Login- Download PDF Manual
-
metallic or fiber contamination in the fluid, replace the torque converter. Fluid contamination and trans- mission failure can result if not done.
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 353
BAND ADJUSTMENT AND FINAL
(1) Adjust front and rear bands as follows:
(a) Loosen locknut on each band adjusting screw
(b) Tighten both adjusting screws to 8 N·m (72
(c) Back off
front band adjusting screw 1-3/4
4-5 turns.
in. lbs.).
turns.
(d) Back off rear band adjusting screw 3 turns. (e) Hold each adjusting screw in position and
tighten locknut to 34 N·m (25 ft. lbs.) torque. (2) Install magnet in oil pan. Magnet seats on
small protrusion at corner of pan.
(3) Position new oil pan gasket on case and install oil pan. Tighten pan bolts to 13.6 N·m (125 in. lbs.). (4) Install throttle valve and shift selector levers
on valve body manual lever shaft.
(5) Apply small quantity of dielectric grease to ter- minal pins of solenoid case connector and neutral switch.
(6) Fill transmission with recommended fluid.
INSTALLATION
(1) Check torque converter hub inner and outer diameters and hub drive notches for sharp edges burrs, scratches, or nicks. Polish the hub and notches with 320/400 grit paper and crocus cloth if necessary. The hub must be smooth to avoid damaging pump seal at installation.
(2) Lubricate pocket in the rear oil pump seal lip
with transmission fluid.
(3) Lubricate converter pilot hub of the crankshaft
with a light coating of Mopart High Temp Grease.
(4) Align and install converter in oil pump. (5) Carefully insert converter in oil pump. Then rotate converter back and forth until fully seated in pump gears.
(6) Check converter seating with steel scale and straightedge (Fig. 65). Surface of converter lugs should be 19mm (0.75 in.) to rear of straightedge when converter is fully seated.
(7) Temporarily secure converter with C-clamp. (8) Position transmission on jack and secure it
with chains. (9) Check
of
condition
driveplate. Replace the plate if cracked, distorted or damaged. Also be sure transmission dowel pins are seated in engine block and protrude far enough to hold transmission in alignment.
converter
(10) Raise transmission and align converter with drive plate and converter housing with engine block. (11) Move transmission forward. Then raise, lower or tilt transmission to align converter housing with engine block dowels.
Fig.62InstalltheTransmissionRangeSensor
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET 3 - TRANSMISSION RANGE SENSOR
Fig.63AccumulatorPistonAndSprings
1 - ACCUMULATOR PISTON 2 - OUTER SPRING 3 - INNER SPRING
Fig.64ManualLeverShaftSeal
1 - 15/1688 SOCKET 2 - SEAL
(10) Install torque converter. Use C-clamp or metal
strap to hold converter in place for installation.
21 - 354
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
Fig.65CheckingConverterSeating-Typical
1 - SCALE 2 - STRAIGHTEDGE
Fig.66GearshiftCableAtTransmission
1 - GEARSHIFT CABLE 2 - TRANSMISSION MANUAL LEVER 3 - CABLE SUPPORT BRACKET
(12) Carefully work transmission forward and over engine block dowels until converter hub is seated in crankshaft.
(13) Install bolts attaching converter housing to
engine.
(14) Install rear support. (15) Install the rear transmission crossmember. (16) Lower transmission onto crossmember and install bolts attaching transmission mount to cross- member.
(17) Remove engine support fixture. (18) Install the transfer case, if equipped. (19) Install crankshaft position sensor. (Refer to 14
- FUEL SYSTEM/FUEL INJECTION/CRANKSHAFT POSITION SENSOR - INSTALLATION)(20) Connect gearshift cable (Fig. 66) and throttle
cable to transmission.
CAUTION: It is essential that correct length bolts be used to attach the converter to the driveplate. Bolts that are too long will damage the clutch surface inside the converter.
(22) Install torque converter-to-driveplate bolts. (23) Install converter housing access cover. (24) Install starter motor and cooler line bracket. (Refer to 8 - ELECTRICAL/STARTING/STARTER MOTOR - INSTALLATION)
(25) Connect cooler lines (Fig. 67) to transmission. (26) Install transmission fill tube. Install new seal
on tube before installation.
(21) Connect wires to the transmission range sen- sor and transmission solenoid connector. Be sure the transmission harnesses are properly routed.
removed.
Fig.67TransmissionCoolerLines
1 - TRANSMISSION 2 - RADIATOR 3 - COOLER LINES
(27) Install any exhaust components previously
(28) Align and connect propeller shaft. (Refer to 3 - DRIVELINE/PROPELLER
DIFFERENTIAL SHAFT/PROPELLER SHAFT - INSTALLATION)
(29) Adjust gearshift
cable and throttle valve
cable, if necessary. the
(30) Install
equipped.
transfer
case
skid plate,
if
(31) Lower vehicle. (32) Fill transmission with Mopart ATF +4, Auto-
matic Transmission fluid.
DR AUTOMATIC TRANSMISSION - 48RE (Continued) SCHEMATICS AND DIAGRAMS
AUTOMATIC TRANSMISSION - 48RE
21 - 355
HYDRAULIC SCHEMATICS
21 - 356
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 357
21 - 358
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 359
21 - 360
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 361
21 - 362
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 363
21 - 364
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 365
21 - 366
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 367
DR
GEAR RATIOS
1ST GEAR 2ND GEAR 3RD GEAR 4TH GEAR REVERSE
2.45:1
1.45:1
1.00:1
0.69:1
2.21:1AUTOMATIC TRANSMISSION - 48RE
21 - 368
AUTOMATIC TRANSMISSION - 48RE (Continued) SPECIFICATIONSTRANSMISSION
GENERAL
Component
Metric
Inch
Planetary end play
0.150-1.22
0.006-0.048
mm
in.
Input shaft end play
0.86-2.13
0.034-0.084
Clutch pack clearance/
Front.
mm
2.5-4.09
mm
in.
0.098-0.161
in.
Clutch pack clearance/
0.635-0.914
0.025-0.036
Rear.
Front clutch Rear clutch
mm
in.
5 discs 4 discs
Overdrive clutch
Direct clutch
5(STD) or 6 (HO) discs 23 single sided discs
Band adjustment from
72 in. lbs. Front band Rear band
Back off 1 3/4 turns
Back off 3 turns
Recommended fluid
MoparT ATF +4, Automatic
Transmission Fluid
THRUST WASHER/SPACER/SNAP-RING DIMENSIONS
Component
Front clutch thrust washer (reaction shaft support
hub)
Rear clutch thrust washer (clutch retainer)
Intermediate shaft thrust plate (shaft hub pilot) Output shaft thrust washer (rear clutch hub)
Rear clutch pack snap-ring
Planetary geartrain snap-ring (at front of output
shaft)
Metric 1.55 mm
2.15 mm 2.59 mm 1.55 mm
1.5-1.6 mm 1.3-1.4 mm
1.75-1.8 mm 2.1-2.2 mm 1.5-1.6 mm
1.9-1.95 mm 1.4-1.5 mm
1.6-1.7 mm
Inch
0.061 in.
0.084 in. 0.102 in. 0.061 in.
0.060-0.063 in. 0.052-0.054 in.
0.068-0.070 in. 0.083-0.085 in. 0.060-0.062 in.
0.074-0.076 in. 0.055-0.059 in.
0.062-0.066 in.
Overdrive piston thrust plate
Intermediate shaft spacer
Thrust plate and spacer are select
fit. Refer to size charts and
selection procedures in Overdrive
Unit D&A procedures
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 369
TORQUE SPECIFICATIONS
DESCRIPTION
Fitting, cooler line at trans
Bolt, torque convertor Bolt, clevis bracket to
crossmember
Bolt, clevis bracket to rear
support
Bolt, driveplate to
crankshaft
Plug, front band reaction Locknut, front band adj.
Bolt, fluid pan
Screws, fluid filter
Bolt, oil pump
Bolt, overrunning clutch
cam
Bolt, O/D to trans.
Bolt, O/D piston retainer Plug, pressure test port
Bolt, reaction shaft
support
Locknut, rear band
Bolt, valve body to case
Sensor, trans speed Screw, solenoid wiring
connector
Screw, solenoid to transfer
plate
Bracket, transmission range sensor mounting
Screw, transmission range
sensor to mounting
bracket
N·m 18
31
4768
75
17
34
17
20
1734
17
14
2041
12
2734
3.4
Ft. Lbs.
13
3550
55
13
25
13
15
1325
13
10
1530
20In. Lbs.
270
35
100
35
35
300
30
AUTOMATIC TRANSMISSION - 48RE
21 - 370
AUTOMATIC TRANSMISSION - 48RE (Continued) SPECIAL TOOLSRE TRANSMISSION
DR
Adapter,BandAdjuster-C-3705
Studs,OilPumpPilot-C-3288-B
Gauge,Pressure-C-3292
Gauge,Pressure-C-3293SP
Stand,TransmissionRepair-C-3750-B
Puller,SlideHammer-C-3752
Set,DialIndicator-C-3339
Gauge,ThrottleSetting-C-3763
Compressor,Spring-C-3422-B
Installer,Seal-C-3860-A
DR AUTOMATIC TRANSMISSION - 48RE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 371
Compressor,Spring-C-3863-A
Remover/Installer,Bushing-C-4470
Remover,Seal-C-3985-B
DialCaliper-C-4962
Installer,Seal-C-3995-A
SpringCompressorandAlignmentShaft-6227
Handle,Universal-C-4171
Bar,Gauge-6311
Gauge,Block-6312
21 - 372
AUTOMATIC TRANSMISSION - 48RE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
ACCUMULATOR DESCRIPTION
The accumulator (Fig. 68) is a hydraulic device that has the sole purpose of cushioning the applica- tion of a band or clutch. The accumulator consists of a dual-land piston and a spring located in a bore in the transmission case. The 3-4 accumulator is located in a housing attached to the side of the valve body (Fig. 69).
Fig.68Accumulator
1 - ACCUMULATOR PISTON 2 - PISTON SPRING
Retainer,DetentBallandSpring-6583
Installer,OverdrivePistonSeal-8114
Socket,TRSMountingBracket-8581
Installer,Seal-9037
Fig.693-4AccumulatorandHousing
1 - ACCUMULATOR PISTON 2 - 3-4 ACCUMULATOR HOUSING 3 - TEFLON SEALS 4 - PISTON SPRING 5 - COVER PLATE AND SCREWS
DR ACCUMULATOR (Continued) OPERATION
Both the accumulator and the 3-4 accumulator function the same. Line pressure is directed to the small end of the piston when the transmission is placed into a DRIVE position (Fig. 70), bottoming it against the accumulator plate. When the 1-2 upshift occurs (Fig. 71), line pressure is directed to the large end of the piston and then to the kickdown servo. As the line pressure reaches the accumulator, the com- bination of spring pressure and line pressure forces the piston away from the accumulator plate. This causes a balanced pressure situation, which results in a cushioned band application. After the kickdown servo has become immovable, line pressure will fin- ish pushing the accumulator up into its bore. When the large end of the accumulator piston is seated in its bore, the band or clutch is fully applied.
NOTE: The accumulator is shown in the inverted position for illustrative purposes.
Fig.70AccumulatorinDRIVE-FIRSTGearPosition 1 - LINE PRESSURE
AUTOMATIC TRANSMISSION - 48RE
21 - 373
Fig.71AccumulatorinSECONDGearPosition
1 - BOTTOM OF BORE 2 - LINE PRESSURE 3 - SHUTTLE VALVE
INSPECTION
Inspect the accumulator piston and seal rings. Replace the seal rings if worn or cut. Replace the pis- ton if chipped or cracked.
Check condition of the accumulator spring. Replace the spring if the coils are cracked, distorted or col- lapsed.
BANDS DESCRIPTION
KICKDOWN (FRONT) BAND
The kickdown, or “front”, band (Fig. 72) holds the common sun gear of the planetary gear sets. The front (kickdown) band is made of steel, and faced on its inner circumference with a friction-type lining. One end of the band is anchored to the transmission case, and the other is acted on with a pushing force by a servo piston. The front band is a single-wrap design (the band does not completely encompass/ wrap the drum that it holds).
21 - 374
BANDS (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
front clutch retainer, which is splined to the sun gear driving shell, and in turn splined directly to the sun gear. The application of the band by the servo is typ- ically done by an apply lever and link bar.
LOW/REVERSE (REAR) BAND
The rear band holds the rear planet carrier sta- tionary by being mounted around and applied to the low/reverse drum.
ADJUSTMENTS
ADJUSTMENT - BANDS
Fig.72FrontBand
1 - FRONT BAND 2 - TRANSMISSION HOUSING
LOW/REVERSE (REAR) BAND
The low/reverse band, or “rear”, band (Fig. 73) is sim- ilar in appearance and operation to the front band. The rear band is slightly different in that it does not use a link bar, but is acted directly on by the apply lever. This is referred to as a double-wrap band design (the drum is completely encompassed/wrapped by the band). The double-wrap band provides a greater holding power in comparison to the single-wrap design.
FRONT BAND The front
(kickdown) band adjusting screw is located on the left side of the transmission case above the manual valve and throttle valve levers.
(1) Raise vehicle. (2) Loosen band adjusting screw locknut (Fig. 74). Then back locknut off 3-5 turns. Be sure adjusting screw turns freely in case. Apply lubricant to screw threads if necessary.
(3) Tighten band adjusting screw to 8 N·m (72 in. lbs.) torque with Inch Pound Torque Wrench C-3380-A, a 3-in. extension and an appropriate Torx™ socket.
CAUTION: If Adapter C-3705 is needed to reach the adjusting screw, tighten the screw to only 5 N·m (47-50 in. lbs.) torque.
(4) Back off front band adjusting screw 1-3/4 turns. (5) Hold adjuster screw in position and tighten
locknut to 41 N·m (30 ft. lbs.) torque.
(6) Lower vehicle.
Fig.73RearBand
1 - ADJUSTING SCREW 2 - LOCKNUT 3 - LEVER 4 - REAR BAND 5 - REACTION PIN 6 - O-RINGS 7 - PIVOT PIN
OPERATION
KICKDOWN (FRONT) BAND
The kickdown band holds the common sun gear of the planetary gear sets by applying and holding the
Fig.74FrontBandAdjustmentScrewLocation
1 - LOCK-NUT 2 - FRONT BAND ADJUSTER
DR BANDS (Continued) REAR BAND
AUTOMATIC TRANSMISSION - 48RE
21 - 375
The transmission oil pan must be removed for
access to the rear band adjusting screw.
(1) Raise vehicle. (2) Remove transmission oil pan and drain fluid. (3) Loosen band adjusting screw locknut 5-6 turns.
Be sure adjusting screw turns freely in lever.
(4) Tighten adjusting screw to 8 N·m (72 in. lbs.)
torque (Fig. 75).
(5) Back off adjusting screw 3 turns. (6) Hold adjusting screw in place and tighten lock-
nut to 34 N·m (25 ft. lbs.) torque.
(7) Position new gasket on oil pan and install pan on transmission. Tighten pan bolts to 17 N·m (13 ft. lbs.) torque.
(8) Lower vehicle and refill
transmission with
Mopart ATF +4, Automatic Transmission fluid.
Fig.75RearBandAdjustmentScrewLocation
1 - LOW-REVERSE BAND ADJUSTMENT
BRAKE TRANSMISSION SHIFT INTERLOCK SYSTEM DESCRIPTION
The Brake Transmission Shifter Interlock (BTSI) (Fig. 76), is a solenoid operated system. It consists of a solenoid permanently mounted on the gearshift cable.
OPERATION
The system locks the shifter into the PARK posi- tion. The interlock system is engaged whenever the ignition switch is in the LOCK or ACCESSORY posi- tion. An additional electrically activated feature will prevent shifting out of the PARK position unless the brake pedal is depressed approximately one-half an inch. A magnetic holding device in line with the park lock cable is energized when the ignition is in the RUN position. When the key is in the RUN position is depressed, the shifter is and the brake pedal
Fig.76BrakeTransmissionInterlockMechanism 1 - STEERING COLUMN 2 - GEARSHIFT CABLE 3 - GEARSHIFT CABLE LOCK TAB 4 - BTSI SOLENOID LOCK TAB 5 - BTSI CONNECTOR
unlocked and will move into any position. The inter- lock system also prevents the ignition switch from being turned to the LOCK or ACCESSORY position, unless the shifter is fully locked into the PARK posi- tion.
DIAGNOSIS AND TESTING - BRAKE TRANSMISSION SHIFT INTERLOCK
(1) Verify that the key can only be removed in the
PARK position
(2) When the shift lever is in PARK And the shift handle pushbutton is in the “OUT” position, the igni- tion key cylinder should rotate freely from OFF to LOCK. When the shifter is in any other gear or neu- tral position, the ignition key cylinder should not rotate to the LOCK position.
(3) Shifting out of PARK should not be possible when the ignition key cylinder is in the OFF posi- tion.
(4) Shifting out of PARK should not be possible while applying normal pushbutton force and ignition key cylinder is in the RUN or START positions unless the foot brake pedal is depressed approxi- mately 1/2 inch (12mm).
(5) Shifting out of PARK should not be possible when the ignition key cylinder is in the ACCESSORY or LOCK positions.
(6) Shifting between any gears, NEUTRAL or into PARK may be done without depressing foot brake pedal with ignition switch in RUN or START posi- tions.
AUTOMATIC TRANSMISSION - 48RE
21 - 376
BRAKE TRANSMISSION SHIFT INTERLOCK SYSTEM (Continued) ADJUSTMENTS - BRAKE TRANSMISSION SHIFT INTERLOCKDR
Correct cable adjustment is important to proper interlock operation. The gearshift cable must be cor- rectly adjusted in order to shift out of PARK.
ADJUSTMENT PROCEDURE
(1) Remove the steering column trim as necessary for access to the brake transmission shift interlock. (2) Shift the transmission into the PARK position. (3) Pull upward on both the BTSI lock tab and the
gearshift cable lock tab (Fig. 77).
(4) Verify that the shift lever is in the PARK posi-
tion.
(5) Verify positive engagement of the transmission park lock by attempting to rotate the propeller shaft. The shaft will not rotate when the park lock is engaged.
(6) Turn ignition switch to LOCK position. Be sure ignition key cylinder is in the LOCK posi- tion. Cable will not adjust correctly in any other position.
(7) Ensure that the cable is free to self-adjust by
pushing cable rearward and releasing.
(8) Push the gearshift cable lock tab down until it
snaps in place.
(11) Push the BTSI lock tab down until it snaps
into place and remove the drill bit.
(12) Install any steering column trim previously
removed.
BTSI FUNCTION CHECK
position only.
(1) Verify removal of ignition key allowed in PARK
(2) When the shift lever is in PARK, the ignition key cylinder should rotate freely from off to lock. When the shifter is in any other position, the ignition key should not rotate from off to lock.
(3) Shifting out of PARK should be possible when
the ignition key cylinder is in the off position.
(4) Shifting out of PARK should not be possible while applying normal force, and ignition key cylinder is in the run or start positions, unless the foot brake pedal is depressed approximately 1/2 inch (12mm).
(5) Shifting out of PARK should not be possible when the ignition key cylinder is in the accessory or lock position.
(6) Shifting between any gear and NEUTRAL, or PARK, may be done without depressing foot brake with ignition switch in run or start positions.
(7) Engine starts must be possible with shifter lever in PARK or NEUTRAL positions only. Engine starts must not be possible in any position other than PARK or NEUTRAL.
(8) With shifter lever in the: † PARK position - Apply upward force on the shift arm and remove pressure. Engine starts must be possible. † PARK position - Apply downward force on the shift arm and remove pressure. Engine starts must be possible. † NEUTRAL position - Normal position. Engine † NEUTRAL position - Engine running and brakes applied, apply upward force on the shift arm. Trans- mission shall not be able to shift from neutral to reverse.
starts must be possible.
Fig.77BrakeTransmissionInterlockMechanism 1 - STEERING COLUMN 2 - GEARSHIFT CABLE 3 - GEARSHIFT CABLE LOCK TAB 4 - BTSI SOLENOID LOCK TAB 5 - BTSI CONNECTOR
(9) Locate the BTSI alignment hole in the bottom of the BTSI mechanism between the BTSI lock tab and the BTSI connector.
(10) Move the BTSI assembly up or down on the gearshift cable until an appropriate size drill bit can be inserted into the alignment hole and through the assembly.
ELECTRONIC GOVERNOR DESCRIPTION
ponents used for governor pressure control include:
Governor pressure is controlled electronically. Com- † Governor body † Valve body transfer plate † Governor pressure solenoid valve † Governor pressure sensor † Fluid temperature thermistor † Throttle position sensor (TPS) † Transmission speed sensor † Powertrain control module (PCM)
DR ELECTRONIC GOVERNOR (Continued) GOVERNOR PRESSURE SOLENOID VALVE
The solenoid valve is a duty-cycle solenoid which regulates the governor pressure needed for upshifts and downshifts. It is an electro-hydraulic device located in the governor body on the valve body trans- fer plate (Fig. 78).
AUTOMATIC TRANSMISSION - 48RE
21 - 377
governor pressure for varying conditions. One curve is used for operation when fluid temperature is at, or below, –1°C (30°F). A second curve is used when fluid temperature is at, or above, 10°C (50°F) during nor- mal city or highway driving. A third curve is used during wide-open throttle operation. The fourth curve is used when driving with the transfer case in low range.
OPERATION
Fig.78GovernorPressureSolenoidValve
1 - SOLENOID FILTER 2 - GOVERNOR PRESSURE SOLENOID
GOVERNOR PRESSURE SENSOR
The governor pressure sensor measures output pressure of the governor pressure solenoid valve (Fig. 79).
Fig.79GovernorPressureSensor
1 - GOVERNOR BODY 2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID TEMPERATURE THERMISTOR
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate is designed to supply transmis- sion line pressure to the governor pressure solenoid valve and to return governor pressure.
The governor pressure solenoid valve is mounted in the governor body. The body is bolted to the lower side of the transfer plate (Fig. 79).
GOVERNOR PRESSURE CURVES
There are four governor pressure curves pro- grammed into the transmission control module. The different curves allow the control module to adjust
Compensation is required for performance varia- tions of two of the input devices. Though the slope of the transfer functions is tightly controlled, offset may vary due to various environmental factors or manu- facturing tolerances.
The pressure transducer is affected by barometric pressure as well as temperature. Calibration of the zero pressure offset is required to compensate for shifting output due to these factors.
Normal calibration will be performed when sump temperature is above 50 degrees F, or in the absence of sump temperature data, after the first 10 minutes of vehicle operation. Calibration of the pressure transducer offset occurs each time the output shaft speed falls below 200 RPM. Calibration shall be repeated each 3 seconds the output shaft speed is below 200 RPM. A 0.5 second pulse of 95% duty cycle is applied to the governor pressure solenoid valve and the transducer output is read during this pulse. Averaging of the transducer signal is necessary to reject electrical noise.
Under cold conditions (below 50 degrees F sump), the governor pressure solenoid valve response may be too slow to guarantee 0 psi during the 0.5 second calibration pulse. Calibration pulses are continued during this period, however the transducer output valves are discarded. Transducer offset must be read at key-on, under conditions which promote a stable reading. This value is retained and becomes the off- set during the 9cold9 period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to normal transmission line pressure. The outlet side of the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to produce governor pressure. The average current supplied to the solenoid controls governor pressure. One amp current produces zero kPa/psi governor pressure. Zero amps sets the maximum governor pressure.
The powertrain control module (PCM) turns on the trans control relay which supplies electrical power to the solenoid valve. Operating voltage is 12 volts (DC). The PCM controls the ground side of the sole- noid using the governor pressure solenoid control cir- cuit.
AUTOMATIC TRANSMISSION - 48RE
21 - 378
ELECTRONIC GOVERNOR (Continued) GOVERNOR PRESSURE SENSORThe sensor output signal provides the necessary feedback to the PCM. This feedback is needed to ade- quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the solenoid valve through the governor body. It also channels governor pressure from the solenoid valve to the governor circuit. It is the solenoid valve that develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven- tional governor can delay shifts, resulting in higher than normal shift speeds and harsh shifts. The elec- tronically controlled low temperature governor pres- sure curve is higher than normal to make the transmission shift at normal speeds and sooner. The PCM uses a temperature sensor in the transmission oil sump to determine when low temperature gover- nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased computing power of the PCM and through access to data on engine operating conditions provided by the PCM that were not available with the previous stand-alone electronic module. This facilitated the development of a load adaptive shift strategy - the ability to alter the shift schedule in response to vehi- cle load condition. One manifestation of this capabil- ity is grade 9hunting9 prevention - the ability of the transmission logic to delay an upshift on a grade if the engine does not have sufficient power to main- tain speed in the higher gear. The 3-2 downshift and the potential for hunting between gears occurs with a heavily loaded vehicle or on steep grades. When hunting occurs, it is very objectionable because shifts are frequent and accompanied by large changes in noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem- ory in the PCM assures that up-shifts occur at the preprogrammed optimum speed. WOT operation is determined from the throttle position sensor, which is also a part of the emission control system. The ini-
DR
tial setting for the WOT upshift is below the opti- mum engine speed. As WOT shifts are repeated, the PCM learns the time required to complete the shifts by comparing the engine speed when the shifts occur to the optimum speed. After each shift, the PCM adjusts the shift point until the optimum speed is reached. The PCM also considers vehicle loading, grade and engine performance changes due to high altitude in determining when to make WOT shifts. It does this by measuring vehicle and engine accelera- tion and then factoring in the shift time.
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low range, the engine can accelerate to its peak more rapidly than in Normal range, resulting in delayed shifts and undesirable engine 9flare.9 The low range governor pressure curve is also higher than normal to initiate upshifts sooner. The PCM compares elec- tronic vehicle speed signal used by the speedometer to the transmission output shaft speed signal to determine when the transfer case is in low range.
REMOVAL
(1) Hoist and support vehicle on safety stands. (2) Remove transmission fluid pan and filter. (3) Disengage wire connectors from pressure sen-
sor and solenoid (Fig. 80).
Fig.80GovernorSolenoidAndPressureSensor
1 - PRESSURE SENSOR 2 - PRESSURE SOLENOID 3 - GOVERNOR
DR ELECTRONIC GOVERNOR (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 379
(4) Remove
screws holding pressure
solenoid
(9) Separate governor body from valve body (Fig.
retainer to governor body.
83).
(5) Separate solenoid retainer from governor (Fig.
(10) Remove governor body gasket.
81).
Fig.81PressureSolenoidRetainer
1 - PRESSURE SOLENOID RETAINER 2 - GOVERNOR
(6) Pull solenoid from governor body (Fig. 82). (7) Pull pressure sensor from governor body. (8) Remove bolts holding governor body to valve
body.
Fig.83GovernorBodyandGasket
1 - GOVERNOR BODY 2 - GASKET
INSTALLATION
Before installing the pressure sensor and solenoid in the governor body, replace o-ring seals, clean the gasket surfaces and replace gasket.
(1) Place gasket in position on back of governor
body (Fig. 84).
body.
(2) Place governor body in position on valve body. (3) Install bolts to hold governor body to valve
Fig.82PressureSolenoidandO-ring
1 - PRESSURE SOLENOID 2 - O-RING 3 - GOVERNOR
Fig.84GovernorBodyandGasket
1 - GOVERNOR BODY 2 - GASKET
21 - 380
ELECTRONIC GOVERNOR (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(4) Lubricate o-ring on pressure sensor with trans-
mission fluid.
(5) Align pressure sensor to bore in governor body. (6) Push pressure sensor into governor body. (7) Lubricate o-ring, on pressure solenoid, with
transmission fluid.
body (Fig. 85).
(8) Align pressure solenoid to bore in governor
(9) Push solenoid into governor body.
Fig.85PressureSolenoidandO-ring
1 - PRESSURE SOLENOID 2 - O-RING 3 - GOVERNOR
(10) Place solenoid retainer in position on governor
slide hammer.
(Fig. 86).
(11) Install
screws
to hold pressure
retainer to governor body.
solenoid
INSTALLATION
(14) Lower vehicle and road test to verify repair.
Fig.87GovernorSolenoidAndPressureSensor
1 - PRESSURE SENSOR 2 - PRESSURE SOLENOID 3 - GOVERNOR
EXTENSION HOUSING SEAL REMOVAL
(1) Raise vehicle. (2) Mark propeller shaft and axle yoke for align-
ment reference.
(3) Disconnect and remove propeller shaft. (4) Remove old seal with a screw mounted in a
(1) Place seal in position on overdrive housing. (2) Drive seal
into overdrive housing with Seal
Installer 9037 (Fig. 88).
(3) Carefully guide propeller shaft slip yoke into housing and onto output shaft splines. Align marks made at removal and connect propeller shaft to rear axle pinion yoke.
Fig.86PressureSolenoidRetainer
1 - PRESSURE SOLENOID RETAINER 2 - GOVERNOR
Fig.88InstallingOverdriveHousingYokeSeal
1 - SPECIAL TOOL 9037
2 - SPECIAL TOOL C-4171(12) Engage wire connectors into pressure sensor
and solenoid (Fig. 87).
(13) Install transmission fluid pan and (new) filter.
DR
AUTOMATIC TRANSMISSION - 48RE
21 - 381
FLUID AND FILTER
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air along with the fluid. Air in the fluid will cause fluid pressures to be low and develop slower than normal. If the transmission is overfilled, the gears churn the fluid into foam. This aerates the fluid and causing the same conditions occurring with a low level. In either case, air bubbles cause fluid overheating, oxi- dation and varnish buildup which interferes with valve and clutch operation. Foaming also causes fluid expansion which can result in fluid overflow from the transmission vent or fill tube. Fluid overflow can eas- ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has two primary causes.
(1) A result of restricted fluid flow through the main and/or auxiliary cooler. This condition is usu- ally the result of a faulty or improperly installed drainback valve, a damaged main cooler, or severe restrictions in the coolers and lines caused by debris or kinked lines.
(2) Heavy duty operation with a vehicle not prop- erly equipped for this type of operation. Trailer tow- ing or similar high load operation will overheat the transmission fluid if improperly equipped. Such vehicles should have an auxiliary transmission fluid cooler, a heavy duty cooling sys- tem, and the engine/axle ratio combination needed to handle heavy loads.
the vehicle is
DIAGNOSIS AND TESTING - FLUID CONTAMINATION
result of:
checking level
Transmission fluid contamination is generally a † adding incorrect fluid † failure to clean dipstick and fill tube when † engine coolant entering the fluid † internal failure that generates debris † overheat that generates sludge (fluid break- down)† failure to replace contaminated converter after repair The use of non-recommended fluids can result in transmission failure. The usual results are erratic shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped clean before checking fluid level. Dirt, grease and other foreign material on the cap and tube could fall into the tube if not removed beforehand. Take the time to wipe the cap and tube clean before withdraw- ing the dipstick.
Engine coolant in the transmission fluid is gener- ally caused by a cooler malfunction. The only remedy is to replace the radiator as the cooler in the radiator is not a serviceable part. If coolant has circulated through the transmission, an overhaul is necessary. The torque converter should be replaced whenever a failure generates sludge and debris. This is neces- sary because normal converter flushing procedures will not remove all contaminants.
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL CHECK
Low fluid level can cause a variety of conditions because it allows the pump to take in air along with the fluid. As in any hydraulic system, air bubbles make the fluid spongy, therefore, pressures will be low and build up slowly.
Improper filling can also raise the fluid level too high. When the transmssion has too much fluid, the geartrain churns up foam and cause the same condi- tions which occur with a low fluid level.
In either case, air bubbles can cause overheating and/or fluid oxidation, and varnishing. This can interfere with normal valve, clutch, and accumulator operation. Foaming can also result in fluid escaping from the transmission vent where it may be mis- taken for a leak.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level. It is located on the right side of the engine. Be sure to wipe all dirt from dipstick handle before removing. Fluid level is checked with the engine running at curb idle speed, the transmission in NEUTRAL and the transmission fluid at normal operating tempera- ture. The engine should be running at idle speed for at least one minute, with the vehicle on level ground.
The transmission fluid level can be checked two
ways.
PROCEDURE ONE
(1) Transmission fluid must be at normal operat- ing temperature for accurate fluid level check. Drive
21 - 382
FLUID AND FILTER (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
vehicle if necessary to bring fluid temperature up to normal hot operating temperature of 82°C (180°F).
(2) Position vehicle on level surface. (3) Start and run engine at curb idle speed. (4) Apply parking brakes. (5) Shift transmission momentarily into all gear ranges. Then shift transmission back to NEUTRAL. (6) Clean top of filler tube and dipstick to keep
dirt from entering tube.
(7) Remove dipstick (Fig. 89) and check fluid level
(a) Correct acceptable level is in crosshatch area. (b) Correct maximum level is to MAX arrow
as follows:
mark.
(c) Incorrect level is at or below MIN line. (d) If fluid is low, add only enough Mopart ATF +4, type 9602, to restore correct level. Do not over- fill.
chart.
PROCEDURE TWO
(1) Start engine and apply parking brake. (2) Shift the transmission into DRIVE for approxi-
mately 2 seconds.
(3) Shift
the transmission into REVERSE for
approximately 2 seconds.
(4) Shift the transmission into PARK. (5) Hook up DRBt scan tool and select engine.
Fig.89DipstickFluidLevelMarks—Typical
1 - DIPSTICK 2 - MAXIMUM CORRECT FLUID LEVEL 3 - ACCEPTABLE FLUID LEVEL
(6) Select sensors. (7) Read the transmission temperature value. (8) Compare the fluid temperature value with the
(9) Adjust transmission fluid level shown on the
dipstick according to the chart (Fig. 90).
NOTE: After adding any fluid to the transmission, wait a minimum of 2 minutes for the oil to fully drain from the fill tube into the transmission before rechecking the fluid level.
(10) Check transmission for leaks.
Fig.9048REFluidFillGraph
AUTOMATIC TRANSMISSION - 48RE
21 - 383
DR FLUID AND FILTER (Continued) STANDARD PROCEDURE - FLUID AND FILTER REPLACEMENT
For proper service intervals (Refer to LUBRICA- TION & MAINTENANCE/MAINTENANCE SCHED- ULES - DESCRIPTION). The service fluid fill after a filter change is approximately 3.8 liters (4.0 quarts).
REMOVAL
(1) Hoist and support vehicle on safety stands. (2) Place a large diameter shallow drain pan
beneath the transmission pan.
(3) Remove bolts holding front and sides of pan to
transmission (Fig. 91).
(4) Loosen bolts holding rear of pan to transmission. (5) Slowly separate front of pan and gasket away from transmission allowing the fluid to drain into drain pan.
(6) Hold up pan and remove remaining bolt hold-
ing pan to transmission.
away from transmission.
(7) While holding pan level, lower pan and gasket
(8) Pour remaining fluid in pan into drain pan. (9) Remove screws holding filter to valve body
(Fig. 92).
(10) Separate filter from valve body and pour fluid
in filter into drain pan.
(11) Dispose of used trans fluid and filter properly.
Fig.91TransmissionPan
1 - TRANSMISSION 2 - GASKET 3 - PAN
INSTALLATION
(1) Position a new transmission oil filter onto the
valve body.
(2) Install the screws to hold the filter to the valve
body. Tighten the screws to 4 N·m (35 in.lbs.).
(3) Clean the gasket surfaces of the transmission
oil pan and transmission pan rail.
Fig.92TransmissionFilter
1 - TRANSMISSION 2 - FILTER
NOTE: The transmission pan oil gasket is reusable. Inspect the sealing surfaces of the gasket. If the sealing ribs on both surfaces appear to be in good condition, clean the gasket of any foreign material and reinstall.
(4) Position the oil pan gasket onto the oil pan. (5) Position the oil pan and gasket onto the trans- mission and install several bolts to hold the pan and gasket to the transmission.
(6) Install the remainder of the oil pan bolts.
Tighten the bolts to 13.6 N·m (125 in.lbs.).
(7) Lower vehicle and fill transmission. (Refer to 21 - TRANSMISSION/AUTOMATIC/FLUID - STAN- DARD PROCEDURE)
STANDARD PROCEDURE - TRANSMISSION FILL
To avoid overfilling transmission after a fluid change or overhaul, perform the following procedure: in
(1) Remove dipstick and insert clean funnel
transmission fill tube.
(2) Add following initial quantity of Mopart ATF
+4, Automatic Transmission Fluid, to transmission:
(a) If only fluid and filter were changed, add 3
pints (1-1/2 quarts) of ATF +4 to transmission.
(b) If transmission was completely overhauled, or torque converter was replaced or drained, add 12 pints (6 quarts) of ATF +4 to transmission. (3) Apply parking brakes. (4) Start and run engine at normal curb idle speed. (5) Apply service brakes, shift transmission through all gear ranges then back to NEUTRAL, set parking brake, and leave engine running at curb idle speed.
(6) Remove funnel, insert dipstick and check fluid level. If level is low, add fluid to bring level to MIN mark on dipstick. Check to see if the oil level
21 - 384
FLUID AND FILTER (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
is equal on both sides of the dipstick. If one side is noticably higher than the other, the dipstick has picked up some oil from the dipstick tube. Allow the oil to drain down the dipstick tube and re-check.
(7) Drive vehicle until transmission fluid is at nor-
mal operating temperature.
(8) With the engine running at curb idle speed, the gear selector in NEUTRAL, and the parking brake applied, check the transmission fluid level.
CAUTION: Do not overfill transmission, fluid foam- ing and shifting problems can result.
(9) Add fluid to bring level up to MAX arrow mark. When fluid level is correct, shut engine off, release park brake, remove funnel, and install dipstick in fill tube.
FRONT CLUTCH DESCRIPTION
The front clutch assembly (Fig. 93) is composed of the front clutch retainer, pressure plate, clutch plates, driving discs, piston, piston return spring, return spring retainer, and snap-rings. The front clutch is the forward-most component in the trans- mission geartrain and is directly behind the oil pump and is considered a driving component.
OPERATION
To apply the clutch, pressure is applied between the clutch retainer and piston. The fluid pressure is pro- vided by the oil pump, transferred through the control valves and passageways, and enters the clutch through the hub of the reaction shaft support. With pressure applied between the clutch retainer and piston, the pis- ton moves away from the clutch retainer and com- presses the clutch pack. This action applies the clutch pack, allowing torque to flow through the input shaft into the driving discs, and into the clutch plates and pressure plate that are lugged to the clutch retainer. The waved snap-ring is used to cushion the application of the clutch pack.
When pressure is released from the piston, the spring returns the piston to its fully released position and dis- engages the clutch. The release spring also helps to cushion the application of the clutch assembly. When the clutch is in the process of being released by the release spring, fluid flows through a vent and one-way ball-check-valve located in the clutch retainer. The check-valve is needed to eliminate the possibility of plate drag caused by centrifugal force acting on the residual fluid trapped in the clutch piston retainer.
DISASSEMBLY
(1) Remove the waved snap-ring, reaction plate,
clutch plates, and clutch discs.
1 - INNER PISTON SEAL 2 - CLUTCH PISTON 3 - CLUTCH PISTON SPRING RETAINER 4 - CLUTCH PLATES 5 - CLUTCH PACK SNAP-RING (WAVED) 6 - REACTION PLATE
Fig.9348REFrontClutchComponents
7 - CLUTCH DISCS 8 - RETAINER SNAP-RING
