1998 DODGE RAM 1500 gear

PRESSURE TEST
Overdrive clutch Fourth gear only Pressure should be 524-565 kPa (76-82 psi) with
closed throttle and increase to 965 kPa (140 psi) at 1/2
to 3/4 throttle.
Line pressure (at
accumulator)Closed throttle 372-414 kPa (54-60 psi).
Front servo Third or Fourth gear only No more than 21 kPa (3 psi) lower than line pressure.
Rear servo 1 range No more than 21 kPa (3 psi) lower than line pressure.
R range 1103 kPa (160 psi) at idle, builds to 1862 kPa (270 psi)
at 1600 rpm.
Governor D range closed throttle Pressure should respond smoothly to changes in mph
and return to 0-7 kPa (0-1.5 psi) when stopped with
transmission in D, 1, 2. Pressure above 7 kPa (1.5 psi)
at stand still will prevent transmission from
downshifting.
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Fitting, cooler line at trans 18 13 -
Bolt, torque convertor 47 35 -
Bolt, clevis bracket to crossmember 47 35 -
Bolt, clevis bracket to rear support 68 50 -
Bolt, driveplate to crankshaft 75 55 -
Plug, front band reaction 17 13 -
Locknut, front band adj. 34 25 -
Bolt, fluid pan 13.6 - 120
Screws, fluid filter 4 - 35
Bolt, oil pump 20 15 -
Bolt, overrunning clutch cam 17 13 -
Bolt, O/D to trans. 34 25 -
Bolt, O/D piston retainer 17 13 -
Plug, pressure test port 14 10 -
Bolt, reaction shaft support 20 15 -
Locknut, rear band 41 30 -
Bolt, valve body to case 12 - 100
Sensor, trans speed 27 20 -
Screw, solenoid wiring connector 4 - 35
Screw, solenoid to transfer plate 4 - 35
Bracket, transmission range sensor mounting 34 25 -
Screw, transmision range sensor to mounting
bracket5-45
21 - 190 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

ACCUMULATOR
DESCRIPTION
The accumulator (Fig. 66) is a hydraulic device
that has the sole purpose of cushioning the applica-
tion of a band or clutch. The accumulator consists of
a dual-land piston and a spring located in a bore in
the transmission case. The 3-4 accumulator is located
in a housing attached to the side of the valve body
(Fig. 67).
OPERATION
Both the accumulator and the 3-4 accumulator
function the same. Line pressure is directed to the
small end of the piston when the transmission is
placed into a DRIVE position (Fig. 68), bottoming it
against the accumulator plate. When the 1-2 upshift
occurs (Fig. 69), line pressure is directed to the large
end of the piston and then to the kickdown servo. As
the line pressure reaches the accumulator, the com-
bination of spring pressure and line pressure forces
the piston away from the accumulator plate. This
causes a balanced pressure situation, which results
in a cushioned band application. After the kickdown
servo has become immovable, line pressure will fin-
ish pushing the accumulator up into its bore. When
the large end of the accumulator piston is seated in
its bore, the band or clutch is fully applied.
NOTE: The accumulator is shown in the inverted
position for illustrative purposes.
Fig. 66 Accumulator
1 - ACCUMULATOR PISTON
2 - PISTON SPRING
Fig. 67 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. 68 Accumulator in DRIVE - FIRST Gear Position
1 - LINE PRESSURE
DRAUTOMATIC TRANSMISSION - 48RE 21 - 193

INSPECTION
Inspect the accumulator piston and seal rings.
Replace the seal rings if worn or cut. Replace the pis-
ton if chipped or cracked.
Check condition of the accumulator inner and
outer springs. Replace the springs if the coils are
cracked, distorted or collapsed.
BANDS
DESCRIPTION
KICKDOWN (FRONT) BAND
The kickdown, or ªfrontº, band (Fig. 70) holds the
common sun gear of the planetary gear sets. The
front (kickdown) band is made of steel, and faced on
its inner circumference with a friction-type lining.
One end of the band is anchored to the transmission
case, and the other is acted on with a pushing force
by a servo piston. The front band is a single-wrap
design (the band does not completely encompass/
wrap the drum that it holds).
LOW/REVERSE (REAR) BAND
The low/reverse band, or ªrearº, band (Fig. 71) is
similar in appearance and operation to the front
band. The rear band is slightly different in that it
does not use a link bar, but is acted directly on by
the apply lever. This is referred to as a double-wrapband design (the drum is completely encompassed/
wrapped by the band). The double-wrap band pro-
vides a greater holding power in comparison to the
single-wrap design.
OPERATION
KICKDOWN (FRONT) BAND
The kickdown band holds the common sun gear of
the planetary gear sets by applying and holding the
front clutch retainer, which is splined to the sun gear
driving shell, and in turn splined directly to the sun
gear. The application of the band by the servo is typ-
ically done by an apply lever and link bar.
Fig. 69 Accumulator in SECOND Gear Position
1 - BOTTOM OF BORE
2 - LINE PRESSURE
3 - SHUTTLE VALVE
Fig. 70 Front Band
1 - FRONT BAND
2 - TRANSMISSION HOUSING
Fig. 71 Rear Band
1 - ADJUSTING SCREW
2 - LOCKNUT
3 - LEVER
4 - REAR BAND
5 - REACTION PIN
6 - O-RINGS
7 - PIVOT PIN
21 - 194 AUTOMATIC TRANSMISSION - 48REDR
ACCUMULATOR (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)

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)

(10) Place solenoid retainer in position on governor
(Fig. 84).
(11) Install screws to hold pressure solenoid
retainer to governor body.
(12) Engage wire connectors into pressure sensor
and solenoid (Fig. 85).
(13) Install transmission fluid pan and (new) filter.
(14) Lower vehicle and road test to verify repair.
EXTENSION HOUSING SEAL
REMOVAL
(1) Raise vehicle.
(2) Mark propeller shaft and axle yoke for align-
ment reference.
(3) Disconnect and remove propeller shaft.(4) Remove old seal with a screw mounted in a
slide hammer.
INSTALLATION
(1) Place seal in position on overdrive housing.
(2) Drive seal into overdrive housing with Seal
Installer 9037 (Fig. 86).
(3) Carefully guide propeller shaft slip yoke into
housing and onto output shaft splines. Align marks
made at removal and connect propeller shaft to rear
axle pinion yoke.
FLUID AND FILTER
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air
along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve and clutch operation. Foaming also causes fluid
expansion which can result in fluid overflow from the
transmission vent or fill tube. Fluid overflow can eas-
ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has two primary causes.
(1) A result of restricted fluid flow through the
main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.
Fig. 84 Pressure Solenoid Retainer
1 - PRESSURE SOLENOID RETAINER
2 - GOVERNOR
Fig. 85 Governor Solenoid And Pressure Sensor
1 - PRESSURE SENSOR
2 - PRESSURE SOLENOID
3 - GOVERNOR
Fig. 86 Installing Overdrive Housing Yoke Seal
1 - SPECIAL TOOL 9037
2 - SPECIAL TOOL C-4171
DRAUTOMATIC TRANSMISSION - 48RE 21 - 201
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)