Trans temp DODGE RAM 1500 1998 2.G Workshop Manual

(1) Apply a light coat of Mopar high temperature
bearing grease or equivalent to contact surfaces of
following components:
²input shaft splines.
²release bearing slide surface of front retainer.
²release bearing bore.
²release fork.
²release fork ball stud.
²propeller shaft slip yoke.
(2) Apply sealer to threads of bottom PTO cover
bolt and install bolt in case.
(3) Mount transmission on jack and position trans-
mission under vehicle.
(4) Raise transmission until input shaft is centered
in clutch disc hub.
(5) Move transmission forward and start input
shaft in clutch disc and pilot bushing/bearing.
(6)
Work transmission forward until seated against
engine block. Do not allow transmission to remain
unsupported after input shaft has entered clutch disc.
(7) Install and tighten transmission-to-engine
block bolts.
(8) Install clutch slave cylinder.
(9) Connect backup light switch wires.
(10) Position transmission harness wires in clips
on transmission.
(11) Install transmission mount on transmission or
rear crossmember.
(12) Install rear crossmember.
(13) Remove transmission jack and engine support
fixture.
(14)
Fill transmission with required lubricant (Fig.
96). Check lubricant level in transfer case if equipped.
TWO WHEEL DRIVE
(1) Install propeller shaft with referece marks
aligned.
(2) Install exhaust system components.(3) Remove support and lower vehicle.
(4) Shift transmission into third gear.
(5) Clean the mating surfaces of shift tower and
isolator plate with suitable wax and grease remover.
(6) Apply Mopar Gasket Maker or equivalent to
sealing surface of the transmission case. Do not over
apply sealant.
(7) Install isolator plate onto the transmission case
metal side down.
(8) Install shift tower onto the isolator plate. No
sealant is necessary between the shift tower and top
of isolator plate.
(9) Verify shift tower, isolator plate and the shift
socket are properly aligned.
(10) Install bolts to hold the shift tower to the iso-
lator plate and the transmission case. Tighten bolts
to 10.2±11.25 N´m (7.5±8.3 ft. lbs.).
(11) Install shift boot and bezel.
FOUR WHEEL DRIVE
(1) Install and secure transfer case on the trans-
mission jack.
(2) Raise and align transfer case input gear with
transmission mainshaft.
(3) Move transfer case forward and seat it on
adapter.
(4)
Install and tighten transfer case mounting nuts to
41-47 N´m (30-35 ft. lbs.) if case has 3/8 studs. If case
has 5/16 studs tighten to 30-41 N´m (22-30 ft. lbs.).
(5) Connect transfer case shift lever to range lever
on transfer case.
(6) Install propeller shafts with reference marks
aligned.
(7) Install transfer case skid plate, if equipped,
and crossmember. Tighten attaching bolts/nuts to 41
N´m (30 ft. lbs.).
(8) Install exhaust system components.
(9) Remove support and lower vehicle.
(10) Shift transmission into third gear.
(11) Clean the mating surfaces of shift tower, iso-
lator plate and transmission case with suitable wax
and grease remover.
(12) Apply Mopar Gasket Maker or equivalent to
the sealing surface of the transmission case. Do not
over apply sealant.
(13) Install isolator plate onto the transmission
case, metal side down.
(14) Install shift tower onto the isolator plate. No
sealant is necessary between the shift tower and top
of isolator plate.
(15) Verify that the shift tower, isolator plate and
the shift tower bushings are properly aligned.
(16) Install the bolts to hold the shift tower to the
isolator plate and the transmission case. Tighten the
shift tower bolts to 10.2-11.25 N´m (7.5-8.3 ft. lbs.).
(17) Install shift lever boot and bezel.
Fig. 96 FILL PLUG
1 - FILL PLUG
21 - 122 MANUAL TRANSMISSION - NV5600DR
MANUAL TRANSMISSION - NV5600 (Continued)

OUTPUT SHAFT FRONT BEARING
REMOVAL............................216
INSTALLATION........................216
OUTPUT SHAFT REAR BEARING
REMOVAL............................216
INSTALLATION........................217
OVERDRIVE CLUTCH
DESCRIPTION........................217
OPERATION..........................217
OVERDRIVE UNIT
REMOVAL............................218
DISASSEMBLY........................218
CLEANING...........................225
INSPECTION.........................225
ASSEMBLY...........................226
INSTALLATION........................235
OVERRUNNING CLUTCH CAM/OVERDRIVE
PISTON RETAINER
DESCRIPTION........................236
OPERATION..........................236
DISASSEMBLY........................236
CLEANING...........................236
INSPECTION.........................237
ASSEMBLY...........................237
PISTONS
DESCRIPTION........................239
OPERATION..........................239
PLANETARY GEARTRAIN/OUTPUT SHAFT
DESCRIPTION........................241
OPERATION..........................241
DISASSEMBLY........................242
INSPECTION.........................243
ASSEMBLY...........................244
REAR CLUTCH
DESCRIPTION........................247
OPERATION..........................248
DISASSEMBLY........................248
CLEANING...........................248
INSPECTION.........................248
ASSEMBLY...........................249
REAR SERVO
DESCRIPTION........................251
OPERATION..........................251
DISASSEMBLY........................251
CLEANING...........................251
ASSEMBLY...........................251
SHIFT MECHANISM
DESCRIPTION........................252OPERATION..........................252
SOLENOID
DESCRIPTION........................252
OPERATION..........................252
SPEED SENSOR
DESCRIPTION........................253
OPERATION..........................253
THROTTLE VALVE CABLE
DESCRIPTION........................253
ADJUSTMENTS - THROTTLE VALVE CABLE . 254
TORQUE CONVERTER
DESCRIPTION........................255
OPERATION..........................259
REMOVAL............................260
INSTALLATION........................260
TORQUE CONVERTER DRAINBACK VALVE
DESCRIPTION........................261
OPERATION..........................261
STANDARD PROCEDURE - TORQUE
CONVERTER DRAINBACK VALVE........261
TOW/HAUL OVERDRIVE SWITCH
DESCRIPTION........................261
OPERATION..........................262
DIAGNOSIS AND TESTING - OVERDRIVE
ELECTRICAL CONTROLS..............262
REMOVAL............................262
INSTALLATION........................262
TRANSMISSION RANGE SENSOR
DESCRIPTION........................263
OPERATION..........................263
DIAGNOSIS AND TESTING - TRANSMISSION
RANGE SENSOR (TRS)................264
REMOVAL............................265
INSTALLATION........................266
TRANSMISSION TEMPERATURE SENSOR
DESCRIPTION........................267
OPERATION..........................267
VALVE BODY
DESCRIPTION........................267
OPERATION..........................272
REMOVAL............................286
DISASSEMBLY........................287
CLEANING...........................298
INSPECTION.........................298
ASSEMBLY...........................299
INSTALLATION........................309
ADJUSTMENTS - VALVE BODY...........310
DRAUTOMATIC TRANSMISSION - 48RE 21 - 131

IDENTIFICATION
Transmission identification numbers are stamped
on the left side of the case just above the oil pan gas-
ket surface (Fig. 2). Refer to this information when
ordering replacement parts.
GEAR RATIOS
The 48RE gear ratios are:
1st.................................2.45:1
2nd................................1.45:1
3rd................................1.00:1
4th.................................0.69:1
Rev.................................2.20:1
OPERATION
The application of each driving or holding compo-
nent is controlled by the valve body based upon the
manual lever position, throttle pressure, and gover-
nor pressure. The governor pressure is a variable
pressure input to the valve body and is one of the
signals that a shift is necessary. First through fourth
gear are obtained by selectively applying and releas-
ing the different clutches and bands. Engine power is
thereby routed to the various planetary gear assem-
blies which combine with the overrunning clutch
assemblies to generate the different gear ratios. The
torque converter clutch is hydraulically applied and
is released when fluid is vented from the hydraulic
circuit by the torque converter control (TCC) solenoid
on the valve body. The torque converter clutch is con-
trolled by the Powertrain Control Module (PCM). The
torque converter clutch engages in fourth gear, and
in third gear under various conditions, such as when
the O/D switch is OFF, when the vehicle is cruising
on a level surface after the vehicle has warmed up.
The torque converter clutch can also be engaged in
the MANUAL SECOND gear position if high trans-
mission temperatures are sensed by the PCM. The
torque converter clutch will disengage momentarily
when an increase in engine load is sensed by the
PCM, such as when the vehicle begins to go uphill or
the throttle pressure is increased. The torque con-
verter clutch feature increases fuel economy and
reduces the transmission fluid temperature.
Since the overdrive clutch is applied in fourth gear
only and the direct clutch is applied in all ranges
except fourth gear, the transmission operation for
park, neutral, and first through third gear will be
described first. Once these powerflows are described,
the third to fourth shift sequence will be described.
1 - TORQUE CONVERTER 10 - OVERDRIVE CLUTCH
2 - INPUT SHAFT 11 - DIRECT CLUTCH
3 - OIL PUMP 12 - PLANETARY GEAR
4 - FRONT BAND 13 - INTERMEDIATE SHAFT
5 - FRONT CLUTCH 14 - OVERDRIVE OVERRUNNING CLUTCH
6 - REAR CLUTCH 15 - DIRECT CLUTCH SPRING
7 - PLANETARIES 16 - OVERDRIVE PISTON RETAINER
8 - REAR BAND 17 - OIL PAN
9 - OVERRUNNING CLUTCH 18 - VALVE BODY
Fig. 2 Transmission Part Number And Serial
Number Location
1 - PART NUMBER
2 - BUILD DATE
3 - SERIAL NUMBER
21 - 134 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

(27) Note that overrunning clutch race will remain
on splines of low-reverse drum after removal (Fig.
36).The race is a permanent press fit on the
hub splines. Do not attempt to remove the race.
(28) Remove overrunning clutch assembly (Fig.
37). Assembly can be removed without displacing
rollers and springs if care is exercised. Note position
of rollers and springs for assembly reference.
(29) Remove rear band adjusting lever and reac-
tion pin.
(30) Remove rear band.
(31) Compress front servo rod guide with large
C-clamp and Tool C-4470, or Compressor Tool
C-3422-B (Fig. 38). Compress guide only enough to
permit snap-ring removal (about 1/8 in.).
(32) Remove servo piston snap-ring (Fig. 38).
Unseat one end of ring. Then carefully work removal
tool around back of ring until free of ring groove.
Exercise caution when removing snap-ring.
Servo bore can be scratched or nicked if care is
not exercised.
Fig. 38 Front Servo Retaining Snap-Ring
1 - C-CLAMP
2 - FRONT SERVO ROD GUIDE
3 - SNAP-RING
4 - TOOL C-4470
Fig. 36 Overrunning Clutch Race Position On
Low-Reverse Drum
1 - OVERRUNNING CLUTCH RACE
2 - LOW-REVERSE DRUM
Fig. 37 Overrunning Clutch
1 - CLUTCH CAM
2 - OVERRUNNING CLUTCH ASSEMBLY
DRAUTOMATIC TRANSMISSION - 48RE 21 - 165
AUTOMATIC TRANSMISSION - 48RE (Continued)

(9) Install the two screws to hold the TRS to the
mounting bracket. Tighten the screws to 5 N´m (45
in.lbs.).
(10) Verify proper sensor operation (Fig. 62).
(11) Move the transmission manual shaft lever to
the PARK position.
(12) Install torque converter. Use C-clamp or metal
strap to hold converter in place for installation.
BAND ADJUSTMENT AND FINAL
(1) Adjust front and rear bands as follows:
(a) Loosen locknut on each band adjusting screw
4-5 turns.
(b) Tighten both adjusting screws to 8 N´m (72
in. lbs.).
(c) Back off front band adjusting screw 1-3/4
turns.
(d) Back off rear band adjusting screw 3 turns.
(e) Hold each adjusting screw in position and
tighten locknut to 34 N´m (25 ft. lbs.) torque.
(2) Install magnet in oil pan. Magnet seats on
small protrusion at corner of pan.
(3) Position new oil pan gasket on case and install
oil pan. Tighten pan bolts to 13.6 N´m (125 in. lbs.).
(4) Install throttle valve and shift selector levers
on valve body manual lever shaft.
(5) Apply small quantity of dielectric grease to ter-
minal pins of solenoid case connector and neutral
switch.
(6) Fill transmission with recommended fluid.
INSTALLATION
(1) Check torque converter hub inner and outer
diameters and hub drive notches for sharp edgesburrs, scratches, or nicks. Polish the hub and notches
with 320/400 grit paper and crocus cloth if necessary.
The hub must be smooth to avoid damaging pump
seal at installation.
(2) Lubricate pocket in the rear oil pump seal lip
with transmission fluid.
(3) Lubricate converter pilot hub of the crankshaft
with a light coating of MopartHigh Temp Grease.
(4) Align and install converter in oil pump.
(5) Carefully insert converter in oil pump. Then
rotate converter back and forth until fully seated in
pump gears.
(6) Check converter seating with steel scale and
straightedge (Fig. 63). Surface of converter lugs
should be 19mm (0.75 in.) to rear of straightedge
when converter is fully seated.
(7) Temporarily secure converter with C-clamp.
(8) Position transmission on jack and secure it
with chains.
(9) Check condition of converter driveplate.
Replace the plate if cracked, distorted or damaged.
Also be sure transmission dowel pins are seated
in engine block and protrude far enough to
hold transmission in alignment.
(10) Raise transmission and align converter with
drive plate and converter housing with engine block.
(11) Move transmission forward. Then raise, lower
or tilt transmission to align converter housing with
engine block dowels.
(12) Carefully work transmission forward and over
engine block dowels until converter hub is seated in
crankshaft.
Fig. 62 Transmission Range Sensor Operation
1 - NEUTRAL CONTACT
2 - MANUAL LEVER AND SENSOR PLUNGER IN REVERSE
POSITION
3 - PARK CONTACT
4 - TRANSMISSION RANGE SENSOR
Fig. 63 Checking Converter Seating - Typical
1 - SCALE
2 - STRAIGHTEDGE
21 - 174 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

BRAKE TRANSMISSION SHIFT
INTERLOCK SYSTEM
DESCRIPTION
The Brake Transmission Shifter Interlock (BTSI)
(Fig. 74), is a solenoid operated system. It consists of
a solenoid permanently mounted on the gearshift
cable.
OPERATION
The system locks the shifter into the PARK posi-
tion. The interlock system is engaged whenever the
ignition switch is in the LOCK or ACCESSORY posi-
tion. An additional electrically activated feature will
prevent shifting out of the PARK position unless the
brake pedal is depressed approximately one-half an
inch. A magnetic holding device in line with the park
lock cable is energized when the ignition is in the
RUN position. When the key is in the RUN position
and the brake pedal is depressed, the shifter is
unlocked and will move into any position. The inter-
lock system also prevents the ignition switch from
being turned to the LOCK or ACCESSORY position,
unless the shifter is fully locked into the PARK posi-
tion.
DIAGNOSIS AND TESTING - BRAKE
TRANSMISSION SHIFT INTERLOCK
(1) Verify that the key can only be removed in the
PARK position
(2) When the shift lever is in PARK And the shift
handle pushbutton is in the ªOUTº position, the igni-
tion key cylinder should rotate freely from OFF toLOCK. When the shifter is in any other gear or neu-
tral position, the ignition key cylinder should not
rotate to the LOCK position.
(3) Shifting out of PARK should not be possible
when the ignition key cylinder is in the OFF posi-
tion.
(4) Shifting out of PARK should not be possible
while applying normal pushbutton force and ignition
key cylinder is in the RUN or START positions
unless the foot brake pedal is depressed approxi-
mately 1/2 inch (12mm).
(5) Shifting out of PARK should not be possible
when the ignition key cylinder is in the ACCESSORY
or LOCK positions.
(6) Shifting between any gears, NEUTRAL or into
PARK may be done without depressing foot brake
pedal with ignition switch in RUN or START posi-
tions.
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK
Correct cable adjustment is important to proper
interlock operation. The gearshift cable must be cor-
rectly adjusted in order to shift out of PARK.
ADJUSTMENT PROCEDURE
(1) Remove the steering column trim as necessary
for access to the brake transmission shift interlock.
(2) Shift the transmission into the PARK position.
(3) Pull upward on both the BTSI lock tab and the
gearshift cable lock tab (Fig. 75).
(4) Verify that the shift lever is in the PARK posi-
tion.
(5) Verify positive engagement of the transmission
park lock by attempting to rotate the propeller shaft.
The shaft will not rotate when the park lock is
engaged.
(6) Turn ignition switch to LOCK position.Be
sure ignition key cylinder is in the LOCK posi-
tion. Cable will not adjust correctly in any
other position.
(7) Ensure that the cable is free to self-adjust by
pushing cable rearward and releasing.
(8) Push the gearshift cable lock tab down until it
snaps in place.
(9) Locate the BTSI alignment hole in the bottom
of the BTSI mechanism between the BTSI lock tab
and the BTSI connector.
(10) Move the BTSI assembly up or down on the
gearshift cable until an appropriate size drill bit can
be inserted into the alignment hole and through the
assembly.
(11) Push the BTSI lock tab down until it snaps
into place and remove the drill bit.
(12) Install any steering column trim previously
removed.
Fig. 74 Brake Transmission Interlock Mechanism
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
21 - 196 AUTOMATIC TRANSMISSION - 48REDR

BTSI FUNCTION CHECK
(1) Verify removal of ignition key allowed in PARK
position only.
(2) When the shift lever is in PARK, the ignition
key cylinder should rotate freely from off to lock.
When the shifter is in any other position, the ignition
key should not rotate from off to lock.
(3) Shifting out of PARK should be possible when
the ignition key cylinder is in the off position.
(4) Shifting out of PARK should not be possible
while applying normal force, and ignition key cylin-
der is in the run or start positions, unless the foot
brake pedal is depressed approximately 1/2 inch
(12mm).
(5) Shifting out of PARK should not be possible
when the ignition key cylinder is in the accessory or
lock position.
(6) Shifting between any gear and NEUTRAL, or
PARK, may be done without depressing foot brake
with ignition switch in run or start positions.
(7) Engine starts must be possible with shifter
lever in PARK or NEUTRAL positions only. Engine
starts must not be possible in any position other than
PARK or NEUTRAL.
(8) With shifter lever in the:
²PARK position - Apply upward force on the shift
arm and remove pressure. Engine starts must be
possible.²PARK position - Apply downward force on the
shift arm and remove pressure. Engine starts must
be possible.
²NEUTRAL position - Normal position. Engine
starts must be possible.
²NEUTRAL position - Engine running and brakes
applied, apply upward force on the shift arm. Trans-
mission shall not be able to shift from neutral to
reverse.
ELECTRONIC GOVERNOR
DESCRIPTION
Governor pressure is controlled electronically. Com-
ponents used for governor pressure control include:
²Governor body
²Valve body transfer plate
²Governor pressure solenoid valve
²Governor pressure sensor
²Fluid temperature thermistor
²Throttle position sensor (TPS)
²Transmission speed sensor
²Powertrain control module (PCM)
GOVERNOR PRESSURE SOLENOID VALVE
The solenoid valve is a duty-cycle solenoid which
regulates the governor pressure needed for upshifts
and downshifts. It is an electro-hydraulic device
located in the governor body on the valve body trans-
fer plate (Fig. 76).
Fig. 75 Brake Transmission Interlock Mechanism
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
Fig. 76 Governor Pressure Solenoid Valve
1 - SOLENOID FILTER
2 - GOVERNOR PRESSURE SOLENOID
DRAUTOMATIC TRANSMISSION - 48RE 21 - 197
BRAKE TRANSMISSION SHIFT INTERLOCK SYSTEM (Continued)

GOVERNOR PRESSURE SENSOR
The governor pressure sensor measures output
pressure of the governor pressure solenoid valve (Fig.
77).
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate is designed to supply transmis-
sion line pressure to the governor pressure solenoid
valve and to return governor pressure.
The governor pressure solenoid valve is mounted in
the governor body. The body is bolted to the lower
side of the transfer plate (Fig. 77).
GOVERNOR PRESSURE CURVES
There are four governor pressure curves pro-
grammed into the transmission control module. The
different curves allow the control module to adjust
governor pressure for varying conditions. One curve
is used for operation when fluid temperature is at, or
below, ±1ÉC (30ÉF). A second curve is used when fluid
temperature is at, or above, 10ÉC (50ÉF) during nor-
mal city or highway driving. A third curve is used
during wide-open throttle operation. The fourth curve
is used when driving with the transfer case in low
range.
OPERATION
Compensation is required for performance varia-
tions of two of the input devices. Though the slope of
the transfer functions is tightly controlled, offset may
vary due to various environmental factors or manu-
facturing tolerances.
The pressure transducer is affected by barometric
pressure as well as temperature. Calibration of the
zero pressure offset is required to compensate for
shifting output due to these factors.
Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absenceof sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the9cold9period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higher
than normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
Fig. 77 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
21 - 198 AUTOMATIC TRANSMISSION - 48REDR
ELECTRONIC GOVERNOR (Continued)

sure curve is higher than normal to make the
transmission shift at normal speeds and sooner. The
PCM uses a temperature sensor in the transmission
oil sump to determine when low temperature gover-
nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous
stand-alone electronic module. This facilitated the
development of a load adaptive shift strategy - the
ability to alter the shift schedule in response to vehi-
cle load condition. One manifestation of this capabil-
ity is grade9hunting9prevention - the ability of the
transmission logic to delay an upshift on a grade if
the engine does not have sufficient power to main-
tain speed in the higher gear. The 3-2 downshift and
the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem-
ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low
range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine9flare.9The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.REMOVAL
(1) Hoist and support vehicle on safety stands.
(2) Remove transmission fluid pan and filter.
(3) Disengage wire connectors from pressure sen-
sor and solenoid (Fig. 78).
(4) Remove screws holding pressure solenoid
retainer to governor body.
(5) Separate solenoid retainer from governor (Fig.
79).
Fig. 78 Governor Solenoid And Pressure Sensor
1 - PRESSURE SENSOR
2 - PRESSURE SOLENOID
3 - GOVERNOR
Fig. 79 Pressure Solenoid Retainer
1 - PRESSURE SOLENOID RETAINER
2 - GOVERNOR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 199
ELECTRONIC GOVERNOR (Continued)

(2) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²overheat that generates sludge (fluid break-
down)
²failure to replace contaminated converter after
repair
The use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease and
other foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The torque converter should also be replaced when-
ever a failure generates sludge and debris. This is
necessary because normal converter flushing proce-
dures will not remove all contaminants.
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, thegeartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can
interfere with normal valve, clutch, and accumulator
operation. Foaming can also result in fluid escaping
from the transmission vent where it may be mis-
taken for a leak.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
Fluid level is checked with the engine running at
curb idle speed, the transmission in NEUTRAL and
the transmission fluid at normal operating tempera-
ture.The engine should be running at idle
speed for at least one minute, with the vehicle
on level ground.
The transmission fluid level can be checked two
ways.
PROCEDURE ONE
(1) Transmission fluid must be at normal operat-
ing temperature for accurate fluid level check. Drive
vehicle if necessary to bring fluid temperature up to
normal hot operating temperature of 82ÉC (180ÉF).
(2) Position vehicle on level surface.
(3) Start and run engine at curb idle speed.
(4) Apply parking brakes.
(5) Shift transmission momentarily into all gear
ranges. Then shift transmission back to NEUTRAL.
(6) Clean top of filler tube and dipstick to keep
dirt from entering tube.
(7) Remove dipstick (Fig. 87) and check fluid level
as follows:
(a) Correct acceptable level is in crosshatch area.
(b) Correct maximum level is to MAX arrow
mark.
(c) Incorrect level is at or below MIN line.
(d) If fluid is low, add only enough MopartAT F
+4 to restore correct level. Do not overfill.
Fig. 87 Dipstick Fluid Level Marks - Typical
1 - DIPSTICK
2 - MAXIMUM CORRECT FLUID LEVEL
3 - ACCEPTABLE FLUID LEVEL
21 - 202 AUTOMATIC TRANSMISSION - 48REDR
FLUID AND FILTER (Continued)