Valve body DODGE RAM 1500 1998 2.G Owner's Guide

(15) Install air duct to air box.
(16) Connect battery cable to battery.
(17) Start engine and check for leaks.
5.7L V-8
(1) If fuel injectors are to be installed, refer to Fuel
Injector Removal/Installation.
(2) Clean out fuel injector machined bores in
intake manifold.
(3) Apply a small amount of engine oil to each fuel
injector o-ring. This will help in fuel rail installation.
(4) Position fuel rail/fuel injector assembly to
machined injector openings in intake manifold.
(5) Guide each injector into intake manifold. Be
careful not to tear injector o-rings.
(6) Pushrightside of fuel rail down until fuel
injectors have bottomed on shoulders. Pushleftfuel
rail down until injectors have bottomed on shoulders.
(7) Install 4 fuel rail holdown clamps and 4 mount-
ing bolts. Refer to Torque Specifications.
(8) Position spark plug cable tray and cable assem-
bly to intake manifold. Snap 4 cable tray retaining
clips into intake manifold.
(9) Install all cables to spark plugs and ignition
coils.
(10) Connect electrical connector to throttle body.
(11) Install electrical connectors to all 8 ignition
coils. Refer to Ignition Coil Removal/Installation.
(12) Connect electrical connector to throttle body.
(13) Connect electrical connectors at all fuel injec-
tors. To install connector, refer to (Fig. 17). Push con-
nector onto injector (1) and then push and lock red
colored slider (2). Verify connector is locked to injec-
tor by lightly tugging on connector.
(14) Connect fuel line latch clip and fuel line to
fuel rail. Refer to Quick-Connect Fittings.
(15) Install air resonator to throttle body (2 bolts).
(16) Install flexible air duct to air box.
(17) Connect battery cable to battery.
(18) Start engine and check for leaks.
FUEL TANK
DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for place-
ment of the fuel pump module, and (if equipped) cer-
tain ORVR components.
OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.Two check (control) valves are mounted into the
top of the fuel tank. Refer to Fuel Tank Check Valve
for additional information.
An evaporation control system is connected to the
fuel tank to reduce emissions of fuel vapors into the
atmosphere. When fuel evaporates from the fuel
tank, vapors pass through vent hoses or tubes to a
charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP) and/or an On-Board Refueling
Vapor Recovery (ORVR) system. Refer to Emission
Control System for additional information.
REMOVAL- EXCEPT DIESEL
Fuel Tank Draining
WARNING: THE FUEL SYSTEM MAY BE UNDER
CONSTANT FUEL PRESSURE EVEN WITH THE
ENGINE OFF. THIS PRESSURE MUST BE
RELEASED BEFORE SERVICING FUEL TANK.
Two different procedures may be used to drain fuel
tank: through the fuel fill fitting on tank, or using
the DRBtscan tool. Due to a one-way check valve
installed into the fuel fill opening fitting at the tank,
the tank cannot be drained conventionally at the fill
cap.
The quickest draining procedure involves removing
the rubber fuel fill hose.
As an alternative procedure, the electric fuel pump
may be activated allowing tank to be drained at fuel
rail connection. Refer to DRB scan tool for fuel pump
activation procedures. Before disconnecting fuel line
at fuel rail, release fuel pressure. Refer to the Fuel
System Pressure Release Procedure for procedures.
Attach end of special test hose tool number 6541,
6539, 6631 or 6923 at fuel rail disconnection (tool
number will depend on model and/or engine applica-
tion). Position opposite end of this hose tool to an
approved gasoline draining station. Activate fuel
pump and drain tank until empty.
If electric fuel pump is not operating, fuel must be
drained through fuel fill fitting at tank. Refer to fol-
lowing procedures.
(1) Release fuel system pressure.
(2) Raise vehicle.
(3) Thoroughly clean area around fuel fill fitting
and rubber fuel fill hose at tank.
(4) If vehicle is equipped with 4 doors and a 6 foot
(short) box, remove left-rear tire/wheel.
(5) Loosen clamp (Fig. 23) and disconnect rubber
fuel fill hose at tank fitting. Using an approved gas
holding tank, drain fuel tank through this fitting.
DRFUEL DELIVERY - GAS 14 - 17
FUEL RAIL (Continued)

INSTALLATION
Threads of new oxygen sensors are factory coated
with anti-seize compound to aid in removal.DO
NOT add any additional anti-seize compound to
threads of a new oxygen sensor.
(1) Install O2S sensor. Tighten to 30 N´m (22 ft.
lbs.) torque.
(2) Connect O2S sensor wire connector.
(3) Lower vehicle.
PTO SWITCH
DESCRIPTION
This Powertrain Control Module (PCM) input is
used only on models equipped with aftermarket
Power Take Off (PTO) units.
OPERATION
The input is used only to tell the PCM (or ECM-
Diesel) that the PTO has been engaged. The PCM (or
ECM) will disable (temporarily shut down) certain
OBD II diagnostic trouble codes when the PTO is
engaged.
JTEC and NGC Engine Controllers:When the
aftermarket PTO switch has been engaged, a 12V +
signal is sent through circuit G113 to PCM pin A13.
The PCM will then sense and determine that the
PTO has been activated.
CM 845 or CM 848 Diesel Engine Controllers:
When the aftermarket PTO switch has been engaged,
a 12V + signal is sent through circuit G113 to ECM
pin B38. The ECM will then sense and determine
that the PTO has been activated.
THROTTLE BODY
DESCRIPTION
The throttle body is located on the intake manifold.
Fuel does not enter the intake manifold through the
throttle body. Fuel is sprayed into the manifold by
the fuel injectors.
OPERATION
Filtered air from the air cleaner enters the intake
manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.
5.7L V-8 Engine:
The throttle body on the 5.7L engine is an electri-
cally controlled unit. A mechanical cable is not used
to connect the throttle body to the accelerator pedal.
The Accelerator Pedal Position Sensor (APPS) alongwith inputs from other sensors sets the throttle blade
to pre-determined positions.
Except 5.7L V-8 Engine:
Certain sensors are attached to the throttle body.
The accelerator pedal cable, speed control cable and
transmission control cable (when equipped) are con-
nected to the throttle body linkage arm.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
REMOVAL
3.7L V-6
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the Powertrain Control Module (PCM).
(1) Remove air cleaner tube at throttle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS.
(3) Remove all control cables from throttle body
(lever) arm. Refer to the Accelerator Pedal and Throt-
tle Cable section for removal/installation procedures.
(4) Disconnect necessary vacuum lines at throttle
body.
(5) Remove 3 throttle body mounting bolts (Fig.
28).
(6) Remove throttle body from intake manifold.
(7) Check condition of old throttle body-to-intake
manifold o-ring (Fig. 29).
4.7L V-8
(1) Remove air duct and air resonator box at throt-
tle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS (Fig. 30).
(3) Remove vacuum line at throttle body.
(4) Remove all control cables from throttle body
(lever) arm. Refer to Accelerator Pedal and Throttle
Cable.
(5) Remove three throttle body mounting bolts
(Fig. 30).
(6) Remove throttle body from intake manifold.
5.7L V-8
CAUTION: Do not use spray (carb) cleaners on any
part of the throttle body. Do not apply silicone lubri-
cants to any part of the throttle body.
(1) Remove air duct and air resonator box at throt-
tle body.
14 - 36 FUEL INJECTION - GASDR
OXYGEN SENSOR (Continued)

SPECIFICATIONS
FUEL INJECTOR FIRING ORDER - DIESEL
1±5±3±6±2±4
TORQUE - FUEL SYSTEM - DIESEL ENGINE
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Accelerator Pedal Bracket Mounting 12 - 105
Accelerator Pedal Position Sensor
Bracket-to-Battery Tray Bolts3-30
Crankshaft Position Sensor 9 80
Camshaft Position Sensor 9 - 80
Engine Coolant Temperature Sensor 18 15 160
Rear Engine Lift Bracket Bolts 77 56 -
Fuel Connector Nut at Cylinder Head 50 37 -
Fuel Filler Hose Clamp at Tank 3 - 30
Fuel Filler Housing-to-Body Screws 2 - 17
Fuel Filter Lid 34 25 -
Fuel Filter Drain Valve Screws 1.5 - 14
Fuel Heater Element Screws 1.5 - 14
Fuel Pump Module Lock Ring 54 40 -
Fuel Line Banjo Fitting Bolts 24 18 -
Fuel Line Fittings (High-Pressure - Pump
to Rail)37 27 -
Fuel Line Fittings (High-Pressure -
Cylinder head to Rail)30 22 -
Bracket Over #6 Fuel Line (Bolts) 43 32 -
Fuel Injector Solenoid Nuts 1.25 - 11
Fuel Injection Pump-to-Gear Shaft Nut 105 77 -
Fuel Injection Pump Mounting Nuts 24 18 -
Fuel Line Support Clamps (High-
Pressure)24 18 -
Fuel Pressure Sensor 70 52 -
Fuel Pressure Limiting Valve (Banjo Bolt) 24 17 -
Fuel Pressure Limiting Valve (In Fuel
Rail)70 52 -
Fuel Rail Mounting Bolts 24 18 200
Fuel Tank Mounting Straps 41 30 -
Map Sensor Mounting Screws 1 - 9
ECM-to-Engine Bracket Mounting Bolts 24 18 -
ECM Electrical Harness Connector 3 - 27
Water-In-Fuel Sensor 4.5 - 39
14 - 48 FUEL DELIVERY - DIESELDR
FUEL DELIVERY - DIESEL (Continued)

FUEL TANK
DESCRIPTION - DIESEL
The fuel tank is similar to the tank used with gas-
oline powered models. The tank is equipped with a
separate fuel return line and a different fuel tank
module for diesel powered models. A fuel tank
mounted, electric fuel pump is not used with diesel
powered models. Refer to Fuel Tank Module for addi-
tional information.
REMOVAL - DIESEL
Fuel Tank Draining
Due to a one-way check valve installed into the
fuel fill opening fitting at the tank, the tank cannot
be drained conventionally at the fill cap.
(1) Raise vehicle.
(2) If vehicle is equipped with 4 doors and a 6 foot
(short) box, remove left-rear tire/wheel.
(3) Thoroughly clean area at top of fuel tank
around fuel tank module.
(4) Remove rubber cap from auxiliary fitting on
top of tank module (Fig. 19).
(5) Drain fuel tank by attaching drain hose from
an approved draining station to auxiliary fitting on
top of tank module (Fig. 19).
Tank Removal
(1) Loosen clamp and disconnect rubber fuel fill
hose at tank.
(2) Support tank with a hydraulic jack.
(3) Remove 2 fuel tank strap nuts (Fig. 20) and
remove both tank support straps.
(4) Carefully lower tank a few inches and discon-
nect fuel pump module electrical connector (Fig. 19)
at top of tank. To disconnect electrical connector:
Push upward on red colored tab to unlock. Push on
black colored tab while removing connector.
(5) Disconnect fuel supply and return lines at fuel
tank module (Fig. 19). Refer to Quick-Connect Fit-
tings for procedures.
(6) Continue to lower tank for removal.
(7) If fuel tank is to be replaced, remove fuel tank
module from tank. Refer to Fuel Tank Module
Removal/Installation procedures.INSTALLATION - DIESEL
(1) If fuel tank is to be replaced, install fuel tank
module into tank. Refer to Fuel Tank Module Remov-
al/Installation procedures.
(2) Position fuel tank to hydraulic jack.
(3) Raise tank until positioned near body.
(4) Connect fuel tank module electrical connector
at top of tank.
(5) Connect fuel supply and return lines to tank
module.
(6) Continue raising tank until positioned snug to
body.
(7) Install and position both tank support straps.
Install 2 fuel tank strap nuts and tighten.Tighten
rear strap nut first.Refer to Torque Specifications.
(8) Remove hydraulic jack.
(9) Connect rubber fill hose to fuel fill tube and
tighten clamp.
(10) Install tire / wheel (if necessary).
(11) Lower vehicle.
(12) Fill fuel tank with fuel.
(13) Start engine and check for fuel leaks near top
of module.
Fig. 19 FUEL TANK MODULE - DIESEL
1 - TOP OF FUEL TANK
2 - AUX. FITTING
3 - ELEC. CONNECTOR
4 - FUEL TANK MODULE (TOP)
5 - LOCKNUT
6 - FUEL SUPPLY LINE
7 - FUEL RETURN LINE
14 - 62 FUEL DELIVERY - DIESELDR

(8) Fill the system with fluid and perform Steering
Pump Initial Operation, (Refer to 19 - STEERING/
PUMP - STANDARD PROCEDURE).
(9) Start the engine and run it for fifteen minutes
then stop the engine.
(10) Remove the return line/lines from the pump
and plug the pump port/ports.
(11) Pour fresh fluid into the reservoir and check
the draining fluid for contamination. If the fluid is
still contaminated, then flush the system again.
(12) Install the return line/lines and perform
Steering Pump Initial Operation, (Refer to 19 -
STEERING/PUMP - STANDARD PROCEDURE).
REMOVAL
REMOVAL - GAS
(1) Drain and siphon the power steering fluid from
the reservoir.
(2) Remove the serpentine belt.
CAUTION: Do not remove the fitting on the pump
that the high pressure hose screws into. The fitting
may come loose unless it is backed up using
another wrench. If the fitting does come loose, it
must be retightened before continuing. (57 - 67Nm,
40 - 50 lbft) If this fitting comes out of the pump
body, the internal spring and valve parts will fall out
of the pump and they cannot be reinstalled prop-
erly. If this occurs the pump needs to be replaced
with a new pump.
(3) Disconnect the return hose. (Fig. 2)
(4) Disconnect the pressure hose. (Fig. 2)
(5) Access to remove the three bolts securing the
pump to the cylinder head can be gained thru the
pulley holes. (Fig. 2)
REMOVAL - DIESEL
(1) Drain and siphon the power steering fluid from
the reservoir.
(2) Remove the serpentine belt.
CAUTION: Do not remove the fitting on the pump
that the high pressure hose screws into. The fitting
may come loose unless it is backed up using
another wrench. If the fitting does come loose, it
must be retightened before continuing. (57 - 67Nm,
40 - 50 lbft) If this fitting comes out of the pump
body, the internal spring and valve parts will fall out
of the pump and they cannot be reinstalled prop-
erly. If this occurs the pump needs to be replaced
with a new pump.
(3) Disconnect the return hose.
(4) Disconnect the pressure hose.(5) Access to remove the three bolts securing the
pump to the cylinder head can be gained thru the
pulley holes.
(6) Loosen the pump bracket to the block.
(7) Remove the 6 intake plenum bolts (Fig. 3).
(8) loosen the inner cooler tube clamp at the
intake plenum and remove the intake plenum.
(9) Loosen the inner cooler tube clamp at the radi-
ator support side and remove the tube from the vehi-
cle.
(10) Remove the power steering pump from the top
of the engine compartment where the intake plenum
was (Fig. 3).
Fig. 2 POWER STEERING PUMP
1 - POWER STEERING PULLEY
2 - POWER STEERING RESERVOIR
3 - RETURN HOSE
4 - HIGH PRESSURE HOSE
Fig. 3 POWER STEERING PUMP ACCESS
1 - INTAKE PLENUM MOUNTING
2 - POWER STEERING PUMP
DRPUMP 19 - 41
PUMP (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

AUTOMATIC TRANSMISSION -
48RE
DESCRIPTION
The 48RE (Fig. 1) is a four speed fully automatic
transmissions with an electronic governor. The 48RE
is equipped with a lock-up clutch in the torque con-
verter. First through third gear ranges are provided
by the clutches, bands, overrunning clutch, and plan-
etary gear sets in the transmission. Fourth gear
range is provided by the overdrive unit that contains
an overdrive clutch, direct clutch, planetary gear set,
and overrunning clutch.
The transmission contains a front, rear, and direct
clutch which function as the input driving compo-
nents. It also contains the kickdown (front) and thelow/reverse (rear) bands which, along with the over-
running clutch and overdrive clutch, serve as the
holding components. The driving and holding compo-
nents combine to select the necessary planetary gear
components, in the front, rear, or overdrive planetary
gear set, transfer the engine power from the input
shaft through to the output shaft.
The valve body is mounted to the lower side of the
transmission and contains the valves to control pres-
sure regulation, fluid flow control, and clutch/band
application. The oil pump is mounted at the front of
the transmission and is driven by the torque con-
verter hub. The pump supplies the oil pressure nec-
essary for clutch/band actuation and transmission
lubrication.
21 - 132 AUTOMATIC TRANSMISSION - 48REDR

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)

DIRECT DRIVE POWERFLOW
The vehicle has accelerated and reached the shift
point for the 2-3 upshift into direct drive (Fig. 8).
When the shift takes place, the front band is
released, and the front clutch is applied. The rear
clutch stays applied as it has been in all the forward
gears. With the front clutch now applied, engine
torque is now on the front clutch retainer, which is
locked to the sun gear driving shell. This means that
the sun gear is now turning in engine rotation (clock-
wise) and at engine speed. The rear clutch is still
applied so engine torque is also still on the front
annulus gear. If two members of the same planetary
set are driven, direct drive results. Therefore, when
two members are rotating at the same speed and in
the same direction, it is the same as being locked up.
The rear planetary set is also locked up, given the
sun gear is still the input, and the rear annulus gear
must turn with the output shaft. Both gears are
turning in the same direction and at the same speed.
The front and rear planet pinions do not turn at all
in direct drive. The only rotation is the input from
the engine to the connected parts, which are acting
as one common unit, to the output shaft.
FOURTH GEAR POWERFLOW
Fourth gear overdrive range is electronically con-
trolled and hydraulically activated. Various sensor
inputs are supplied to the powertrain control module
to operate the overdrive solenoid on the valve body.
The solenoid contains a check ball that opens and
closes a vent port in the 3-4 shift valve feed passage.
The overdrive solenoid (and check ball) are not ener-
gized in first, second, third, or reverse gear. The vent
port remains open, diverting line pressure from the
2-3 shift valve away from the 3-4 shift valve. The
Tow/Haul control switch must be in the ON position
to transmit overdrive status to the PCM. A 3-4
upshift occurs only when the overdrive solenoid is
energized by the PCM. The PCM energizes the over-
drive solenoid during the 3-4 upshift. This causes the
solenoid check ball to close the vent port allowing
line pressure from the 2-3 shift valve to act directly
on the 3-4 upshift valve. Line pressure on the 3-4
shift valve overcomes valve spring pressure moving
the valve to the upshift position. This action exposes
the feed passages to the 3-4 timing valve, 3-4 quick
fill valve, 3-4 accumulator, and ultimately to the
overdrive piston. Line pressure through the timing
Fig. 8 Direct Drive Powerflow
1 - FRONT CLUTCH APPLIED 6 - INPUT SHAFT
2 - OVER-RUNNING CLUTCH FREE-WHEELING 7 - OVER-RUNNING CLUTCH FREE-WHEELING
3 - OUTPUT SHAFT 8 - REAR CLUTCH APPLIED
4 - REAR CLUTCH APPLIED 9 - FRONT CLUTCH APPLIED
5 - OUTPUT SHAFT 10 - INPUT SHAFT
DRAUTOMATIC TRANSMISSION - 48RE 21 - 139
AUTOMATIC TRANSMISSION - 48RE (Continued)

The rear servo and governor pressure ports are at
the right rear of the transmission case. The overdrive
clutch pressure port is at the left rear of the case.
Test One - Transmission In Manual Low
This test checks pump output, pressure regulation,
and condition of the rear clutch and servo circuit.
Both test gauges are required for this test.
(1) Connect tachometer to engine. Position tachom-
eter so it can be observed from driver seat if helper
will be operating engine. Raise vehicle on hoist that
will allow rear wheels to rotate freely.
(2) Connect 100 psi Gauge C-3292 to accumulator
port. Then connect 300 psi Gauge C-3293-SP to rear
servo port.
(3) Disconnect throttle and gearshift cables from
levers on transmission valve body manual shaft.
(4) Have helper start and run engine at 1000 rpm.
(5) Move transmission shift lever fully forward
into 1 range.
(6) Gradually move transmission throttle lever
from full forward to full rearward position and note
pressures on both gauges:²Line pressure at accumulator port should be
54-60 psi (372-414 kPa) with throttle lever forward
and gradually increase to 90-96 psi (621-662 kPa) as
throttle lever is moved rearward.
²Rear servo pressure should be same as line pres-
sure within 3 psi (20.68 kPa).
Test Two - Transmission In 2 Range
This test checks pump output, line pressure and
pressure regulation. Use 100 psi Test Gauge C-3292
for this test.
(1) Leave vehicle in place on hoist and leave Test
Gauge C-3292 connected to accumulator port.
(2) Have helper start and run engine at 1000 rpm.
(3) Move transmission shift lever one detent rear-
ward from full forward position. This is 2 range.
(4) Move transmission throttle lever from full for-
ward to full rearward position and read pressure on
gauge.
(5) Line pressure should be 54-60 psi (372-414
kPa) with throttle lever forward and gradually
increase to 90-96 psi (621-662 kPa) as lever is moved
rearward.
Test Three - Transmission In D Range Third Gear
This test checks pressure regulation and condition
of the clutch circuits. Both test gauges are required
for this test.
(1) Turn OD switch off.
(2) Leave vehicle on hoist and leave Gauge C-3292
in place at accumulator port.
(3) Move Gauge C-3293-SP over to front servo port
for this test.
(4) Have helper start and run engine at 1600 rpm
for this test.
(5) Move transmission shift lever two detents rear-
ward from full forward position. This is D range.
(6) Read pressures on both gauges as transmission
throttle lever is gradually moved from full forward to
full rearward position:
²Line pressure at accumulator in D range third
gear, should be 54-60 psi (372-414 kPa) with throttle
lever forward and increase as lever is moved rear-
ward.
²Front servo pressure in D range third gear,
should be within 3 psi (21 kPa) of line pressure up to
kickdown point.
Test Four - Transmission In Reverse
This test checks pump output, pressure regulation
and the front clutch and rear servo circuits. Use 300
psi Test Gauge C-3293-SP for this test.
(1) Leave vehicle on hoist and leave gauge C-3292
in place at accumulator port.
(2) Move 300 psi Gauge C-3293-SP back to rear
servo port.
Fig. 9 Pressure Test Port Locations
1 - REAR SERVO TEST PORT
2 - GOVERNOR TEST PORT
3 - ACCUMULATOR TEST PORT
4 - FRONT SERVO TEST PORT
5 - OVERDRIVE CLUTCH TEST PORT
21 - 142 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)