1998 DODGE RAM 1500 tow

OPERATION
At key-on, overdrive operation is allowed. Pressing
the switch once causes the tow/haul overdrive OFF
mode to be entered and the Tow/Haul lamp to be illu-
minated. Pressing the switch a second time causes
normal overdrive operation to be restored and the
tow/haul lamp to be turned off. The tow/haul over-
drive OFF mode defaults to ON after the ignition
switch is cycled OFF and ON. The normal position
for the control switch is the ON position. The switch
must be in this position to energize the solenoid and
allow a 3-4 upshift. The control switch indicator light
illuminates only when the tow/haul overdrive switch
is turned to the OFF position, or when illuminated
by the transmission control module.
DIAGNOSIS AND TESTING - OVERDRIVE
ELECTRICAL CONTROLS
The tow/haul overdrive off switch, valve body sole-
noid, case connectors and related wiring can all be
tested with a 12 volt test lamp or a volt/ohmmeter.
Check continuity of each component when diagnosis
indicates this is necessary.
Switch and solenoid continuity should be checked
whenever the transmission fails to shift into fourth
gear range.
REMOVAL
(1) Using a plastic trim tool, remove the tow/haul
overdrive off switch retainer from the shift lever (Fig.
237).(2) Pull the switch outwards to release it from the
connector in the lever (Fig. 238)
INSTALLATION
NOTE: There is enough slack in the wire to pull out
the connector from the lever.
(1) Pull the connector out of the lever just enough
to grasp it.
CAUTION: Be careful not to bend the pins on the
tow/haul overdrive off switch. Use care when
installing the switch, as it is not indexed, and can
be accidentally installed incorrectly.
(2) Install the tow/haul overdrive off switch into
the connector (Fig. 239)
(3) Push the tow/haul overdrive off switch and wir-
ing into the shift lever.
(4) Install the tow/haul overdrive off switch
retainer onto the shift lever.
Fig. 237 Tow/Haul Overdrive Off Switch Retainer
Fig. 238 Remove the Tow/Haul Overdrive Off Switch
Fig. 239 Install the Tow/Haul Overdrive Off Switch
21 - 262 AUTOMATIC TRANSMISSION - 48REDR
TOW/HAUL OVERDRIVE SWITCH (Continued)

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

KICKDOWN LIMIT VALVE
The purpose of the limit valve is to prevent a 3-2
downshift at higher speeds when a part-throttle
downshift is not desirable. At these higher speeds
only a full throttle 3-2 downshift will occur. At low
road speeds (Fig. 258) the limit valve does not come
into play and does not affect the downshifts. As the
vehicle's speed increases (Fig. 259), the governor
pressure also increases. The increased governor pres-
sure acts on the reaction area of the bottom land of
the limit valve overcoming the spring force trying topush the valve toward the bottom of its bore. This
pushes the valve upward against the spring and bot-
toms the valve against the top of the housing. With
the valve bottomed against the housing, the throttle
pressure supplied to the valve will be closed off by
the bottom land of the limit valve. When the supply
of throttle pressure has been shut off, the 3-2 part
throttle downshift plug becomes inoperative, because
no pressure is acting on its reaction area.
Fig. 258 Kickdown Limit Valve - Low Speeds
Fig. 259 Kickdown Limit Valve - High Speeds
DRAUTOMATIC TRANSMISSION - 48RE 21 - 277
VALVE BODY (Continued)

3-4 TIMING VALVE
The 3-4 timing valve is moved by line pressure
coming through the 3-4 shift valve (Fig. 266) or the
converter clutch valve. After the shift, the timing
valve holds the 2-3 shift valve in an upshift position.
The purpose is to prevent the 2-3 valve from down-
shifting while either the overdrive clutch or converter
clutch is applied (Fig. 265).
3-4 QUICK FILL VALVE
The 3-4 quick fill valve provides faster engagement
of the overdrive clutch during 3-4 upshifts. The valve
temporarily bypasses the clutch piston feed orifice at
the start of a 3-4 upshift (Fig. 265). This exposes a
larger passage into the piston retainer resulting in a
much faster clutch fill and apply sequence. The quick
fill valve does not bypass the regular clutch feed ori-
fice throughout the 3-4 upshift. Instead, once a pre-
determined pressure develops within the clutch, the
valve closes the bypass (Fig. 266). Clutch fill is then
completed through the regular feed orifice.
THROTTLE VALVE
In all gear positions the throttle valve (Fig. 267) is
being supplied with line pressure. The throttle valve
meters and reduces the line pressure that now
becomes throttle pressure. The throttle valve is
moved by a spring and the kickdown valve, which is
mechanically connected to the throttle. The larger
the throttle opening, the higher the throttle pressure
(to a maximum of line pressure). The smaller the
throttle opening, the lower the throttle pressure (to a
minimum of zero at idle). As engine speed increases,the increase in pump speed increases pump output.
The increase in pressure and volume must be regu-
lated to maintain the balance within the transmis-
sion. To do this, throttle pressure is routed to the
reaction area on the right side of the throttle pres-
sure plug (in the regulator valve).
The higher engine speed and line pressure would
open the vent too far and reduce line pressure too
much. Throttle pressure, which increases with engine
speed (throttle opening), is used to oppose the move-
ment of the pressure valve to help control the meter-
ing passage at the vent. The throttle pressure is
combined with spring pressure to reduce the force of
the throttle pressure plug on the pressure valve. The
larger spring at the right closes the regulator valve
passage and maintains or increases line pressure.
The increased line pressure works against the reac-
tion area of the line pressure plug and the reaction
area left of land #3 simultaneously moves the regu-
lator valve train to the right and controls the meter-
ing passage.
The kickdown valve, along with the throttle valve,
serve to delay upshifts until the correct vehicle speed
has been reached. It also controls downshifts upon
driver demand, or increased engine load. If these
valves were not in place, the shift points would be at
the same speed for all throttle positions. The kick-
down valve is actuated by a cam connected to the
throttle. This is accomplished through either a link-
age or a cable. The cam forces the kickdown valve
toward the throttle valve compressing the spring
between them and moving the throttle valve. As the
throttle valve land starts to uncover its port, line
Fig. 267 Throttle Valve
21 - 282 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

3-4 ACCUMULATOR HOUSING
(1) Remove end plate from housing.
(2) Remove piston spring.
(3) Remove piston. Remove and discard piston
seals (Fig. 304).
CLEANING
Clean the valve housings, valves, plugs, springs,
and separator plates with a standard parts cleaning
solution only. Do not use gasoline, kerosene, or any
type of caustic solution.
Do not immerse any of the electrical components in
cleaning solution. Clean the governor solenoid and
sensor and the dual solenoid and harness assembly
by wiping them off with dry shop towels only.
Dry all except the electrical parts with compressed
air. Make sure all passages are clean and free from
obstructions.Do not use rags or shop towels to
dry or wipe off valve body components. Lint
from these materials can stick to valve body
parts, interfere with valve operation, and clog
filters and fluid passages.
Wipe the governor pressure sensor and solenoid
valve with dry, lint free shop towels only. The O-rings
on the sensor and solenoid valve are the only service-
able components. Be sure the vent ports in the sole-
noid valve are open and not blocked by dirt or debris.
Replace the valve and/or sensor only when DRB scan
tool diagnosis indicates this is necessary. Or, if eitherpart has sustained physical damage (dented,
deformed, broken, etc.).
CAUTION: Do not turn the small screw at the end of
the solenoid valve for any reason. Turning the
screw in either direction will ruin solenoid calibra-
tion and result in solenoid failure. In addition, the
filter on the solenoid valve is NOT serviceable. Do
not try to remove the filter as this will damage the
valve housing.
INSPECTION
Inspect the throttle and manual valve levers and
shafts. Do not attempt to straighten a bent shaft or
correct a loose lever. Replace these components if
worn, bent, loose or damaged in any way.
Inspect all of the valve body mating surfaces for
scratches, nicks, burrs, or distortion. Use a straight-
edge to check surface flatness. Minor scratches may
be removed with crocus cloth using only very light
pressure.
Minor distortion of a valve body mating surface
may be corrected by smoothing the surface with a
sheet of crocus cloth. Position the crocus cloth on a
surface plate, sheet of plate glass or equally flat sur-
face. If distortion is severe or any surfaces are
heavily scored, the valve body will have to be
replaced.
CAUTION: Many of the valves and plugs, such as
the throttle valve, shuttle valve plug, 1-2 shift valve
and 1-2 governor plug, are made of coated alumi-
num. Aluminum components are identified by the
dark color of the special coating applied to the sur-
face (or by testing with a magnet). Do not sand alu-
minum valves or plugs under any circumstances.
This practice could damage the special coating
causing the valves/plugs to stick and bind.
Inspect the valves and plugs for scratches, burrs,
nicks, or scores. Minor surface scratches on steel
valves and plugs can be removed with crocus cloth
butdo not round off the edges of the valve or
plug lands.Maintaining sharpness of these edges is
vitally important. The edges prevent foreign matter
from lodging between the valves and plugs and the
bore.
Inspect all the valve and plug bores in the valve
body. Use a penlight to view the bore interiors.
Replace the valve body if any bores are distorted or
scored. Inspect all of the valve body springs. The
springs must be free of distortion, warpage or broken
coils.
Fig. 304 3-4 Accumulator and Housing
1 - ACCUMULATOR PISTON
2 - 3-4 ACCUMULATOR HOUSING
3 - TEFLON SEALS
4 - PISTON SPRING
5 - COVER PLATE AND SCREWS
21 - 298 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

INSTALLATION........................391
OUTPUT SPEED SENSOR
DESCRIPTION........................391
OPERATION..........................391
REMOVAL............................391
INSTALLATION........................392
TOW/HAUL OVERDRIVE SWITCH
DESCRIPTION........................392
OPERATION..........................392
REMOVAL............................392
INSTALLATION........................393
PISTONS
DESCRIPTION........................393
OPERATION..........................393
PLANETARY GEARTRAIN
DESCRIPTION........................395
OPERATION..........................396
DISASSEMBLY........................396
CLEANING...........................396
INSPECTION.........................397
ASSEMBLY...........................397
SHIFT MECHANISM
DESCRIPTION........................398
OPERATION..........................398
SOLENOID SWITCH VALVE
DESCRIPTION........................398
OPERATION..........................398
SOLENOIDS
DESCRIPTION........................398OPERATION..........................399
TORQUE CONVERTER
DESCRIPTION........................399
OPERATION..........................403
REMOVAL............................404
INSTALLATION........................404
TRANSMISSION CONTROL RELAY
DESCRIPTION........................405
OPERATION..........................405
TRANSMISSION RANGE SENSOR
DESCRIPTION........................405
OPERATION..........................405
TRANSMISSION SOLENOID/TRS ASSEMBLY
DESCRIPTION........................406
OPERATION..........................406
REMOVAL............................407
INSTALLATION........................408
TRANSMISSION TEMPERATURE SENSOR
DESCRIPTION........................408
OPERATION..........................408
VALVE BODY
DESCRIPTION........................408
OPERATION..........................408
REMOVAL............................410
DISASSEMBLY........................410
CLEANING...........................412
INSPECTION.........................413
ASSEMBLY...........................414
INSTALLATION........................414
AUTOMATIC TRANSMISSION -
45RFE/545RFE
DESCRIPTION
The 45RFE/545RFE automatic transmissions is a
sophisticated, multi-range, electronically controlled
transmission which combines optimized gear ratios
for responsive performance, state of the art efficiency
features and low NVH. Other features include driver
adaptive shifting and three planetary gear sets to
provide wide ratio capability with precise ratio steps
for optimum driveability. The three planetary gear
sets also make available a unique alternate second
gear ratio. The primary 2nd gear ratio fits between
1st and 3rd gears for normal through-gear accelera-
tions. The alternate second gear ratio (2prime) allows
smoother 4-2 kickdowns at high speeds to provide
2nd gear passing performance over a wider highway
cruising range.
The hydraulic portion of the transmission consists
of the transmission fluid, fluid passages, hydraulic
valves, and various line pressure control components.The primary mechanical components of the trans-
mission consist of the following:
²Three multiple disc input clutches
²Three multiple disc holding clutches
²Five hydraulic accumulators
²Three planetary gear sets
²Dual Stage Hydraulic oil pump
²Valve body
²Solenoid pack
The TCM is the ªheartº or ªbrainº of the electronic
control system and relies on information from vari-
ous direct and indirect inputs (sensors, switches, etc.)
to determine driver demand and vehicle operating
conditions. With this information, the TCM can cal-
culate and perform timely and quality shifts through
various output or control devices (solenoid pack,
transmission control relay, etc.).
21 - 312 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR

(43) Remove the park pawl rod and e-clip (Fig. 31).
(44) Remove the park pawl rod guide snap-ring
(Fig. 31).
(45) Remove the park pawl rod guide (Fig. 31).
(46) Remove the park pawl pivot shaft, park pawl,
and spring (Fig. 31).
(47) Remove the manual selector shaft (Fig. 31).
(48) Remove the manual selector shaft seal.
(49) Remove the dipstick tube seal.
CLEANING
The use of crocus cloth is permissible where neces-
sary, providing it is used carefully. When used on shafts,
or valves, use extreme care to avoid rounding off sharp
edges. Sharp edges are vital as they prevent foreign
matter from getting between the valve and valve bore.
Do not reuse oil seals, gaskets, seal rings, or O-rings
during overhaul. Replace these parts as a matter of
course. Also do not reuse snap rings or E-clips that are
bent or distorted. Replace these parts as well.
Lubricate transmission parts with MopartATF +4,
Automatic Transmission Fluid, during overhaul and
assembly. Use petroleum jelly, MopartDoor Ease, or
Ru-Glyde to prelubricate seals, O-rings, and thrust
washers. Petroleum jelly can also be used to hold
parts in place during reassembly.Clean the case in a solvent tank. Flush the case
bores and fluid passages thoroughly with solvent.
Dry the case and all fluid passages with compressed
air. Be sure all solvent is removed from the case and
that all fluid passages are clear.
NOTE: Do not use shop towels or rags to dry the
case (or any other transmission component) unless
they are made from lint-free materials. Lint will stick
to case surfaces and transmission components and
circulate throughout the transmission after assem-
bly. A sufficient quantity of lint can block fluid pas-
sages and interfere with valve body operation.
INSPECTION
Inspect the case for cracks, porous spots, worn
bores, or damaged threads. Damaged threads can be
repaired with Helicoil thread inserts. However, the
case will have to be replaced if it exhibits any type of
damage or wear.
ASSEMBLY
(1) Clean and inspect all components. Replace any
components which show evidence of excessive wear
or scoring.
(2) Install the cooler filter bypass valve.
(3) Torque the bypass valve to specification. The
valve uses a tapered pipe thread and excessive
torque can damage the transmission case. Tighten
the cooler filter bypass valve to 4.5 N´m (40 in.lbs.).
(4) Install a new selector shaft seal using Seal
Installer 8253 (Fig. 32).
Fig. 31 Manual Shaft/Park Lock Components
1 - GUIDE
2 - SNAP-RING
3 - SHAFT
4 - SPRING
5 - PARK PAWL
6 - MANUAL SHAFT/LEVER
7 - PARK ROD
Fig. 32 Install Selector Shaft
1 - SEAL
2 - TOOL 8253
21 - 326 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
AUTOMATIC TRANSMISSION - 45RFE/545RFE (Continued)

(5) Install the manual selector shaft and retaining
screw. Tighten the manual selector shaft retaining
screw to 28 N´m (250 in.lbs.).
(6) Install the park pawl, spring, and shaft (Fig.
33).
(7) Install the park rod and e-clip (Fig. 33).
(8) Install the park rod guide and snap-ring (Fig.
33).
(9) Install a new dipstick tube seal using Seal
Installer 8254 (Fig. 34).
NOTE: Before final assembly of transmission cen-
terline, the 2C/4C clutch components should be
installed into position and measured as follows:
(10) Install the 2C reaction plate into the trans-
mission case (Fig. 35).
(11) Install the 2C clutch pack into the transmis-
sion case (Fig. 35).
(12) Install the flat 2C clutch snap-ring into the
transmission case (Fig. 35).
(13) Install the 4C retainer/bulkhead into the
transmission case. Make sure that the oil feed holes
are pointing toward the valve body area.(14) Install the 4C retainer/bulkhead tapered
snap-ring into the transmission case. Make sure that
the open ends of the snap-ring are located in the case
opening toward the valve body area.
(15) Using a feeler gauge through the opening in
the rear of the transmission case, measure the 2C
clutch pack clearance between the 2C reaction plate
and the transmission case at four different points.
The average of these measurements is the 2C clutch
pack clearance. The correct clutch clearance is 0.455-
1.335 mm (0.018-0.053 in.). The reaction plate is not
selective. If the clutch pack clearance is not within
Fig. 33 Manual Shaft/Park Lock Components
1 - GUIDE
2 - SNAP-RING
3 - SHAFT
4 - SPRING
5 - PARK PAWL
6 - MANUAL SHAFT/LEVER
7 - PARK ROD
Fig. 34 Install Dipstick Tube Seal Using Tool 8254
1 - TOOL 8254
2 - SEAL
Fig. 35 Install 2C Clutch Pack
1 - SNAP-RING
2 - PLATE
3 - DISC
4 - REACTION PLATE
DRAUTOMATIC TRANSMISSION - 45RFE/545RFE 21 - 327
AUTOMATIC TRANSMISSION - 45RFE/545RFE (Continued)