator valve throttle pressure plug
²Line pressure sleeve
²Kickdown valve
²Kickdown limit valve
²1-2 shift valve
²1-2 control valve
²2-3 shift valve
²2-3 governor plug
²3-4 shift valve
²3-4 timing valve
²3-4 quick fill valve
²3-4 accumulator
²Throttle valve
²Throttle pressure plug
²Switch valve
²Manual valve
²Converter clutch lock-up valve
²Converter clutch lock-up timing Valve
²Shuttle valve
²Shuttle valve throttle plug
²Boost Valve
²9 check balls
By adjusting the spring pressure acting on the reg-
ulator valve, transmission line pressure can be
adjusted.
Fig. 248 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 267

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.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. 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. 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. 254 Regulator Valve in Neutral Position
21 - 274 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

pressure is ªmeteredº out into the circuits and viewed
as throttle pressure. This increased throttle pressure
is metered out into the circuits it is applied to: the
1-2 and 2-3 shift valves. When the throttle pressure
is high enough, a 3-2 downshift will occur. If the
vehicle speed is low enough, a 2-1 downshift will
occur.
SWITCH VALVE
When the transmission is in Drive Second before
the TCC application occurs (Fig. 268), the pressure
regulator valve is supplying torque converter pres-
sure to the switch valve. The switch valve directs
this pressure through the transmission input shaft,
into the converter, through the converter, back outbetween the input shaft and the reaction shaft, and
back up to the switch valve. From the switch valve,
the fluid pressure is directed to the transmission
cooler, and lubrication pressure returns from the
cooler to lubricate different portions of the transmis-
sion.
Fig. 268 Switch Valve - Torque Converter Unlocked
DRAUTOMATIC TRANSMISSION - 48RE 21 - 283
VALVE BODY (Continued)

Once the TCC control valve has moved to the right
(Fig. 269), line pressure is directed to the tip of the
switch valve, forcing the valve to the right. The
switch valve now vents oil from the front of the pis-
ton in the torque converter, and supplies line pres-
sure to the (rear) apply side of the torque converter
piston. This pressure differential causes the piston to
apply against the friction material, cutting off any
further flow of line pressure oil. After the switch
valve is shuttled right allowing line pressure to
engage the TCC, torque converter pressure is
directed past the switch valve into the transmission
cooler and lubrication circuits.
Fig. 269 Switch Valve - Torque Converter Locked
21 - 284 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

MANUAL VALVE
The manual valve (Fig. 270) is a relay valve. The
purpose of the manual valve is to direct fluid to the
correct circuit needed for a specific gear or driving
range. The manual valve, as the name implies, is
manually operated by the driver with a lever located
on the side of the valve body. The valve is connected
mechanically by either a cable or linkage to the gear-
shift mechanism. The valve is held in each of its
positions by a spring-loaded roller or ball that
engages the ªroostercombº of the manual valve lever.
CONVERTER CLUTCH LOCK-UP VALVE
The torque converter clutch (TCC) lock-up valve
controls the back (ON) side of the torque converter
clutch. When the PCM energizes the TCC solenoid to
engage the converter clutch piston, pressure is
applied to the TCC lock-up valve which moves to the
right and applies pressure to the torque converter
clutch.
CONVERTER CLUTCH LOCK-UP TIMING VALVE
The torque converter clutch (TCC) lock-up timing
valve is there to block any 4-3 downshift until the
TCC is completely unlocked and the clutch is disen-
gaged.
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.
262) to move it against a spring, increasing the
spring force on the shuttle valve. During a part or
full throttle 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
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 ªlift footº 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.
Fig. 270 Manual Valve
DRAUTOMATIC TRANSMISSION - 48RE 21 - 285
VALVE BODY (Continued)

BOOST VALVE
The boost valve (Fig. 271) provides increased fluid
apply pressure to the overdrive clutch during 3-4
upshifts (Fig. 272), and when accelerating in fourth
gear. The boost valve also serves to increase line
pressure during torque converter lock-up.
REMOVAL
The valve body can be removed for service without
having to remove the transmission assembly.
The valve body can be disassembled for cleaning
and inspection of the individual components.
The only replaceable valve body components are:
²Manual lever.
²Manual lever washer, seal, E-clip, and shaft
seal.
²Manual lever detent ball.
²Throttle lever.
²Fluid filter.
²Pressure adjusting screw bracket.
²Governor pressure solenoid.
²Governor pressure sensor (includes transmission
temperature thermistor).
²Converter clutch/overdrive solenoid assembly
and harness.
²Governor housing gasket.
²Solenoid case connector O-rings.
(1) Shift transmission into NEUTRAL.
(2) Raise vehicle.
(3) Remove gearshift and throttle levers from shaft
of valve body manual lever.
(4) Disconnect wires at solenoid case connector
(Fig. 273).
(5) Remove the transmission range sensor (Refer
to 21 - TRANSMISSION/AUTOMATIC/TRANSMIS-
SION RANGE SENSOR - REMOVAL).
(6) Position drain pan under transmission oil pan.
(7) Remove transmission oil pan and gasket.
(8) Remove fluid filter from valve body.
(9) Remove bolts attaching valve body to transmis-
sion case.
(10) Lower valve body enough to remove accumu-
lator piston and springs.
Fig. 273 Transmission Case Connector
1 - SOLENOID CASE CONNECTOR
2 - TRANSMISSION RANGE SENSOR
Fig. 271 Boost Valve Before Lock-up
Fig. 272 Boost Valve After Lock-up
21 - 286 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

Check the two separator plates for distortion or
damage of any kind. Inspect the upper housing,
lower housing, 3-4 accumulator housing, and transfer
plate carefully. Be sure all fluid passages are clean
and clear. Check condition of the upper housing and
transfer plate check balls as well. The check balls
and ball seats must not be worn or damaged.
Trial fit each valve and plug in its bore to check
freedom of operation. When clean and dry, the valves
and plugs should drop freely into the bores.
Valve body bores do not change dimensionally with
use. If the valve body functioned correctly when new,
it will continue to operate properly after cleaning and
inspection. It should not be necessary to replace a
valve body assembly unless it is damaged in han-
dling.
The only serviceable valve body components are
listed below. The remaining valve body components
are serviced only as part of a complete valve body
assembly. Serviceable parts are:
²dual solenoid and harness assembly
²solenoid gasket
²solenoid case connector O-rings and shoulder
bolt
²switch valve and spring
²pressure adjusting screw and bracket assembly
²throttle lever
²manual lever and shaft seal
²throttle lever shaft seal, washer, and E-clip
²fluid filter and screws
²detent ball and spring
²valve body screws
²governor pressure solenoid
²governor pressure sensor and retaining clip
²park lock rod and E-clipASSEMBLY
CAUTION: Do not force valves or plugs into place
during reassembly. If the valve body bores, valves
and plugs are free of distortion or burrs, the valve
body components should all slide into place easily.
In addition, do not overtighten the transfer plate
and valve body screws during reassembly. Over-
tightening can distort the housings resulting in
valve sticking, cross leakage and unsatisfactory
operation. Tighten valve body screws to recom-
mended torque only.
LOWER HOUSING
(1) Lubricate valves, springs, and the housing
valve and plug bores with clean transmission fluid
(Fig. 305).
(2) Install 3-4 timing valve spring and valve in
lower housing.
(3) Install 3-4 quick fill valve in lower housing.
(4) Install 3-4 quick fill valve spring and plug in
housing.
(5) Install timing valve end plate. Tighten end
plate screws to 4 N´m (35 in. lbs.) torque.
DRAUTOMATIC TRANSMISSION - 48RE 21 - 299
VALVE BODY (Continued)

3-4 ACCUMULATOR
(1) Lubricate accumulator piston, seals and hous-
ing piston bore with clean transmission fluid (Fig.
306).
(2) Install new seal rings on accumulator piston.
(3) Install piston and spring in housing.
(4) Install end plate on housing.
TRANSFER PLATE
(1) Install rear clutch and rear servo check balls in
transfer plate (Fig. 307).
(2) Install filter screen in upper housing separator
plate (Fig. 308).
(3) Align and position upper housing separator
plate on transfer plate (Fig. 309).
(4) Install brace plate (Fig. 309). Tighten brace
attaching screws to 4 N´m (35 in. lbs.) torque.
(5) Install remaining separator plate attaching
screws. Tighten screws to 4 N´m (35 in. lbs.) torque.
Fig. 306 3-4 Accumulator and Housing
1 - ACCUMULATOR PISTON
2 - 3-4 ACCUMULATOR HOUSING
3 - TEFLON SEALS
4 - PISTON SPRING
5 - COVER PLATE AND SCREWS
Fig. 307 Rear Clutch And Rear Servo Check Ball
Locations
1 - REAR CLUTCH CHECK BALL
2 - REAR SERVO CHECK BALL
3 - TRANSFER PLATE
Fig. 308 Separator Plate Filter Screen Installation
1 - UPPER HOUSING SEPARATOR PLATE
2 - FILTER SCREEN
Fig. 309 Brace Plate
1 - BRACE
2 - TRANSFER PLATE
3 - SEPARATOR PLATE
DRAUTOMATIC TRANSMISSION - 48RE 21 - 301
VALVE BODY (Continued)

(5) Install lower housing on assembled transfer
plate and upper housing (Fig. 314).
(6) Install and start all valve body screws by hand
except for the screws to hold the boost valve tube
brace. Save those screws for later installation. Then
tighten screws evenly to 4 N´m (35 in. lbs.) torque.
Start at center and work out to sides when tighten-
ing screws (Fig. 314).
UPPER HOUSING VALVE AND PLUG
Refer to (Fig. 315), (Fig. 316) and (Fig. 317) to per-
form the following steps.
(1) Lubricate valves, plugs, springs with clean
transmission fluid.
(2) Assemble regulator valve line pressure sleeve,
throttle plug and spring. Insert assembly in upper
housing and install cover plate. Tighten cover plate
screws to 4 N´m (35 in. lbs.) torque.
(3) Install 1-2 and 2-3 shift valves and springs.
(4) Install 1-2 shift control valve and spring.
Fig. 314 Installing Lower Housing On Transfer Plate
And Upper Housing
1 - VALVE BODY SCREWS (13)
2 - LOWER HOUSING
3 - UPPER HOUSING
4 - TRANSFER PLATE
Fig. 315 Shuttle and Boost Valve Locations
1 - SPRING 8 - SHUTTLE VALVE COVER
2 - RETAINER 9 - SHUTTLE VALVE
3 - BOOST VALVE 10 - SHUTTLE VALVE PRIMARY SPRING
4 - BOOST VALVE PLUG 11 - GOVERNOR PLUG COVER
5 - SPRING GUIDES 12 - THROTTLE PLUG
6 - E-CLIP 13 - UPPER HOUSING
7 - SHUTTLE VALVE SECONDARY SPRING 14 - BOOST VALVE COVER
DRAUTOMATIC TRANSMISSION - 48RE 21 - 303
VALVE BODY (Continued)

(5) Install retainer, spring, limit valve, and 2-3
throttle plug from limit valve housing.
(6) Install limit valve housing and cover plate.
Tighten screws to 4 N´m (35 in. lbs.).
(7) Install shuttle valve as follows:
(a) Insert plastic guides in shuttle valve second-
ary spring and install spring on end of valve.
(b) Install shuttle valve into housing.
(c) Hold shuttle valve in place.
(d) Compress secondary spring and install E-clip
in groove at end of shuttle valve.(e) Verify that spring and E-clip are properly
seated before proceeding.
(8) Install shuttle valve cover plate. Tighten cover
plate screws to 4 N´m (35 in. lbs.) torque.
(9) Install 1-2 and 2-3 valve governor plugs in
valve body.
(10) Install shuttle valve primary spring and
throttle plug.
(11) Align and install governor plug cover. Tighten
cover screws to 4 N´m (35 in. lbs.) torque.
Fig. 316 Upper Housing Control Valve Locations
1 - UPPER HOUSING 8 - MANUAL VALVE
2 - REGULATOR VALVE 9 - 1-2 GOVERNOR PLUG
3 - SWITCH VALVE 10 - GOVERNOR PLUG COVER
4 - REGULATOR VALVE SPRING 11 - THROTTLE PLUG
5 - KICKDOWN VALVE 12 - 2-3 GOVERNOR PLUG
6 - KICKDOWN DETENT 13 - SHUTTLE VALVE PRIMARY SPRING
7 - THROTTLE VALVE AND SPRING
21 - 304 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)