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(12) Fill transmission with recommended fluid and
road test vehicle to verify repair.
INSTALLATION
(1) Check condition of O-ring seals on valve body harness connector (Fig. 343). Replace seals on con- nector body if cut or worn.
(2) Check condition of manual lever shaft seal in transmission case. Replace seal if lip is cut or worn. Install new seal with 15/16 deep well socket (Fig. 344).
(3) Check condition of seals on accumulator piston.
Install new piston seals, if necessary.
(4) Verify that transmission range sensor is NOT installed. Valve body cannot be installed with sensor in place.
(5) Place valve body manual lever in low (1 posi- tion) so ball on park lock rod will be easier to install in sprag.
(6) Lubricate shaft of manual lever with petroleum jelly. This will ease inserting shaft through seal in case.
(7) Lubricate seal rings on valve body harness con-
nector with petroleum jelly.
(8) Position valve body in case and work end of park lock rod into and through pawl sprag. Turn pro- peller shaft to align sprag and park lock teeth if nec- essary. The rod will click as it enters pawl. Move rod to check engagement.
CAUTION: It is possible for the park rod to displace into a cavity just above the pawl sprag during installation. Make sure the rod is actually engaged in the pawl and has not displaced into this cavity.
(9) Install accumulator spring and piston into case. Then swing valve body over piston and outer spring to hold it in place.
(10) Align accumulator piston and outer spring, manual lever shaft and electrical connector in case. (11) Then seat valve body in case and install one
or two bolts to hold valve body in place.
(12) Tighten valve body bolts alternately and
evenly to 11 N·m (100 in. lbs.) torque.
(13) Install new fluid filter on valve body. Tighten
filter screws to 4 N·m (35 in. lbs.) torque.
(14) Install throttle and gearshift levers on valve
body manual lever shaft.
21 - 308
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 46RE
DR
(15) Check and adjust front and rear bands if nec-
essary.
(16) Connect solenoid case connector wires. (17) Install the transmission range sensor. (18) Install oil pan and new gasket. Tighten pan
bolts to 17 N·m (13 ft. lbs.) torque.
(19) Lower vehicle and fill
transmission with
Mopart ATF +4, Automatic Transmission fluid.
(20) Check and adjust gearshift and throttle valve
cables, if necessary.
Fig.343ValveBodyHarnessConnectorO-RingSeal 1 - CONNECTOR O-RINGS 2 - VALVE BODY HARNESS CONNECTOR 3 - HARNESS
ADJUSTMENTS - VALVE BODY
CONTROL PRESSURE ADJUSTMENTS
valve body;
There are two control pressure adjustments on the †Line Pressure †Throttle Pressure Line and throttle pressures are interdependent because each affects shift quality and timing. As a result, both adjustments must be performed properly and in the correct sequence. Adjust line pressure first and throttle pressure last.
LINE PRESSURE ADJUSTMENT
Measure distance from the valve body to the inner edge of the adjusting screw with an accurate steel scale (Fig. 345).
Distance should be 33.4 mm (1-5/16 in.). If adjustment is required, turn the adjusting screw
in, or out, to obtain required distance setting.
NOTE: The 33.4 mm (1-5/16 in.) setting is an approximate setting. Manufacturing tolerances may make it necessary to vary from this dimension to obtain desired pressure.
One complete turn of the adjusting screw changes
line pressure approximately 1-2/3 psi (9 kPa).
Turning the adjusting screw counterclockwise increases pressure while turning the screw clockwise decreases pressure.
Fig.344ManualLeverShaftSeal
1 - 15/1688 SOCKET 2 - SEAL
Fig.345LinePressureAdjustment
1 - WRENCH 2 - 1–5/16 INCH
DR VALVE BODY (Continued)
THROTTLE PRESSURE ADJUSTMENT
AUTOMATIC TRANSMISSION - 46RE
21 - 309
Insert Gauge Tool C-3763 between the throttle
lever cam and the kickdown valve stem (Fig. 346).
Push the gauge tool inward to compress the kick- down valve against the spring and bottom the throt- tle valve.
Maintain pressure against kickdown valve spring. Turn throttle lever stop screw until the screw head touches throttle lever tang and the throttle lever cam touches gauge tool.
NOTE: The kickdown valve spring must be fully compressed and the kickdown valve completely bottomed to obtain correct adjustment.
Fig.346ThrottlePressureAdjustment
1 - HEX WRENCH (IN THROTTLE LEVER ADJUSTING SCREW) 2 - SPECIAL TOOL C-3763 (POSITIONED BETWEEN THROTTLE LEVER AND KICKDOWN VALVE)
21 - 310
AUTOMATIC TRANSMISSION - 48RE
AUTOMATIC TRANSMISSION - 48RE
TABLE OF CONTENTS
page
DR
page
AUTOMATIC TRANSMISSION - 48RE
ELECTRONIC GOVERNOR
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 312
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 314
DIAGNOSIS AND TESTINGDIAGNOSIS AND TESTING - AUTOMATIC
TRANSMISSION . . . . . . . . . . . . . . . . . . . . . 320
DIAGNOSIS AND TESTING - PRELIMINARY . . 320
DIAGNOSIS AND TESTING - ROADTESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
DIAGNOSIS AND TESTING - HYDRAULIC
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 376
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 377
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 379EXTENSION HOUSING SEAL
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 380FLUID AND FILTER
DIAGNOSIS AND TESTING
PRESSURE TEST . . . . . . . . . . . . . . . . . . . . 321
DIAGNOSIS AND TESTING - EFFECTS OF
DIAGNOSIS AND TESTING - AIR TESTING
TRANSMISSION CLUTCH AND BAND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . 324
DIAGNOSIS AND TESTING - CONVERTER
INCORRECT FLUID LEVEL . . . . . . . . . . . . . 381
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID . . . . . . . . . . . . . . . . . . . . . . . 381
DIAGNOSIS AND TESTING - FLUID
HOUSING FLUID LEAK . . . . . . . . . . . . . . . . 324
CONTAMINATION . . . . . . . . . . . . . . . . . . . . 381
DIAGNOSIS AND TESTING - DIAGNOSIS
STANDARD PROCEDURE
CHARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
STANDARD PROCEDURE - FLUID LEVEL
. . . . . . . . . . . . . . . . . . . . . 368
FRONT SERVO
STANDARD PROCEDURE - ALUMINUM
THREAD REPAIR . . . . . . . . . . . . . . . . . . . . . 337
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 339
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 345
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 353
SCHEMATICS AND DIAGRAMSHYDRAULIC SCHEMATICS . . . . . . . . . . . . . 355
SPECIFICATIONS TRANSMISSION
SPECIAL TOOLS
RE TRANSMISSION
. . . . . . . . . . . . . . . . . . 370
ACCUMULATOR
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 372
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 373
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 373BANDS
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 373
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 374
ADJUSTMENTSADJUSTMENT - BANDS
. . . . . . . . . . . . . . . 374
BRAKE TRANSMISSION SHIFT INTERLOCK
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 375
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 375
DIAGNOSIS AND TESTING - BRAKETRANSMISSION SHIFT INTERLOCK . . . . . . 375
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK
. . . . . . . . . . . . . . . . . . . 376
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . 386DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 387
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 387
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 388
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 388
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 388
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 388GEARSHIFT CABLE
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 390
ADJUSTMENTSGEARSHIFT CABLE
. . . . . . . . . . . . . . . . . . 391
OIL PUMP
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 392
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 392
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 393
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 393
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 393DR
AUTOMATIC TRANSMISSION - 48RE
21 - 311
OUTPUT SHAFT FRONT BEARING
REAR SERVO
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 395OUTPUT SHAFT REAR BEARING
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 396DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 429
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 429
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 430
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 430OVERDRIVE CLUTCH
SHIFT MECHANISM
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 396
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 396DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 430
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 430OVERDRIVE SWITCH
SOLENOID
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 397
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 397
DIAGNOSIS AND TESTING - OVERDRIVEELECTRICAL CONTROLS
. . . . . . . . . . . . . . 397
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 397OVERDRIVE UNIT
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 399
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 406
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 406
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 414DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 431
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 431SPEED SENSOR
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 431
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 431THROTTLE VALVE CABLE
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 432
ADJUSTMENTS - THROTTLE VALVE CABLE . 432TORQUE CONVERTER
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 434
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 438
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 439OVERRUNNING CLUTCH CAM/OVERDRIVE
TORQUE CONVERTER DRAINBACK VALVE
PISTON RETAINER DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 415
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 415
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 415
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 416
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 416PISTONS
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 418
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 418PLANETARY GEARTRAIN/OUTPUT SHAFT
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 420
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 420
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 421
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 422
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 423REAR CLUTCH
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 426
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 427
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 427
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 428
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 428DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 440
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 440
STANDARD PROCEDURE - TORQUECONVERTER DRAINBACK VALVE . . . . . . . . 440
TRANSMISSION RANGE SENSOR
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 441
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 441
DIAGNOSIS AND TESTING - TRANSMISSIONRANGE SENSOR (TRS)
. . . . . . . . . . . . . . . . 442
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 444TRANSMISSION TEMPERATURE SENSOR
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 445
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 445VALVE BODY
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . 445
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . 450
REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . 465
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . 476
ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 486
ADJUSTMENTS - VALVE BODY . . . . . . . . . . . 48721 - 312
AUTOMATIC TRANSMISSION - 48RE
DR
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 the
low/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.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 313
21 - 314
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
1 - TORQUE CONVERTER 2 - INPUT SHAFT 3 - OIL PUMP 4 - FRONT BAND 5 - FRONT CLUTCH 6 - REAR CLUTCH 7 - PLANETARIES 8 - REAR BAND 9 - OVERRUNNING CLUTCH
10 - OVERDRIVE CLUTCH 11 - DIRECT CLUTCH 12 - PLANETARY GEAR 13 - INTERMEDIATE SHAFT 14 - OVERDRIVE OVERRUNNING CLUTCH 15 - DIRECT CLUTCH SPRING 16 - OVERDRIVE PISTON RETAINER 17 - OIL PAN 18 - VALVE BODY
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.
Fig.2TransmissionPartAndSerialNumber
Location
1 - PART NUMBER 2 - BUILD DATE 3 - SERIAL NUMBER
GEAR RATIOS
The 48RE gear ratios are:
1st . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.45:1
2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.45:1
3rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.00:1
4th . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.69:1
Rev. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.20:1OPERATION
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.
DR AUTOMATIC TRANSMISSION - 48RE (Continued) PARK POWERFLOW
NEUTRAL POWERFLOW
AUTOMATIC TRANSMISSION - 48RE
21 - 315
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.
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.
Fig.4NeutralPowerflow
1 - PAWL DISENGAGED FOR NEUTRAL 2 - PARK SPRAG 3 - OUTPUT SHAFT 4 - CAM 5 - PAWL
Fig.3ParkPowerflow
1 - PAWL ENGAGED FOR PARK 2 - PARK SPRAG 3 - OUTPUT SHAFT
AUTOMATIC TRANSMISSION - 48RE
21 - 316
AUTOMATIC TRANSMISSION - 48RE (Continued) REVERSE POWERFLOWselector
is moved into
When the gear
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 annulus
DR
gear, 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.
1 - FRONT CLUTCH ENGAGED 2 - OUTPUT SHAFT 3 - LOW/REVERSE BAND APPLIED 4 - INPUT SHAFT
Fig.5ReversePowerflow
5 - OUTPUT SHAFT 6 - INPUT SHAFT 7 - FRONT CLUTCH ENGAGED 8 - LOW/REVERSE BAND APPLIED
AUTOMATIC TRANSMISSION - 48RE
21 - 317
DR 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 to
the 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.
1 - OUTPUT SHAFT 2 - OVER-RUNNING CLUTCH HOLDING 3 - REAR CLUTCH APPLIED 4 - OUTPUT SHAFT
5 - OVER-RUNNING CLUTCH HOLDING 6 - INPUT SHAFT 7 - REAR CLUTCH APPLIED 8 - INPUT SHAFT
Fig.6FirstGearPowerflow
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AUTOMATIC TRANSMISSION - 48RE
21 - 318
AUTOMATIC TRANSMISSION - 48RE (Continued) SECOND GEAR POWERFLOWIn 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.
1 - KICKDOWN BAND APPLIED 2 - OUTPUT SHAFT 3 - REAR CLUTCH ENGAGED 4 - OUTPUT SHAFT 5 - OVER-RUNNING CLUTCH FREE-WHEELING
Fig.7SecondGearPowerflow 6 - INPUT SHAFT 7 - REAR CLUTCH APPLIED 8 - KICKDOWN BAND APPLIED 9 - INPUT SHAFT
AUTOMATIC TRANSMISSION - 48RE
21 - 319
DR AUTOMATIC TRANSMISSION - 48RE (Continued) DIRECT DRIVE POWERFLOW
takes place,
The vehicle has accelerated and reached the shift point for the 2-3 upshift into direct drive (Fig. 8). When the shift 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.
1 - FRONT CLUTCH APPLIED 2 - OVER-RUNNING CLUTCH FREE-WHEELING 3 - OUTPUT SHAFT 4 - REAR CLUTCH APPLIED 5 - OUTPUT SHAFT
Fig.8DirectDrivePowerflow 6 - INPUT SHAFT 7 - OVER-RUNNING CLUTCH FREE-WHEELING 8 - REAR CLUTCH APPLIED 9 - FRONT CLUTCH APPLIED 10 - INPUT SHAFT
AUTOMATIC TRANSMISSION - 48RE
21 - 320
AUTOMATIC TRANSMISSION - 48RE (Continued) FOURTH GEAR POWERFLOWVEHICLE IS DRIVEABLE
DR
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 overdrive 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 valve moves the overdrive piston into contact with the overdrive clutch. The direct clutch is disengaged before the overdrive clutch is engaged. The boost valve provides increased fluid apply pressure to the overdrive clutch during 3-4 upshifts, and when accel- erating in fourth gear. The 3-4 accumulator cushions overdrive clutch engagement to smooth 3-4 upshifts. The accumulator is charged at the same time as apply pressure acts against the overdrive piston.DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AUTOMATIC TRANSMISSION
Automatic transmission problems can be a result of poor engine performance, incorrect fluid level, incor- rect linkage or cable adjustment, band or hydraulic control pressure adjustments, hydraulic system mal- functions or electrical/mechanical component mal- functions. Begin diagnosis by checking the easily accessible items such as: fluid level and condition, linkage adjustments and electrical connections. A road test will determine if further diagnosis is neces- sary.
DIAGNOSIS AND TESTING - PRELIMINARY
Two basic procedures are required. One procedure for vehicles that are drivable and an alternate proce- dure for disabled vehicles (will not back up or move forward).
(1) Check for transmission fault codes using DRBt
scan tool.
(2) Check fluid level and condition. (3) Adjust throttle and gearshift linkage if com- plaint was based on delayed, erratic, or harsh shifts. (4) Road test and note how transmission upshifts,
downshifts, and engages.
(5) Perform hydraulic pressure test if shift prob-
lems were noted during road test.
(6) Perform air-pressure test to check clutch-band
operation.
VEHICLE IS DISABLED
(1) Check fluid level and condition. (2) Check for broken or disconnected gearshift or
throttle linkage.
(3) Check for cracked, leaking cooler lines, or loose
or missing pressure-port plugs.
(4) Raise and support vehicle on safety stands, start engine, shift transmission into gear, and note following:
(a) If propeller shaft turns but wheels do not,
problem is with differential or axle shafts.
(b) If propeller shaft does not turn and transmis- sion is noisy, stop engine. Remove oil pan, and check for debris. If pan is clear, remove transmis- sion and check for damaged drive plate, converter, oil pump, or input shaft.
(c) If propeller shaft does not turn and transmis- sion is not noisy, perform hydraulic-pressure test to determine if problem is hydraulic or mechanical.
DIAGNOSIS AND TESTING - ROAD TESTING
Before road testing, be sure the fluid level and con- trol cable adjustments have been checked and adjusted if necessary. Verify that diagnostic trouble codes have been resolved.
Observe engine performance during the road test. A poorly tuned engine will not allow accurate analy- sis of transmission operation.
Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage. Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means clutch, band or overrunning clutch problems. If the condition is advanced, an overhaul will be necessary to restore normal operation.
A slipping clutch or band can often be determined by comparing which internal units are applied in the various gear ranges. The Clutch and Band Applica- tion chart provides a basis for analyzing road test results.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 321
CLUTCH AND BAND APPLICATION CHART
SHIFT LEVER
POSITION
Reverse Drive - First Drive - Second Drive - Third Drive - Fourth Manual Second Manual
First
TRANSMISSION CLUTCHES AND BANDS
OVERDRIVE CLUTCHES
FRONT CLUTCH
FRONT BAND
REAR
CLUTCH
REAR BAND
OVER-
RUNNING CLUTCH
OVER- DRIVE CLUTCH
DIRECT CLUTCH
OVER-
RUNNING CLUTCH
Note that the rear clutch is applied in all forward ranges (D, 2, 1). The transmission overrunning clutch is applied in first gear (D, 2 and 1 ranges) only. The rear band is applied in 1 and R range only.
Note that the overdrive clutch is applied only in fourth gear and the overdrive direct clutch and over- running clutch are applied in all ranges except fourth gear.
For example: If slippage occurs in first gear in D and 2 range but not in 1 range, the transmission overrunning clutch is faulty. Similarly, if slippage occurs in any two forward gears, the rear clutch is slipping.
Applying the same method of analysis, note that the front and rear clutches are applied simulta- neously only in D range third and fourth gear. If the transmission slips in third gear, either the front clutch or the rear clutch is slipping.
If the transmission slips in fourth gear but not in third gear, the overdrive clutch is slipping. By select- ing another gear which does not use these clutches, the slipping unit can be determined. For example, if the transmission also slips in Reverse, the front clutch is slipping. If the transmission does not slip in Reverse, the rear clutch is slipping.
If slippage occurs during the 3-4 shift or only in fourth gear, the overdrive clutch is slipping. Simi- larly, if the direct clutch were to fail, the transmis- sion would lose both reverse gear and overrun braking in 2 position (manual second gear).
If the transmission will not shift to fourth gear, the control switch, overdrive solenoid or related wiring may also be the problem cause.
This process of elimination can be used to identify a slipping unit and check operation. Proper use of the Clutch and Band Application Chart is the key.
Although road test analysis will help determine the slipping unit, the actual cause of a malfunction usu- ally cannot be determined until hydraulic and air pressure tests are performed. Practically any condi- tion can be caused by leaking hydraulic circuits or sticking valves.
Unless a malfunction is obvious, such as no drive in D range first gear, do not disassemble the trans- mission. Perform the hydraulic and air pressure tests to help determine the probable cause.
DIAGNOSIS AND TESTING - HYDRAULIC PRESSURE TEST
Hydraulic test pressures range from a low of one psi (6.895 kPa) governor pressure, to 300 psi (2068
kPa) at the rear servo pressure port in reverse.An accurate tachometer and pressure test gauges are required. Test Gauge C-3292 has a 100 psi range and is used at the accumulator, governor, and front servo ports. Test Gauge C-3293-SP has a 300 psi range and is used at the rear servo and overdrive ports where pressures exceed 100 psi.
Pressure Test Port Locations
Test ports are located at both sides of the transmis-
sion case (Fig. 9).
Line pressure is checked at the accumulator port on the right side of the case. The front servo pressure port is at the right side of the case just behind the filler tube opening.
21 - 322
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
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.
†Line 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. †Rear 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
Fig.9PressureTestPortLocations
1 - REAR SERVO TEST PORT 2 - GOVERNOR TEST PORT 3 - ACCUMULATOR TEST PORT 4 - FRONT SERVO TEST PORT 5 - OVERDRIVE CLUTCH TEST PORT
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:
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
(4) Have helper start and run engine at 1600 rpm
for this test.
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: †Line 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.†Front 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.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 323
(3) Have helper start and run engine at 1600 rpm
for test.
(4) Move transmission shift
lever four detents rearward from full forward position. This is Reverse range.
(5) Move transmission throttle lever fully forward then fully rearward and note reading at Gauge C-3293-SP.
(6) Pressure should be 145 - 175 psi (1000-1207
kPa) with throttle lever forward and increase to 230 - 280 psi (1586-1931 kPa) as lever is gradually moved rearward.Test Five - Governor Pressure
This test checks governor operation by measuring governor pressure response to changes in vehicle speed. It is usually not necessary to check governor operation unless shift speeds are incorrect or if the transmission will not downshift. The test should be performed on the road or on a hoist that will allow the rear wheels to rotate freely.
(1) Move 100 psi Test Gauge C-3292 to governor
pressure port.
(2) Move transmission shift lever two detents rear-
ward from full forward position. This is D range.
(3) Have helper start and run engine at curb idle speed. Then firmly apply service brakes so wheels will not rotate.
(4) Note governor pressure: †Governor pressure should be no more than 20.6
kPa (3 psi) at curb idle speed and wheels not rotat- ing.†If pressure exceeds 20.6 kPa (3 psi), a fault exists in governor pressure control system. (5) Release brakes, slowly increase engine speed, and observe speedometer and pressure test gauge (do not exceed 30 mph on speedometer). Governor pres- sure should increase in proportion to vehicle speed. Or approximately 6.89 kPa (1 psi) for every 1 mph. (6) Governor pressure rise should be smooth and drop back to no more than 20.6 kPa (3 psi), after engine returns to curb idle and brakes are applied to prevent wheels from rotating.(7) Compare results of pressure test with analysis
chart.
Test Six - Transmission In Overdrive Fourth Gear
This test checks line pressure at the overdrive clutch in fourth gear range. Use 300 psi Test Gauge C-3293-SP for this test. The test should be performed on the road or on a chassis dyno.
(1) Remove tachometer; it is not needed for this
test.
(2) Move 300 psi Gauge to overdrive clutch pres- sure test port. Then remove other gauge and reinstall test port plug.
(3) Lower vehicle. (4) Turn OD switch on. (5) Secure test gauge so it can be viewed from
drivers seat.
(6) Start engine and shift into D range. (7) Increase vehicle speed gradually until 3-4 shift
occurs and note gauge pressure.
(8) Pressure should be 524-565 kPa (76-82 psi) with closed throttle and increase to 690-896 kPa (100-130 psi) at 1/2 to 3/4 throttle. Note that pres- sure can increase to around 965 kPa (140 psi) at full throttle.
(9) Return to shop or move vehicle off chassis
dyno.
PRESSURE TEST ANALYSIS CHART
TEST CONDITION
INDICATION
Line pressure OK during any one test Line pressure OK in R but low in D, 2, 1
Pressure low in D Fourth Gear Range
Pressure OK in 1, 2 but low in D3 and R Pressure OK in 2 but low in R and 1
Front servo pressure in 2Pressure low in all positions
Governor pressure too high at idle speed
Governor pressure low at all mph figures
Lubrication pressure low at all throttle positions
Line pressure high
Line pressure low
Pump and regulator valve OK Leakage in rear clutch area (seal rings, clutch seals) Overdrive clutch piston seal, or check ball problem Leakage in front clutch area Leakage in rear servo
Leakage in servo; broken servo ring or cracked servo piston Clogged filter, stuck regulator valve, worn or faulty pump, low oil level Governor pressure solenoid valve system fault. Refer to diagnostic book. Faulty governor pressure solenoid, transmission control module, or governor pressure sensor Clogged fluid cooler or lines, seal rings leaking, worn pump bushings, pump, clutch retainer, or clogged filter. Output shaft plugged, sticky regulator valve Sticky regulator valve, clogged filter, worn pump
AUTOMATIC TRANSMISSION - 48RE
21 - 324
AUTOMATIC TRANSMISSION - 48RE (Continued) DIAGNOSIS AND TESTING - AIR TESTING TRANSMISSION CLUTCH AND BAND OPERATIONAir-pressure testing can be used to check transmis- sion front/rear clutch and band operation. The test can be conducted with the transmission either in the vehicle or on the work bench, as a final check, after overhaul.
Air-pressure testing requires that the oil pan and valve body be removed from the transmission. The servo and clutch apply passages are shown (Fig. 10).
Fig.10AirPressureTestPassages
1 - LINE PRESSURE TO ACCUMULATOR 2 - REAR SERVO APPLY 3 - FRONT SERVO APPLY 4 - FRONT SERVO RELEASE 5 - PUMP SUCTION 6 - PUMP PRESSURE 7 - FRONT CLUTCH APPLY 8 - REAR CLUTCH APPLY 9 - TO TORQUE CONVERTOR 10 - TO COOLER 11 - FROM TORQUE CONVERTER
Front Clutch Air Test
Place one or two fingers on the clutch housing and apply air pressure through front clutch apply pas- sage. Piston movement can be felt and a soft thump heard as the clutch applies.
DR
Rear Clutch Air Test
Place one or two fingers on the clutch housing and apply air pressure through rear clutch apply passage. Piston movement can be felt and a soft thump heard as the clutch applies.
Front Servo Air Test
Apply air pressure to the front servo apply pas- sage. The servo rod should extend and cause the band to tighten around the drum. Spring pressure should release the servo when air pressure is removed.
Rear Servo Air Test
Apply air pressure to the rear servo apply passage. The servo rod should extend and cause the band to tighten around the drum. Spring pressure should release the servo when air pressure is removed.
DIAGNOSIS AND TESTING - CONVERTER HOUSING FLUID LEAK
When diagnosing converter housing fluid leaks,
two items must be established before repair.
(1) Verify that a leak condition actually exists. (2) Determined the true source of the leak. Some suspected converter housing fluid leaks may not be leaks at all. They may only be the result of residual fluid in the converter housing, or excess fluid spilled during factory fill or fill after repair. Converter housing leaks have several potential sources. Through careful observation, a leak source can be identified before removing the transmission for repair. Pump seal leaks tend to move along the drive hub and onto the rear of the converter. Pump body leaks follow the same path as a seal leak (Fig. 11). Pump vent or pump attaching bolt leaks are gen- erally deposited on the inside of the converter hous- ing and not on the converter itself (Fig. 11). Pump o-ring or gasket leaks usually travel down the inside of the converter housing. Front band lever pin plug leaks are generally deposited on the housing and not on the converter.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 325
(4) Inspect pump bushing and converter hub. If bushing is scored, replace it. If converter hub is scored, either polish it with crocus cloth or replace converter.
(5) Install new pump seal, O-ring, and gasket. Replace oil pump if cracked, porous or damaged in any way. Be sure to loosen the front band before installing the oil pump, damage to the oil pump seal may occur if the band is still tightened to the front clutch retainer.
(6) Loosen kickdown lever pin access plug three turns. Apply Loctite™ 592, or Permatext No. 2 to plug threads and tighten plug to 17 N·m (150 in. lbs.) torque.
(7) Adjust front band. (8) Lubricate pump seal and converter hub with transmission fluid or petroleum jelly and install con- verter.
transmission and converter housing
(9) Install dust shield.
(10) Lower vehicle.
DIAGNOSIS AND TESTING - DIAGNOSIS CHARTS
The diagnosis charts provide additional reference when diagnosing a transmission fault. The charts provide general information on a variety of transmis- sion, overdrive unit and converter clutch fault condi- tions.
The hydraulic flow charts in the Schematics and Diagrams section of this group, outline fluid flow and hydraulic circuitry. Circuit operation is provided for PARK, NEUTRAL, FIRST, SECOND, THIRD, FOURTH, MANUAL FIRST, MANUAL SECOND, and REVERSE gear ranges. Normal working pres- sures are also supplied for each of the gear ranges.
Fig.11ConverterHousingLeakPaths
1 - PUMP SEAL 2 - PUMP VENT 3 - PUMP BOLT 4 - PUMP GASKET 5 - CONVERTER HOUSING 6 - CONVERTER 7 - REAR MAIN SEAL LEAK
TORQUE CONVERTER LEAK POINTS
Possible sources of converter leaks are: †Leaks at the weld joint around the outside diam- †Leaks at the converter hub weld.
eter weld.
CONVERTER HOUSING AREA LEAK CORRECTION
(1) Remove converter. (2) Tighten front band adjusting screw until band is tight around front clutch retainer. This prevents front/rear clutches from coming out when oil pump is removed.
(3) Remove oil pump and remove pump seal. Inspect pump housing drainback and vent holes for obstructions. Clear holes with solvent and wire.
21 - 326
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DIAGNOSIS CHARTS
DR
CONDITION
POSSIBLE CAUSES
CORRECTION
HARSH ENGAGEMENT (FROM NEUTRAL TO DRIVE OR REVERSE)
1. Fluid Level Low. 2. Throttle Linkage Mis-adjusted. 3. Mount and Driveline Bolts Loose.
DELAYED ENGAGEMENT (FROM NEUTRAL TO DRIVE OR REVERSE)
4. U-Joint Worn/Broken.
5. Axle Backlash Incorrect.
6. Hydraulic Pressure Incorrect.
7. Band Mis-adjusted. 8. Valve Body Check Balls Missing.
9. Axle Pinion Flange Loose.
10. Clutch, band or planetary component damaged. 11. Converter Clutch Faulty. 1. Fluid Level Low. 2. Filter Clogged. 3. Gearshift Linkage Mis-adjusted.
4. Torque Converter Drain Back (Oil drains from torque converter into transmission sump).
5. Rear Band Mis-adjusted. 6. Valve Body Filter Plugged.
7. Oil Pump Gears Worn/Damaged.
8. Governor Circuit and Solenoid Valve Electrical Fault. 9. Hydraulic Pressure Incorrect.
10. Reaction Shaft Seal Rings Worn/Broken. 11. Rear Clutch/Input Shaft, Rear Clutch Seal Rings Damaged. 12. Regulator Valve Stuck. 13. Cooler Plugged.
1. Add Fluid 2. Adjust linkage - setting may be too long. 3. Check engine mount, transmission mount, propeller shaft, rear spring to body bolts, rear control arms, crossmember and axle bolt torque. Tighten loose bolts and replace missing bolts. 4. Remove propeller shaft and replace U-Joint. 5. Check per Service Manual. Correct as needed. 6. Check pressure. Remove, overhaul or adjust valve body as needed. 7. Adjust rear band. 8. Inspect valve body for proper check ball installation. 9. Replace nut and check pinion threads before installing new nut. Replace pinion gear if threads are damaged. 10. Remove, disassemble and repair transmission as necessary. 11. Replace converter. 1. Correct level and check for leaks. 2. Change filter. 3. Adjust linkage and repair linkage if worn or damaged. 4. If vehicle moves normally after 5
seconds after shifting into gear, no repair is necessary. If longer, inspect pump bushing for wear. Replace pump house. 5. Adjust band. 6. Replace fluid and filter. If oil pan and old fluid were full of clutch disc material and/or metal particles, overhaul will be necessary. 7. Remove transmission and replace oil pump. 8. Test with DRBT scan tool and repair as required. 9. Perform pressure test, remove transmission and repair as needed. 10. Remove transmission, remove oil pump and replace seal rings. 11. Remove and disassemble transmission and repair as necessary. 12. Clean. 13. Replace cooler.DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 327
CONDITION NO DRIVE RANGE (REVERSE OK)
NO DRIVE OR REVERSE (VEHICLE WILL NOT MOVE)
POSSIBLE CAUSES
CORRECTION
1. Fluid Level Low.
2. Gearshift Linkage/Cable Loose/Misadjusted. 3. Rear Clutch Burnt.
4. Valve Body Malfunction.
5. Transmission Overrunning Clutch Broken. 6. Input Shaft Seal Rings Worn/ Damaged.
7. Front Planetary Failed Broken. 1. Fluid Level Low.
2. Gearshift Linkage/Cable Loose/Misadjusted. 3. U-Joint/Axle/Transfer Case Broken.
4. Filter Plugged.
5. Oil Pump Damaged.
6. Valve Body Malfunctioned.
7. Transmission Internal Component Damaged.
8. Park Sprag not Releasing - Check Stall Speed, Worn/Damaged/Stuck. 9. Torque Converter Damage.
1. Add fluid and check for leaks if drive is restored. 2. Repair or replace linkage components.
3. Remove and disassemble transmission and rear clutch and seals. Repair/replace worn or damaged parts as needed. 4. Remove and disassemble valve body. Replace assembly if any valves or bores are damaged. 5. Remove and disassemble transmission. Replace overrunning clutch. 6. Remove and disassemble transmission. Replace seal rings and any other worn or damaged parts. 7. Remove and repair. 1. Add fluid and check for leaks if drive is restored. 2. Inspect, adjust and reassemble linkage as needed. Replace worn/damaged parts. 3. Perform preliminary inspection procedure for vehicle that will not move. Refer to procedure in diagnosis section. 4. Remove and disassemble transmission. Repair or replace failed components as needed. Replace filter. If filter and fluid contained clutch material or metal particles, an overhaul may be necessary. Replace cooler as necessary. 5. Perform pressure test to confirm low pressure. Replace pump body assembly if necessary. 6. Check and inspect valve body. Replace valve body (as assembly) if any valve or bore is damaged. Clean and reassemble correctly if all parts are in good condition. 7. Remove and disassemble transmission. Repair or replace failed components as needed. 8. Remove, disassemble, repair.
9. Inspect and replace as required.
21 - 328
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
CONDITION
POSSIBLE CAUSES
CORRECTION
SHIFTS DELAYED OR ERRATIC (SHIFTS ALSO HARSH AT TIMES)
1. Fluid Level Low/High.
2. Fluid Filter Clogged.
3. Throttle Linkage Mis-adjusted.
4. Throttle Linkage Binding.
5. Gearshift Linkage/Cable Mis-adjusted. 6. Clutch or Servo Failure.
7. Governor Circuit Electrical Fault.
8. Front Band Mis-adjusted. 9. Pump Suction Passage Leak.
1. Gearshift Linkage/Cable Mis-adjusted/Damaged. 2. Park Sprag Sticking. 3. Rear Band Mis-adjusted/Worn. 4. Valve Body Malfunction.
5. Rear Servo Malfunction.
6. Direct Clutch in Overdrive Worn.
7. Front Clutch Burnt.
1. Governor Circuit Electrical Fault.
2. Valve Body Malfunction.
3. Front Servo/Kickdown Band Damaged/Burned. 1. Valve Body Malfunction.
NO REVERSE (D RANGES OK)
HAS FIRST/REVERSE ONLY (NO 1-2 OR 2-3
UPSHIFT)MOVES IN 2ND OR 3RD GEAR, ABRUPTLY DOWNSHIFTS TO LOW
1. Correct fluid level and check for leaks if low. 2. Replace filter. If filter and fluid contained clutch material or metal particles, an overhaul may be necessary. 3. Adjust linkage as described in service section. 4. Check cable for binding. Check for return to closed throttle at transmission. 5. Adjust linkage/cable as described in service section. 6. Remove valve body and air test clutch, and band servo operation. Disassemble and repair transmission as needed. 7. Test using DRBT scan tool and repair as required. 8. Adjust band. 9. Check for excessive foam on dipstick after normal driving. Check for loose pump bolts, defective gasket. Replace pump assembly if needed. 1. Repair or replace linkage parts as needed. 2. Replace overdrive annulus gear. 3. Adjust band; replace. 4. Remove and service valve body. Replace valve body if any valves or valve bores are worn or damaged. 5. Remove and disassemble transmission. Replace worn/damaged servo parts as necessary. 6. Disassemble overdrive. Replace worn or damaged parts. 7. Remove and disassemble transmission. Replace worn, damaged clutch parts as required. 1. Test using DRBT scan tool and repair as required. 2. Repair stuck 1-2 shift valve or governor plug. 3. Repair/replace.
1. Remove, clean and inspect. Look for stuck 1-2 valve or governor plug.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 329
CONDITION
POSSIBLE CAUSES
CORRECTION
NO LOW GEAR (MOVES IN 2ND OR 3RD GEAR ONLY)
1. Governor Circuit Electrical Fault.
2. Valve Body Malfunction.
NO KICKDOWN OR NORMAL DOWNSHIFT
3. Front Servo Piston Cocked in Bore. 4. Front Band Linkage Malfunction
1. Throttle Linkage Mis-adjusted. 2. Accelerator Pedal Travel Restricted. 3. Valve Body Hydraulic Pressures Too High or Too Low Due to Valve Body Malfunction or Incorrect Hydraulic Control Pressure Adjustments. 4. Governor Circuit Electrical Fault.
5. Valve Body Malfunction.
6. TPS Malfunction.
7. PCM Malfunction.
8. Valve Body Malfunction.
STUCK IN LOW GEAR (WILL NOT UPSHIFT)
1. Throttle Linkage Mis-adjusted/ Stuck.
2. Gearshift Linkage Mis-adjusted.
3. Governor Component Electrical Fault. 4. Front Band Out of Adjustment. 5. Clutch or Servo Malfunction.
1. Gearshift Linkage Mis-adjusted. 2. Rear Clutch Dragging/Warped. 3. Valve Body Malfunction.
CREEPS IN NEUTRAL
1. Test with DRBT scan tool and repair as required. 2. Remove, clean and inspect. Look for sticking 1-2 shift valve, 2-3 shift valve, governor plug or broken springs. 3. Inspect servo and repair as required.
4. Inspect linkage and look for bind in linkage. 1. Adjust linkage. 2. Verify floor mat is not under pedal, repair worn accelerator cable or bent brackets. 3. Perform hydraulic pressure tests to determine cause and repair as required. Correct valve body pressure adjustments as required.
4. Test with DRBT scan tool and repair as required. 5. Perform hydraulic pressure tests to determine cause and repair as required. Correct valve body pressure adjustments as required. 6. Replace sensor, check with DRBT scan tool. 7. Check with DRBT scan tool and replace if required. 8. Repair sticking 1-2, 2-3 shift valves, governor plugs, 3-4 solenoid, 3-4 shift valve, 3-4 timing valve. 1. Adjust linkage and repair linkage if worn or damaged. Check for binding cable or missing return spring. 2. Adjust linkage and repair linkage if worn or damaged. 3. Check operating pressures and test with DRBT scan tool, repair faulty component. 4. Adjust Band. 5. Air pressure check operation of clutches and bands. Repair faulty component. 1. Adjust linkage. 2. Disassemble and repair. 3. Perform hydraulic pressure test to determine cause and repair as required.
21 - 330
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
CONDITION
BUZZING NOISE
SLIPS IN REVERSE ONLY
SLIPS IN FORWARD DRIVE RANGES
SLIPS IN LOW GEAR 9D9
ONLY, BUT NOT IN MANUAL 1 POSITIONPOSSIBLE CAUSES
1. Fluid Level Low 2. Shift Cable Mis-assembled.
3. Valve Body Mis-assembled.
4. Pump Passages Leaking.
5. Cooling System Cooler Plugged. 6. Overrunning Clutch Damaged. 1. Fluid Level Low. 2. Gearshift Linkage Mis-adjusted. 3. Rear Band Mis-adjusted. 4. Rear Band Worn. 5. Overdrive Direct Clutch Worn.
6. Hydraulic Pressure Too Low.
7. Rear Servo Leaking.
8. Band Linkage Binding. 1. Fluid Level Low. 2. Fluid Foaming.
3. Throttle Linkage Mis-adjusted. 4. Gearshift Linkage Mis-adjusted. 5. Rear Clutch Worn. 6. Low Hydraulic Pressure Due to Worn Pump, Incorrect Control Pressure Adjustments, Valve Body Warpage or Malfunction, Sticking, Leaking Seal Rings, Clutch Seals Leaking, Servo Leaks, Clogged Filter or Cooler Lines. 7. Rear Clutch Malfunction, Leaking Seals or Worn Plates. 8. Overrunning Clutch Worn, Not Holding (Slips in 1 Only). Overrunning Clutch Faulty.
CORRECTION
1. Add fluid and check for leaks. 2. Route cable away from engine and bell housing. 3. Remove, disassemble, inspect valve body. Reassemble correctly if necessary. Replace assembly if valves or springs are damaged. Check for loose bolts or screws. 4. Check pump for porous casting, scores on mating surfaces and excess rotor clearance. Repair as required. Loose pump bolts. 5. Replace cooler. 6. Replace clutch. 1. Add fluid and check for leaks. 2. Adjust linkage. 3. Adjust band. 4. Replace as required. 5. Disassemble overdrive. Repair as needed. 6. Perform hydraulic pressure tests to determine cause. 7. Air pressure check clutch-servo operation and repair as required. 8. Inspect and repair as required. 1. Add fluid and check for leaks. 2. Check for high oil level, bad pump gasket or seals, dirt between pump halves and loose pump bolts. Replace pump if necessary. 3. Adjust linkage. 4. Adjust linkage. 5. Inspect and replace as needed. 6. Perform hydraulic and air pressure tests to determine cause.
7. Air pressure check clutch-servo operation and repair as required. 8. Replace Clutch.
Replace overrunning clutch.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 331
CONDITION
POSSIBLE CAUSES
CORRECTION
GROWLING, GRATING OR SCRAPING NOISES
DRAGS OR LOCKS UP
1. Drive Plate Broken. 2. Torque Converter Bolts Hitting Dust Shield. 3. Planetary Gear Set Broken/ Seized. 4. Overrunning Clutch Worn/Broken.
5. Oil Pump Components Scored/ Binding. 6. Output Shaft Bearing or Bushing Damaged. 7. Clutch Operation Faulty.
8. Front and Rear Bands Mis- adjusted. 1. Fluid Level Low. 2. Clutch Dragging/Failed
3. Front or Rear Band Mis-adjusted. 4. Case Leaks Internally.
5. Servo Band or Linkage Malfunction. 6. Overrunning Clutch Worn.
7. Planetary Gears Broken.
8. Converter Clutch Dragging.
NO 4-3 DOWNSHIFT
1. Circuit Wiring and/or Connectors Shorted.
2. PCM Malfunction.
3. TPS Malfunction 4. Lockup Solenoid Not Venting.
5. Overdrive Solenoid Not Venting.
6. Valve Body Valve Sticking.
1. Replace. 2. Dust shield bent. Replace or repair.
3. Check for debris in oil pan and repair as required. 4. Inspect and check for debris in oil pan. Repair as required. 5. Remove, inspect and repair as required.
6. Remove, inspect and repair as required.
7. Perform air pressure check and repair as required. 8. Adjust bands.
1. Check and adjust level. 2. Air pressure check clutch operation and repair as required. 3. Adjust bands. 4. Check for leakage between passages in case. 5. Air pressure check servo operation and repair as required. 6. Remove and inspect clutch. Repair as required. 7. Remove, inspect and repair as required (look for debris in oil pan). 8. Check for plugged cooler. Inspect pump for excessive side clearance. Replace pump as required. 1. Test wiring and connectors with test lamp and volt/ohmmeter. Repair wiring as necessary. Replace connectors and/or harnesses as required. 2. Check PCM operation with DRBT scan tool. Replace PCM only if faulty. 3. Check TPS with DRBT scan tool at PCM. 4. Remove valve body and replace solenoid assembly if plugged or shorted. 5. Remove valve body and replace solenoid if plugged or shorted. 6. Repair stuck 3-4 shift valve or lockup timing valve.
21 - 332
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
CONDITION NO 4-3 DOWNSHIFT WHEN CONTROL SWITCH IS TURNED OFF
POSSIBLE CAUSES
1. Control Switch Open/Shorted. 2. Overdrive Solenoid Connector Shorted. 3. PCM Malfunction.
4. Valve Body Stuck Valves.
CLUNK NOISE FROM DRIVELINE ON CLOSED THROTTLE 4-3
DOWNSHIFT3-4 UPSHIFT OCCURS IMMEDIATELY AFTER 2-3
SHIFT1. Transmission Fluid Low. 2. Throttle Cable Mis-adjusted. 3. Overdrive Clutch Select Spacer Wrong Spacer. 1. Overdrive Solenoid Connector or Wiring Shorted.
2. TPS Malfunction.
3. PCM Malfunction.
4. Overdrive Solenoid Malfunction. 5. Valve Body Malfunction.
WHINE/NOISE RELATED TO ENGINE SPEED
1. Fluid Level Low. 2. Shift Cable Incorrect Routing.
DR
CORRECTION
1. Test and replace switch if faulty. 2. Test solenoids and replace if seized or shorted. 3. Test with DRBT scan tool. Replace PCM if faulty. 4. Repair stuck 3-4, lockup or lockup timing valve. 1. Add Fluid. 2. Adjust cable. 3. Replace overdrive piston thrust plate spacer. 1. Test connector and wiring for loose connections, shorts or ground and repair as needed. 2. Test TPS and replace as necessary. Check with DRBT scan tool. 3. Test PCM with DRBT scan tool and replace controller if faulty. 4. Replace solenoid. 5. Remove, disassemble, clean and inspect valve body components. Make sure all valves and plugs slide freely in bores. Polish valves with crocus cloth if needed. 1. Add fluid and check for leaks. 2. Check shift cable for correct routing. Should not touch engine or bell housing.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 333
CONDITION
NO 3-4 UPSHIFT
POSSIBLE CAUSES
1. O/D Switch In OFF Position. 2. Overdrive Circuit Fuse Blown.
3. O/D Switch Wire Shorted/Open Cut.
4. Distance or Coolant Sensor Malfunction. 5. TPS Malfunction.
6. Neutral Sense to PCM Wire Shorted/Cut.
7. PCM Malfunction.
8. Overdrive Solenoid Shorted/Open.
9. Solenoid Feed Orifice in Valve Body Blocked. 10. Overdrive Clutch Failed.
11. Hydraulic Pressure Low.
12. Valve Body Valve Stuck.
13. O/D Piston Incorrect Spacer.
14. Overdrive Piston Seal Failure. 15. O/D Check Valve/Orifice Failed.
CORRECTION
