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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 9 - CLUTCH PISTON SPRINGS 10 - OUTER PISTON SEAL 11 - FRONT CLUTCH RETAINER
DR FRONT CLUTCH (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 385
(2) Compress clutch piston retainer and piston
springs with Compressor Tool C-3863-A (Fig. 94).
(3) Remove retainer snap-ring and remove com-
pressor tool.
(4) Remove clutch piston springs (Fig. 95). Note position and number of piston springs for assembly reference.
(5) Remove clutch piston from retainer with a
(6) Remove and discard clutch piston inner and
twisting motion.
outer seals.
INSPECTION
Inspect the front clutch components. Replace the clutch discs if warped, worn, scored, burned or charred, the lugs are damaged, or if the facing is flaking off. Replace the steel plates and reaction plate if heavily scored, warped, or broken. Be sure the driving lugs on the discs and plate are also in good condition. The lugs must not be bent, cracked or damaged in any way.
Replace the piston springs and spring retainer if
either are distorted, warped or broken.
Check the lug grooves in the clutch piston retainer. The steel plates should slide freely in the slots. Replace the piston retainer if the grooves are worn or damaged. Also check action of the check ball in the piston retainer. The ball must move freely and not stick.
Fig.94RemovingFrontClutchSpringRetainer
Snap-Ring
1 - SPECIAL TOOL C-3863-A 2 - SNAP-RING
Replace the retainer bushing if worn, scored, or
there is any doubt about bushing condition.
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.9548REFrontClutchComponents
7 - CLUTCH DISCS 8 - RETAINER SNAP-RING 9 - CLUTCH PISTON SPRINGS 10 - OUTER PISTON SEAL 11 - FRONT CLUTCH RETAINER
21 - 386
FRONT CLUTCH (Continued)AUTOMATIC TRANSMISSION - 48RE
Inspect the piston and retainer seal surfaces for nicks or scratches. Minor scratches can be removed with crocus cloth. However, replace the piston and/or retainer if the seal surfaces are seriously scored.
Check the clutch piston check ball. The ball should be securely in place. Replace the piston if the ball is missing, or seized in place.
ASSEMBLY
NOTE: The 48RE transmission uses five plates and discs for the front clutch.
(1) Soak clutch discs in transmission fluid. (2) Install new inner piston seal onto the outer
diameter of the clutch retainer inner hub.
(3) Install new outer seal onto the clutch piston. Be sure seal lips of both seals face the interior of the retainer.
(4) Lubricate new inner and outer piston seals
with petroleum jelly.
(5) Install clutch piston in retainer. Use twisting motion to seat piston in bottom of retainer. A thin strip of plastic (about 0.015 - 0.020 in. thick), can be used to guide seals into place if necessary.
CAUTION: Never push the clutch piston straight in. This will fold the seals over causing leakage and clutch slip. In addition, never use any type of metal
DR
Fig.96FrontClutchSpringPosition
1 - 9 SPRING CLUTCH
tool to help ease the piston seals into place. Metal tools will cut, shave, or score the seals.
(6) Install and position nine clutch piston springs
(Fig. 96).
(7) Install spring retainer on top of piston springs. (8) Compress spring retainer and piston springs
with Tool C-3863-A.
compressor tool.
(9) Install spring retainer snap-ring and remove
(10) Install clutch plates and discs (Fig. 97). Five clutch discs, five steel plates and one reaction plate are required.
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.9748REFrontClutchComponents
7 - CLUTCH DISCS 8 - RETAINER SNAP-RING 9 - CLUTCH PISTON SPRINGS 10 - OUTER PISTON SEAL 11 - FRONT CLUTCH RETAINER
DR FRONT CLUTCH (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 387
(11) Install reaction plate followed by waved snap-
ring.
(12) Check clutch pack clearance with feeler gauge (Fig. 98). Clearance between waved spring and pres- sure plate should 2.5-4.09 mm (0.098-0.161 in.). If clearance is incorrect, clutch plates, clutch discs, snap-ring, or pressure plate may have to be changed.
Fig.99FrontServo
1 - VENT 2 - INNER PISTON 3 - PISTON 4 - SPRING 5 - RELEASE PRESSURE 6 - APPLY PRESSURE 7 - PISTON ROD
OPERATION
The application of the piston is accomplished by applying pressure between the two lands of the pis- ton. The pressure acts against the larger lower land to push the piston downward, allowing the piston rod to extend though its guide against the apply lever. Release of the servo at the 2-3 upshift is accom- plished by a combination of spring and line pressure, acting on the bottom of the larger land of the piston. The small piston is used to cushion the application of the band by bleeding oil through a small orifice in the larger piston. The release timing of the kickdown servo is very important to obtain a smooth but firm shift. The release has to be very quick, just as the front clutch application is taking place. Otherwise, engine runaway or a shift hesitation will occur. To accomplish this, the band retains its holding capacity until the front clutch is applied, giving a small amount of overlap between them.
Fig.98TypicalMethodOfMeasuringFrontClutch
PackClearance
1 - FEELER GAUGE 2 - WAVED SNAP-RING 3 - FEELER GAUGE
FRONT SERVO DESCRIPTION
The kickdown servo (Fig. 99) consists of a two-land piston with an inner piston, a piston rod and guide, and a return spring. The dual-land piston uses seal rings on its outer diameters and an O-ring for the inner piston.
AUTOMATIC TRANSMISSION - 48RE
21 - 388
FRONT SERVO (Continued) DISASSEMBLYDR
(1) Remove seal ring from rod guide (Fig. 100). (2) Remove small snap-ring from servo piston rod. Then remove piston rod, spring and washer from pis- ton.
(3) Remove and discard servo component O-ring
and seal rings.
Fig.101FrontServo
1 - VENT 2 - INNER PISTON 3 - PISTON 4 - SPRING 5 - RELEASE PRESSURE 6 - APPLY PRESSURE 7 - PISTON ROD
Fig.102FrontServo
1 - PISTON RINGS 2 - SERVO PISTON 3 - O-RING 4 - SNAP-RING 5 - PISTON ROD GUIDE 6 - SEAL RING 7 - SNAP-RING 8 - SERVO SPRING 9 - WASHER 10 - SPRING 11 - PISTON ROD
Fig.100FrontServo
1 - PISTON RINGS 2 - SERVO PISTON 3 - O-RING 4 - SNAP-RING 5 - PISTON ROD GUIDE 6 - SEAL RING 7 - SNAP-RING 8 - SERVO SPRING 9 - WASHER 10 - SPRING 11 - PISTON ROD
CLEANING
Clean the servo piston components (Fig. 101) with
solvent and dry them with compressed air.
INSPECTION
Inspect the servo components (Fig. 102). Replace the springs if collapsed, distorted or broken. Replace the guide, rod and piston if cracked, bent, or worn. Discard the servo snap-ring if distorted or warped.
Check the servo piston bore for wear. If the bore is severely scored, or damaged, it will be necessary to replace the case.
Replace any servo component if doubt exists about
condition. Do not reuse suspect parts.
ASSEMBLY
Clean and inspect front servo components. (1) Lubricate new o-ring and seal rings with petro- leum jelly and install them on piston, guide and rod.
DR FRONT SERVO (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 389
(2) Install rod in piston. Install spring and washer on rod. Compress spring and install snap-ring (Fig. 103).
(3) Disengage cable eyelet at transmission shift lever and pull cable adjuster out of mounting bracket (Fig. 104) or (Fig. 105).
Fig.103FrontServo
1 - PISTON RINGS 2 - SERVO PISTON 3 - O-RING 4 - SNAP-RING 5 - PISTON ROD GUIDE 6 - SEAL RING 7 - SNAP-RING 8 - SERVO SPRING 9 - WASHER 10 - SPRING 11 - PISTON ROD
GEARSHIFT CABLE DIAGNOSIS AND TESTING - GEARSHIFT CABLE
Fig.104GearshiftCableatTransmission-RFE
1 - GEARSHIFT CABLE 2 - RFE TRANSMISSION 3 - MANUAL LEVER
(1) Engine starts must be possible with shift lever in PARK or NEUTRAL positions only. Engine starts must not be possible in any other gear position.
(2) With the shift lever in the:
(a) PARK position - Apply upward force on the shift arm and remove pressure. Engine starts must be possible.
(b) PARK position - Apply downward force on the shift arm and remove pressure. Engine starts must be possible.
(c) NEUTRAL position - Normal position. Engine
starts must be possible.
(d) NEUTRAL position - Engine running and brakes applied, apply upward force on the shift arm. Transmission shall not be able to shift from neutral to reverse.
REMOVAL
(1) Shift transmission into PARK. (2) Raise vehicle.
Fig.105GearshiftCableatTransmission-RE
1 - GEARSHIFT CABLE 2 - RE TRANSMISSION 3 - MANUAL LEVER
21 - 390
GEARSHIFT CABLE (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(4) Lower the vehicle. (5) Remove the dash panel insulation pad as nec- essary to access the gearshift cable grommet (Fig. 106).
(6) Remove grommet from the dash panel. (7) Remove any steering column trim necessary to
access the gearshift cable and BTSI mechanism.
(8) Disconnect the BTSI wiring connector. (9) Disconnect cable at lower column bracket and shift lever pin and pull the cable through the dash panel opening into the vehicle (Fig. 107).
INSTALLATION
(1) Route the transmission end of the gearshift cable through the opening in the dash panel (Fig. 108).
(2) Seat the cable grommet into the dash panel
opening.
(3) Snap the cable into the steering column bracket so the retaining ears (Fig. 109) are engaged and snap the cable eyelet onto the shift lever ball stud.
Fig.106GearshiftCableattheDashPanel
1 - GEARSHIFT CABLE 2 - GROMMET
Fig.108GearshiftCableattheDashPanel
1 - GEARSHIFT CABLE 2 - GROMMET
Fig.107GearshiftCableatSteeringColumn
1 - STEERING COLUMN 2 - GEARSHIFT CABLE 3 - GEARSHIFT CABLE LOCK TAB 4 - BTSI SOLENOID LOCK TAB 5 - BTSI CONNECTOR
(10) Remove gearshift cable from vehicle.
Fig.109GearshiftCableatSteeringColumn
1 - STEERING COLUMN 2 - GEARSHIFT CABLE 3 - GEARSHIFT CABLE LOCK TAB 4 - BTSI SOLENOID LOCK TAB 5 - BTSI CONNECTOR
DR GEARSHIFT CABLE (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 391
(4) Raise the vehicle. (5) Place the transmission manual shift lever in the “PARK” detent (rearmost) position and rotate prop shaft to ensure transmission is in PARK.
(6) Route the gearshift cable through the transmis- sion mounting bracket and secure the cable by snap- ping the cable retaining ears into the transmission bracket and snapping the cable eyelet on the manual shift lever ball stud. (7) Lower vehicle. (8) Lock the shift cable adjustment by pressing the cable adjuster lock tab downward until it snaps into place.
(9) Check for proper operation of the transmission
range sensor.
nism as necessary.
(10) Adjust the gearshift cable and BTSI mecha-
(5) Verify transmission shift
lever is in PARK detent by moving lever fully rearward. Last rearward detent is PARK position.
(6) Verify positive engagement of
transmission park lock by attempting to rotate propeller shaft. Shaft will not rotate when park lock is engaged.
(7) Snap the cable eyelet onto the transmission
manual shift lever. (8) Lower vehicle. (9) Lock shift cable by pressing cable adjuster lock
tab downward until it snaps into place.
(10) Check engine starting. Engine should start
only in PARK and NEUTRAL
ADJUSTMENTS
GEARSHIFT CABLE
is CORRECT if
Check adjustment by starting the engine in PARK and NEUTRAL. Adjustment the engine starts only in these positions. Adjustment is INCORRECT if the engine starts in one but not both positions. If the engine starts in any position other than PARK or NEUTRAL, or if the engine will not start at all, the transmission range sensor may be faulty.
Gearshift Adjustment Procedure
(1) Shift transmission into PARK. (2) Release cable adjuster lock tab (underneath the
steering column) (Fig. 110) to unlock cable.
(3) Raise vehicle. (4) Disengage the cable eyelet from the transmis-
sion manual shift lever.
Fig.110GearshiftCableatSteeringColumn
1 - STEERING COLUMN 2 - GEARSHIFT CABLE 3 - GEARSHIFT CABLE LOCK TAB 4 - BTSI SOLENOID LOCK TAB 5 - BTSI CONNECTOR
21 - 392
AUTOMATIC TRANSMISSION - 48RE
DR
OIL PUMP DESCRIPTION
The oil pump (Fig. 111) is located in the pump housing inside the bell housing of the transmission case. The oil pump consists of an inner and outer gear, a housing, and a reaction shaft support.
OPERATION
the
clearance between the
As the torque converter rotates, the converter hub rotates the inner and outer gears. As the gears rotate, teeth increases in the crescent area, and creates a suction at the inlet side of the pump. This suction draws fluid through the pump inlet from the oil pan. As the clearance between the gear teeth in the crescent area decreases, it forces pressurized fluid into the pump outlet and to the valve body.
gear
1 - OIL SEAL 2 - VENT BAFFLE 3 - OIL PUMP BODY 4 - GASKET 5 - REACTION SHAFT SUPPORT 6 - SEAL RINGS
Fig.111OilPumpAssembly
7 - BOLTS (6) 8 - #1 THRUST WASHER (SELECTIVE) 9 - INNER GEAR 10 - OUTER GEAR 11 - “O” RING 12 - TORQUE CONVERTER SEAL RING
DR OIL PUMP (Continued) DISASSEMBLY
AUTOMATIC TRANSMISSION - 48RE
21 - 393
(1) Mark position of support in oil pump body for assembly alignment reference. Use scriber or paint to make alignment marks.
(2) Place pump body on two wood blocks. (3) Remove reaction shaft support bolts and sepa-
rate support from pump body (Fig. 112).
(4) Remove pump inner and outer gears (Fig. 113). (5) Remove o-ring seal from pump body (Fig. 114).
Discard seal after removal.
(6) Remove oil pump seal with Remover Tool
C-3981. Discard seal after removal.
Fig.113PumpGears
1 - GEAR BORE 2 - PUMP BODY 3 - INNER GEAR 4 - OUTER GEAR
Fig.112ReactionShaftSupport
1 - OIL PUMP 2 - REACTION SHAFT SUPPORT
CLEANING
Clean pump and support components with solvent
and dry them with compressed air.
INSPECTION
Check condition of
the seal rings and thrust washer on the reaction shaft support. The seal rings do not need to be replaced unless cracked, broken, or severely worn.
Inspect the pump and support components. Replace the pump or support if the seal ring grooves or machined surfaces are worn, scored, pitted, or dam- aged. Replace the pump gears if pitted, worn chipped, or damaged.
Inspect the pump bushing. Then check the reaction shaft support bushing. Replace either bushing only if heavily worn, scored or damaged. It is not necessary to replace the bushings unless they are actually dam- aged.
Clearance between outer gear and reaction shaft housing should be 0.010 to 0.063 mm (0.0004 to 0.0025 in.). Clearance between inner gear and reac- tion shaft housing should be 0.010 to 0.063 mm (0.0004 to 0.0025 in.). Both clearances can be mea-
sured at the same time by installing the gears in the pump body and measure pump component clearances as follows:
(1) Position an appropriate piece of Plastigage™
across both gears.
tion shaft housing.
(2) Align the plastigage to a flat area on the reac-
(3) Install the reaction shaft to the pump housing. (4) Separate the reaction shaft housing from the pump housing and measure the Plastigage™ follow- ing the instructions supplied with it.
Clearance between inner gear tooth and outer gear should be 0.051 to 0.19 mm (0.002 to 0.0075 in.). Measure clearance with an appropriate feeler gauge (Fig. 115).
Clearance between outer gear and pump housing should be 0.10 to 0.229 mm (0.004 to 0.009 in.). Mea- sure clearance with an appropriate feeler gauge.
ASSEMBLY
(1) Lubricate pump gears with transmission fluid
and install them in pump body.
(2) Install thrust washer on reaction shaft support hub. Lubricate washer with petroleum jelly or trans- mission fluid before installation.
(3) If reaction shaft seal rings are being replaced, install new seal rings on support hub. Lubricate seal rings with transmission fluid or petroleum jelly after installation. Squeeze each ring until ring ends are securely hooked together.
21 - 394
OIL PUMP (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
1 - OIL SEAL 2 - VENT BAFFLE 3 - OIL PUMP BODY 4 - GASKET 5 - REACTION SHAFT SUPPORT 6 - SEAL RINGS
Fig.114OilPumpAssembly
7 - BOLTS (6) 8 - #1 THRUST WASHER (SELECTIVE) 9 - INNER GEAR 10 - OUTER GEAR 11 - “O” RING 12 - TORQUE CONVERTER SEAL RING
CAUTION: The reaction shaft support seal rings will break if overspread, or twisted. If new rings are being installed, spread them only enough for instal- lation. Also be very sure the ring ends are securely hooked together after installation. Otherwise, the rings will either prevent pump installation, or break during installation.
(4) Align and install reaction shaft support on
pump body.
(5) Install bolts attaching reaction shaft support to pump. Tighten bolts to 20 N·m (175 in. lbs.) torque.
Fig.115CheckingPumpGearTipClearance
1 - FEELER GAUGE 2 - INNER GEAR 3 - OUTER GEAR
DR OIL PUMP (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 395
(6) Install new pump seal with Installer Tool C-3860-A (Fig. 116). Use hammer or mallet to tap seal into place.
(7) Install new o-ring on pump body. Lubricate oil
seal and o-ring with petroleum jelly.
(8) Cover pump assembly to prevent dust entry
and set aside for assembly installation.
Fig.116OilPumpSeal
1 - SPECIAL TOOL C-3860-A 2 - PUMP BODY 3 - PUMP SEAL
OUTPUT SHAFT FRONT BEARING REMOVAL
(1) Remove overdrive unit from the vehicle. (2) Remove overdrive geartrain from housing. (3) Remove snap-ring holding output shaft front
bearing to overdrive geartrain. (Fig. 117).
(4) Pull bearing from output shaft.
INSTALLATION
(1) Place replacement bearing in position on geartrain with locating retainer groove toward the rear.
(2) Push bearing onto shaft until the snap-ring
(3) Install snap-ring to hold bearing onto output
groove is visible.
shaft.
(4) Install overdrive geartrain into housing. (5) Install overdrive unit in vehicle.
Fig.117OutputShaftFrontBearing
1 - OUTPUT SHAFT FRONT BEARING 2 - SNAP-RING 3 - OUTPUT SHAFT 4 - GROOVE TO REAR 5 - OVERDRIVE GEARTRAIN
OUTPUT SHAFT REAR BEARING REMOVAL
(1) Remove overdrive unit from the vehicle. (Refer to 21 - TRANSMISSION/AUTOMATIC/OVERDRIVE - REMOVAL)
(2) Remove overdrive geartrain from housing. (3) Remove snap-ring holding output shaft rear
bearing into overdrive housing (Fig. 118).
(4) Using a suitable driver inserted through the
rear end of housing, drive bearing from housing.
Fig.118OutputShaftRearBearing
1 - OUTPUT SHAFT REAR BEARING 2 - OVERDRIVE HOUSING 3 - SNAP-RING
AUTOMATIC TRANSMISSION - 48RE
21 - 396
OUTPUT SHAFT REAR BEARING (Continued) INSTALLATIONOPERATION
DR
(1) Place replacement bearing in position in hous-
(2) Using a suitable driver, drive bearing into
housing until the snap-ring groove is visible.
(3) Install snap-ring to hold bearing into housing
ing.
(Fig. 118).
(4) Install overdrive geartrain into housing. (5) Install overdrive unit in vehicle.
OVERDRIVE CLUTCH DESCRIPTION
The overdrive clutch (Fig. 119) is composed of the pressure plate, clutch plates, holding discs, overdrive piston retainer, piston, piston spacer, and snap-rings. The overdrive clutch is the forwardmost component in the transmission overdrive unit and is considered a holding component. The overdrive piston retainer, piston, and piston spacer are located on the rear of the main transmission case.
NOTE: The number of discs and plates may vary with each engine and vehicle combination.
To apply the clutch, pressure is applied between the piston retainer and piston. The fluid pressure is provided by the oil pump, transferred through the control valves and passageways, and enters the clutch through passages at the lower rear portion of the valve body area. With pressure applied between the piston retainer and piston, the piston moves away from the piston retainer and compresses the clutch pack. This action applies the clutch pack, allowing torque to flow through the intermediate shaft into the overdrive planetary gear set. The over- drive clutch discs are attached to the overdrive clutch hub while the overdrive clutch plates, reaction plate, and pressure plate are lugged to the overdrive hous- ing. This allows the intermediate shaft to transfer the engine torque to the planetary gear and overrun- ning clutch. This drives the planetary gear inside the annulus, which is attached to the overdrive clutch drum and output shaft, creating the desired gear ratio. The waved snap-ring is used to cushion the application of the clutch pack for the 5 disc version of the overdrive clutch. The 6 disc overdrive clutch does not use a waved snap-ring.
1 - REACTION PLATE
Fig.119OverdriveClutch
2 - PRESSURE PLATE
DR
AUTOMATIC TRANSMISSION - 48RE
21 - 397
OVERDRIVE SWITCH DESCRIPTION
The overdrive OFF (control) switch is located in the shift lever arm (Fig. 120). The switch is a momentary contact device that signals the PCM to toggle current status of the overdrive function.
Fig.121OverdriveOffSwitchRetainer
1 - GEAR SHIFT LEVER 2 - OVERDRIVE OFF SWITCH RETAINER 3 - PLASTIC TRIM TOOL
(2) Pull the switch outwards to release it from the
connector in the lever (Fig. 122)
Fig.122RemovetheOverdriveOffSwitch
1 - GEAR SHIFT LEVER 2 - OVERDRIVE OFF SWITCH
INSTALLATION
NOTE: There is enough slack in the wire to pull out the connector from the lever.
(1) Pull the connector out of the lever just enough
to grasp it.
CAUTION: Be careful not to bend the pins on the overdrive off switch. Use care when installing the switch, as it is not indexed, and can be accidentally installed incorrectly.
Fig.120OverdriveOffSwitch
OPERATION
At key-on, overdrive operation is allowed. Pressing the switch once causes the overdrive OFF mode to be entered and the overdrive OFF switch lamp to be illuminated. Pressing the switch a second time causes normal overdrive operation to be restored and the overdrive lamp to be turned off. The overdrive OFF mode defaults to ON after the ignition switch is cycled OFF and ON. The normal position for the con- trol switch is the ON position. The switch must be in this position to energize the solenoid and allow a 3-4
upshift. The control switch indicator light illuminates only when the overdrive switch is turned to the OFF position, or when illuminated by the transmission control module.DIAGNOSIS AND TESTING - OVERDRIVE ELECTRICAL CONTROLS
The overdrive off switch, valve body solenoid, case connectors and related wiring can all be tested with a 12 volt test lamp or a volt/ohmmeter. Check conti- nuity of each component when diagnosis indicates this is necessary.
Switch and solenoid continuity should be checked whenever the transmission fails to shift into fourth gear range.
REMOVAL
(1) Using a plastic trim tool, remove the overdrive
off switch retainer from the shift lever (Fig. 121).
21 - 398
OVERDRIVE SWITCH (Continued)AUTOMATIC TRANSMISSION - 48RE
(2) Install the overdrive off switch into the connec-
tor (Fig. 123)
DR
CAUTION: Support the overdrive unit with a jack before moving it rearward. This is necessary to pre- vent damaging the intermediate shaft. Do not allow the shaft to support the entire weight of the over- drive unit.
Fig.123InstalltheOverdriveOffSwitch
1 - GEAR SHIFT LEVER 2 - OVERDRIVE OFF SWITCH WIRING CONNECTOR 3 - OVERDRIVE OFF SWITCH
(3) Push the overdrive off switch and wiring into
(4) Install the overdrive off switch retainer onto
the shift lever.
the shift lever.
OVERDRIVE UNIT REMOVAL
(1) Shift transmission into PARK. (2) Raise vehicle. (3) Remove transfer case, if equipped. (4) Mark propeller shaft universal joint(s) and axle pinion yoke, or the companion flange and flange yoke, for alignment reference at installation, if neces- sary.
(5) Disconnect and remove the rear propeller shaft, if necessary. (Refer to 3 - DIFFERENTIAL & DRIV- ELINE/PROPELLER SHAFT/PROPELLER SHAFT - REMOVAL)
(6) Remove transmission oil pan, remove gasket,
drain oil and reinstall pan.
(7) If overdrive unit had malfunctioned, or if fluid is contaminated, remove entire transmission. If diag- nosis indicated overdrive problems only, remove just the overdrive unit.
(8) Support transmission with transmission jack. (9) Remove bolts attaching overdrive unit to trans-
mission (Fig. 124).
Fig.124OverdriveUnitBolts
1 - OVERDRIVE UNIT 2 - ATTACHING BOLTS (7)
(10) Carefully work overdrive unit off intermediate shaft. Do not tilt unit during removal. Keep it as level as possible.
(11) If overdrive unit does not require service, immediately insert Alignment Tool 6227-2 in splines of planetary gear and overrunning clutch to prevent splines from rotating out of alignment. If misalign- ment occurs, overdrive unit will have to be disassem- bled in order to realign splines.
(12) Remove and retain overdrive piston thrust
