automatic transmission DODGE RAM 2003 Service Repair Manual

AUTOMATIC TRANSMISSION - 48RE
TABLE OF CONTENTS
page page
AUTOMATIC TRANSMISSION - 48RE
DESCRIPTION........................312
OPERATION..........................314
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AUTOMATIC
TRANSMISSION.....................320
DIAGNOSIS AND TESTING - PRELIMINARY. . 320
DIAGNOSIS AND TESTING - ROAD
TESTING...........................320
DIAGNOSIS AND TESTING - HYDRAULIC
PRESSURE TEST....................321
DIAGNOSIS AND TESTING - AIR TESTING
TRANSMISSION CLUTCH AND BAND
OPERATION........................324
DIAGNOSIS AND TESTING - CONVERTER
HOUSING FLUID LEAK................324
DIAGNOSIS AND TESTING - DIAGNOSIS
CHARTS...........................325
STANDARD PROCEDURE - ALUMINUM
THREAD REPAIR.....................337
REMOVAL............................337
DISASSEMBLY........................339
CLEANING...........................345
INSPECTION.........................345
ASSEMBLY...........................346
INSTALLATION........................353
SCHEMATICS AND DIAGRAMS
HYDRAULIC SCHEMATICS.............355
SPECIFICATIONS
TRANSMISSION.....................368
SPECIAL TOOLS
RE TRANSMISSION..................370
ACCUMULATOR
DESCRIPTION........................372
OPERATION..........................373
INSPECTION.........................373
BANDS
DESCRIPTION........................373
OPERATION..........................374
ADJUSTMENTS
ADJUSTMENT - BANDS...............374
BRAKE TRANSMISSION SHIFT INTERLOCK
SYSTEM
DESCRIPTION........................375
OPERATION..........................375
DIAGNOSIS AND TESTING - BRAKE
TRANSMISSION SHIFT INTERLOCK......375
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK...................376ELECTRONIC GOVERNOR
DESCRIPTION........................376
OPERATION..........................377
REMOVAL............................378
INSTALLATION........................379
EXTENSION HOUSING SEAL
REMOVAL............................380
INSTALLATION........................380
FLUID AND FILTER
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL.............381
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID.......................381
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION....................381
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK............................381
STANDARD PROCEDURE - FLUID AND
FILTER REPLACEMENT...............383
STANDARD PROCEDURE - TRANSMISSION
FILL...............................383
FRONT CLUTCH
DESCRIPTION........................384
OPERATION..........................384
DISASSEMBLY........................384
INSPECTION.........................385
ASSEMBLY...........................386
FRONT SERVO
DESCRIPTION........................387
OPERATION..........................387
DISASSEMBLY........................388
CLEANING...........................388
INSPECTION.........................388
ASSEMBLY...........................388
GEARSHIFT CABLE
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE.............................389
REMOVAL............................389
INSTALLATION........................390
ADJUSTMENTS
GEARSHIFT CABLE..................391
OIL PUMP
DESCRIPTION........................392
OPERATION..........................392
DISASSEMBLY........................393
CLEANING...........................393
INSPECTION.........................393
ASSEMBLY...........................393
21 - 310 AUTOMATIC TRANSMISSION - 48REDR

OUTPUT SHAFT FRONT BEARING
REMOVAL............................395
INSTALLATION........................395
OUTPUT SHAFT REAR BEARING
REMOVAL............................395
INSTALLATION........................396
OVERDRIVE CLUTCH
DESCRIPTION........................396
OPERATION..........................396
OVERDRIVE SWITCH
DESCRIPTION........................397
OPERATION..........................397
DIAGNOSIS AND TESTING - OVERDRIVE
ELECTRICAL CONTROLS..............397
REMOVAL............................397
INSTALLATION........................397
OVERDRIVE UNIT
REMOVAL............................398
DISASSEMBLY........................399
CLEANING...........................405
INSPECTION.........................406
ASSEMBLY...........................406
INSTALLATION........................414
OVERRUNNING CLUTCH CAM/OVERDRIVE
PISTON RETAINER
DESCRIPTION........................415
OPERATION..........................415
DISASSEMBLY........................415
CLEANING...........................416
INSPECTION.........................416
ASSEMBLY...........................416
PISTONS
DESCRIPTION........................418
OPERATION..........................418
PLANETARY GEARTRAIN/OUTPUT SHAFT
DESCRIPTION........................420
OPERATION..........................420
DISASSEMBLY........................421
INSPECTION.........................422
ASSEMBLY...........................423
REAR CLUTCH
DESCRIPTION........................426
OPERATION..........................427
DISASSEMBLY........................427
CLEANING...........................428
INSPECTION.........................428
ASSEMBLY...........................428REAR SERVO
DESCRIPTION........................429
OPERATION..........................429
DISASSEMBLY........................430
CLEANING...........................430
ASSEMBLY...........................430
SHIFT MECHANISM
DESCRIPTION........................430
OPERATION..........................430
SOLENOID
DESCRIPTION........................431
OPERATION..........................431
SPEED SENSOR
DESCRIPTION........................431
OPERATION..........................431
THROTTLE VALVE CABLE
DESCRIPTION........................432
ADJUSTMENTS - THROTTLE VALVE CABLE . 432
TORQUE CONVERTER
DESCRIPTION........................434
OPERATION..........................438
REMOVAL............................439
INSTALLATION........................439
TORQUE CONVERTER DRAINBACK VALVE
DESCRIPTION........................440
OPERATION..........................440
STANDARD PROCEDURE - TORQUE
CONVERTER DRAINBACK VALVE........440
TRANSMISSION RANGE SENSOR
DESCRIPTION........................441
OPERATION..........................441
DIAGNOSIS AND TESTING - TRANSMISSION
RANGE SENSOR (TRS)................442
REMOVAL............................443
INSTALLATION........................444
TRANSMISSION TEMPERATURE SENSOR
DESCRIPTION........................445
OPERATION..........................445
VALVE BODY
DESCRIPTION........................445
OPERATION..........................450
REMOVAL............................464
DISASSEMBLY........................465
CLEANING...........................476
INSPECTION.........................476
ASSEMBLY...........................477
INSTALLATION........................486
ADJUSTMENTS - VALVE BODY...........487
DRAUTOMATIC TRANSMISSION - 48RE 21 - 311

AUTOMATIC TRANSMISSION -
48RE
DESCRIPTION
The 48RE (Fig. 1) is a four speed fully automatic
transmission 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 - 312 AUTOMATIC TRANSMISSION - 48REDR

Fig. 1 48RE Transmission
DRAUTOMATIC TRANSMISSION - 48RE 21 - 313
AUTOMATIC TRANSMISSION - 48RE (Continued)

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 transmission
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 converter 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 And Serial Number
Location
1 - PART NUMBER
2 - BUILD DATE
3 - SERIAL NUMBER
21 - 314 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

PARK POWERFLOW
As the engine is running and the crankshaft is
rotating, the flexplate and torque converter, which
are also bolted to it, are all rotating in a clockwise
direction as viewed from the front of the engine. The
notched hub of the torque converter is connected to
the oil pump's internal gear, supplying the transmis-
sion with oil pressure. As the converter turns, it
turns the input shaft in a clockwise direction. As the
input shaft is rotating, the front clutch hub-rear
clutch retainer and all their associated parts are also
rotating, all being directly connected to the input
shaft. The power flow from the engine through the
front clutch hub and rear clutch retainer stops at the
rear clutch retainer. Therefore, no power flow to the
output shaft occurs because no clutches are applied.
The only mechanism in use at this time is the park-
ing sprag (Fig. 3), which locks the parking gear on
the output shaft to the transmission case.
NEUTRAL POWERFLOW
With the gear selector in the NEUTRAL position
(Fig. 4), the power flow of the transmission is essen-
tially the same as in the park position. The only
operational difference is that the parking sprag has
been disengaged, unlocking the output shaft from the
transmission case and allowing it to move freely.
Fig. 3 Park Powerflow
1 - PAWL ENGAGED FOR PARK
2 - PARK SPRAG
3 - OUTPUT SHAFT
Fig. 4 Neutral Powerflow
1 - PAWL DISENGAGED FOR NEUTRAL
2 - PARK SPRAG
3 - OUTPUT SHAFT
4 - CAM
5-PAWL
DRAUTOMATIC TRANSMISSION - 48RE 21 - 315
AUTOMATIC TRANSMISSION - 48RE (Continued)

REVERSE POWERFLOW
When the gear selector is moved into the
REVERSE position (Fig. 5), the front clutch and the
rear band are applied. With the application of the
front clutch, engine torque is applied to the sun gear,
turning it in a clockwise direction. The clockwise
rotation of the sun gear causes the rear planet pin-
ions to rotate against engine rotation in a counter-
clockwise direction. The rear band is holding the low
reverse drum, which is splined to the rear carrier.
Since the rear carrier is being held, the torque from
the planet pinions is transferred to the rear annulusgear, which is splined to the output shaft. The output
shaft in turn rotates with the annulus gear in a
counterclockwise direction giving a reverse gear out-
put. The entire transmission of torque is applied to
the rear planetary gearset only. Although there is
torque input to the front gearset through the sun
gear, no other member of the gearset is being held.
During the entire reverse stage of operation, the
front planetary gears are in an idling condition.
Fig. 5 Reverse Powerflow
1 - FRONT CLUTCH ENGAGED 5 - OUTPUT SHAFT
2 - OUTPUT SHAFT 6 - INPUT SHAFT
3 - LOW/REVERSE BAND APPLIED 7 - FRONT CLUTCH ENGAGED
4 - INPUT SHAFT 8 - LOW/REVERSE BAND APPLIED
21 - 316 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

FIRST GEAR POWERFLOW
When the gearshift lever is moved into the DRIVE
position the transmission goes into first gear (Fig. 6).
As soon as the transmission is shifted from PARK or
NEUTRAL to DRIVE, the rear clutch applies, apply-
ing the rear clutch pack to the front annulus gear.
Engine torque is now applied to the front annulus
gear turning it in a clockwise direction. With the
front annulus gear turning in a clockwise direction, it
causes the front planets to turn in a clockwise direc-
tion. The rotation of the front planets cause the sun
to revolve in a counterclockwise direction. The sun
gear now transfers its counterclockwise rotation tothe rear planets which rotate back in a clockwise
direction. With the rear annulus gear stationary, the
rear planet rotation on the annulus gear causes the
rear planet carrier to revolve in a counterclockwise
direction. The rear planet carrier is splined into the
low-reverse drum, and the low reverse drum is
splined to the inner race of the over-running clutch.
With the over-running clutch locked, the planet car-
rier is held, and the resulting torque provided by the
planet pinions is transferred to the rear annulus
gear. The rear annulus gear is splined to the output
shaft and rotated along with it (clockwise) in an
underdrive gear reduction mode.
Fig. 6 First Gear Powerflow
1 - OUTPUT SHAFT 5 - OVER-RUNNING CLUTCH HOLDING
2 - OVER-RUNNING CLUTCH HOLDING 6 - INPUT SHAFT
3 - REAR CLUTCH APPLIED 7 - REAR CLUTCH APPLIED
4 - OUTPUT SHAFT 8 - INPUT SHAFT
DRAUTOMATIC TRANSMISSION - 48RE 21 - 317
AUTOMATIC TRANSMISSION - 48RE (Continued)

SECOND GEAR POWERFLOW
In DRIVE-SECOND (Fig. 7), the same elements
are applied as in MANUAL-SECOND. Therefore, the
power flow will be the same, and both gears will be
discussed as one in the same. In DRIVE-SECOND,
the transmission has proceeded from first gear to its
shift point, and is shifting from first gear to second.
The second gear shift is obtained by keeping the rear
clutch applied and applying the front (kickdown)
band. The front band holds the front clutch retainer
that is locked to the sun gear driving shell. With the
rear clutch still applied, the input is still on the front
annulus gear turning it clockwise at engine speed.Now that the front band is holding the sun gear sta-
tionary, the annulus rotation causes the front planets
to rotate in a clockwise direction. The front carrier is
then also made to rotate in a clockwise direction but
at a reduced speed. This will transmit the torque to
the output shaft, which is directly connected to the
front planet carrier. The rear planetary annulus gear
will also be turning because it is directly splined to
the output shaft. All power flow has occurred in the
front planetary gear set during the drive-second
stage of operation, and now the over-running clutch,
in the rear of the transmission, is disengaged and
freewheeling on its hub.
Fig. 7 Second Gear Powerflow
1 - KICKDOWN BAND APPLIED 6 - INPUT SHAFT
2 - OUTPUT SHAFT 7 - REAR CLUTCH APPLIED
3 - REAR CLUTCH ENGAGED 8 - KICKDOWN BAND APPLIED
4 - OUTPUT SHAFT 9 - INPUT SHAFT
5 - OVER-RUNNING CLUTCH FREE-WHEELING
21 - 318 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 frontannulus 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.
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 - 319
AUTOMATIC TRANSMISSION - 48RE (Continued)