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Fig.227TransmissionOutputSpeedSensor
1 - TRANSMISSION OUTPUT SHAFT SPEED SENSOR 2 - SEAL
OPERATION
Speed sensor signals are triggered by the park gear lugs as they rotate past the sensor pickup face. Input signals from the sensor are sent to the trans- mission control module for processing. Signals from this sensor are shared with the powertrain control module.
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AUTOMATIC TRANSMISSION - 48RE
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THROTTLE VALVE CABLE DESCRIPTION
Transmission throttle valve cable (Fig. 228) adjust- ment is extremely important to proper operation. This adjustment positions the throttle valve, which controls shift speed, quality, and part-throttle down- shift sensitivity.
If cable setting is too loose, early shifts and slip- page between shifts may occur. If the setting is too tight, shifts may be delayed and part throttle down- shifts may be very sensitive.
Fig.229ThrottleValveCableatThrottleLinkage
1 - THROTTLE LINKAGE 2 - THROTTLE VALVE CABLE LOCKING CLIP 3 - THROTTLE VALVE CABLE
lever to either move ahead of, or lag behind the lever on the throttle body.
ADJUSTMENT VERIFICATION
(1) Turn ignition key to OFF position. (2) Remove air cleaner. (3) Verify that lever on throttle body is at curb idle position (Fig. 230). Then verify that the transmission throttle lever (Fig. 231) is also at idle (fully forward) position.
(4) Slide cable off attachment stud on throttle body
lever.
stud on throttle body lever:
(5) Compare position of cable end to attachment † Cable end and attachment stud should be aligned (or centered on one another) to within 1 mm (0.039 in.) in either direction (Fig. 232). † If cable end and attachment stud are misaligned (off center), cable will have to be adjusted as described in Throttle Valve Cable Adjustment proce- dure.
(6) Reconnect cable end to attachment stud. Then with aid of a helper, observe movement of transmis- sion throttle lever and lever on throttle body.
Fig.228ThrottleValveCableAttachment-At
Engine
1 - THROTTLE VALVE CABLE 2 - CABLE BRACKET 3 - THROTTLE BODY LEVER 4 - ACCELERATOR CABLE 5 - SPEED CONTROL CABLE
The transmission throttle valve is operated by a cam on the throttle lever. The throttle lever is oper- ated by an adjustable cable (Fig. 229). The cable is attached to an arm mounted on the throttle lever shaft. A retaining clip at the engine-end of the cable is removed to provide for cable adjustment. The retaining clip is then installed back onto the throttle valve cable to lock in the adjustment.
ADJUSTMENTS - THROTTLE VALVE CABLE
A correctly adjusted throttle valve cable will cause the throttle lever on the transmission to move simul- taneously with the throttle body lever from the idle position. Proper adjustment will allow simultaneous movement without causing the transmission throttle
DR THROTTLE VALVE CABLE (Continued)
AUTOMATIC TRANSMISSION - 48RE
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Fig.230ThrottleValveCableAttachment-At
Engine
1 - THROTTLE VALVE CABLE 2 - CABLE BRACKET 3 - THROTTLE BODY LEVER 4 - ACCELERATOR CABLE 5 - SPEED CONTROL CABLE
Fig.231ThrottleValveCableatTransmission
1 - TRANSMISSION SHIFTER CABLE 2 - THROTTLE VALVE CABLE 3 - TRANSFER CASE SHIFTER CABLE 4 - TRANSFER CASE SHIFTER CABLE BRACKET RETAINING BOLT (1 OR 2) 5 - THROTTLE VALVE CABLE BRACKET RETAINING BOLT 6 - ELECTRICAL CONNECTORS 7 - TRANSMISSION FLUID LINES
Fig.232ThrottleValveCableatThrottleLinkage
1 - THROTTLE LINKAGE 2 - THROTTLE VALVE CABLE LOCKING CLIP 3 - THROTTLE VALVE CABLE
† If both levers move simultaneously from idle to half-throttle and back to idle position, adjustment is correct. † If transmission throttle lever moves ahead of, or lags behind throttle body lever, cable adjustment will be necessary. Or, if throttle body lever prevents transmission lever from returning to closed position, cable adjustment will be necessary.
ADJUSTMENT PROCEDURE
(1) Turn ignition switch to OFF position. (2) Remove air cleaner if necessary. (3) Disconnect cable end from attachment stud. Carefully slide cable off stud. Do not pry or pull cable off.
(4) Verify that transmission throttle lever is in fully closed position. Then be sure lever on throttle body is at curb idle position.
(5) Pry the T.V. cable lock (A) into the UP position (Fig. 232). This will unlock the cable and allow for readjustment.
(6) Apply just enough tension on the T.V. cable (B) to remove any slack in the cable.Pulling too tight will cause the T.V. lever on the transmission to move out of its idle position, which will result
DR
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THROTTLE VALVE CABLE (Continued)AUTOMATIC TRANSMISSION - 48RE
in an incorrect T.V. cable adjustment. Slide the sheath of the T.V. cable (D) back and forth until the centerlines of the T.V. cable end (B) and the throttle bell crank lever (C) are aligned within one millimeter (1mm) (Fig. 232).
(7) While holding the T.V. cable in the set position push the T.V. cable lock (A) into the down position (Fig. 232). This will lock the present T.V. cable adjustment.
NOTE: Be sure that as the cable is pulled forward and centered on the throttle lever stud, the cable housing moves smoothly with the cable. Due to the angle at which the cable housing enters the spring housing, the cable housing may bind slightly and create an incorrect adjustment.
(8) Reconnect the T.V. cable (B) to the throttle
bellcrank lever (C).
(9) Check cable adjustment. Verify transmission throttle lever and lever on throttle body move simul- taneously.
Fig.233TorqueConverterAssembly
1 - TURBINE 2 - IMPELLER 3 - HUB 4 - STATOR 5 - FRONT COVER 6 - CONVERTER CLUTCH DISC 7 - DRIVE PLATE
TORQUE CONVERTER DESCRIPTION
The torque converter (Fig. 233)
is a hydraulic device that couples the engine crankshaft to the transmission. The torque converter consists of an outer shell with an internal turbine, a stator, an overrunning clutch, an impeller and an electronically applied converter clutch. The converter clutch pro- vides reduced engine speed and greater fuel economy when engaged. Clutch engagement also provides reduced transmission fluid temperatures. The torque converter hub drives the transmission oil (fluid) pump.
The torque converter is a sealed, welded unit that
is not repairable and is serviced as an assembly.
CAUTION: The torque converter must be replaced if a transmission failure resulted in large amounts of metal or fiber contamination in the fluid. If the fluid is contaminated, transmission fluid cooler(s) and lines.
flush the all
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DR TORQUE CONVERTER (Continued)
IMPELLER
The impeller (Fig. 234) is an integral part of the converter housing. The impeller consists of curved blades placed radially along the inside of the housing on the transmission side of the converter. As the con- verter housing is rotated by the engine, so is the impeller, because they are one and the same and are the driving members of the system.
1 - ENGINE FLEXPLATE 2 - OIL FLOW FROM IMPELLER SECTION INTO TURBINE SECTION 3 - IMPELLER VANES AND COVER ARE INTEGRAL
Fig.234Impeller
4 - ENGINE ROTATION 5 - ENGINE ROTATION
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TORQUE CONVERTER (Continued) TURBINEThe turbine (Fig. 235) is the output, or driven, member of the converter. The turbine is mounted within the housing opposite the impeller, but is not attached to the housing. The input shaft is inserted through the center of the impeller and splined into the turbine. The design of the turbine is similar to the impeller, except the blades of the turbine are curved in the opposite direction.
DR
1 - TURBINE VANE 2 - ENGINE ROTATION 3 - INPUT SHAFT
Fig.235Turbine
4 - PORTION OF TORQUE CONVERTER COVER 5 - ENGINE ROTATION 6 - OIL FLOW WITHIN TURBINE SECTION
AUTOMATIC TRANSMISSION - 48RE
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DR TORQUE CONVERTER (Continued) STATOR
The stator assembly (Fig. 236) is mounted on a sta- tionary shaft which is an integral part of the oil pump. The stator is located between the impeller and turbine within the torque converter case (Fig. 237). The stator contains an over-running clutch, which allows the stator to rotate only in a clockwise direc- tion. When the stator is locked against the over-run- ning clutch, the torque multiplication feature of the torque converter is operational.
Fig.236StatorComponents
1 - CAM (OUTER RACE) 2 - ROLLER 3 - SPRING 4 - INNER RACE
TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 238) was installed to improve the efficiency of the torque converter that is lost to the slippage of the fluid coupling. Although the fluid cou- pling provides smooth, shock-free power transfer, it is natural for all fluid couplings to slip. If the impeller and turbine were mechanically locked together, a zero slippage condition could be obtained. A hydraulic piston was added to the turbine, and a friction mate- rial was added to the inside of the front cover to pro- vide this mechanical lock-up.
Fig.237StatorLocation
1 - STATOR 2 - IMPELLER 3 - FLUID FLOW 4 - TURBINE
Fig.238TorqueConverterClutch(TCC)
1 - IMPELLER FRONT COVER 2 - THRUST WASHER ASSEMBLY 3 - IMPELLER 4 - STATOR 5 - TURBINE 6 - PISTON 7 - FRICTION DISC
AUTOMATIC TRANSMISSION - 48RE
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TORQUE CONVERTER (Continued) OPERATIONThe converter impeller (Fig. 239) (driving member), which is integral to the converter housing and bolted to the engine drive plate, rotates at engine speed. The converter turbine (driven member), which reacts from fluid pressure generated by the impeller, rotates and turns the transmission input shaft.
DR
TURBINE
As the fluid that was put into motion by the impel- ler blades strikes the blades of the turbine, some of the energy and rotational force is transferred into the turbine and the input shaft. This causes both of them (turbine and input shaft) to rotate in a clockwise direction following the impeller. As the fluid is leav- ing the trailing edges of the turbine’s blades it con- tinues in a “hindering” direction back toward the impeller. If the fluid is not redirected before it strikes the impeller, it will strike the impeller in a direction that would tend to slow it down.
1 - APPLY PRESSURE 2 - THE PISTON MOVES SLIGHTLY FORWARD
Fig.239TorqueConverterFluidOperation 3 - RELEASE PRESSURE 4 - THE PISTON MOVES SLIGHTLY REARWARD
DR TORQUE CONVERTER (Continued) STATOR
Torque multiplication is achieved by locking the stator’s over-running clutch to its shaft (Fig. 240). Under stall conditions the turbine is stationary and the oil leaving the turbine blades strikes the face of the stator blades and tries to rotate them in a coun- terclockwise direction. When this happens the over- running clutch of the stator locks and holds the stator from rotating. With the stator locked, the oil strikes the stator blades and is redirected into a “helping” direction before it enters the impeller. This circulation of oil from impeller to turbine, turbine to stator, and stator to impeller, can produce a maxi- mum torque multiplication of about 1.75:1. As the turbine begins to match the speed of the impeller, the fluid that was hitting the stator in such as way as to cause it to lock-up is no longer doing so. In this con- dition of operation, the stator begins to free wheel and the converter acts as a fluid coupling.
Fig.240StatorOperation
1 - DIRECTION STATOR WILL FREE WHEEL DUE TO OIL PUSHING ON BACKSIDE OF VANES 2 - FRONT OF ENGINE 3 - INCREASED ANGLE AS OIL STRIKES VANES 4 - DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING AGAINST STATOR VANES
TORQUE CONVERTER CLUTCH (TCC)
The
torque
converter
clutch is hydraulically applied or released when fluid is feed or vented from the hydraulic circuit by the torque converter control (TCC) solenoid on the valve body. The torque con- verter clutch is controlled by the Powertrain Control Module (PCM). The torque converter clutch engages in fourth gear, and in third gear under various con- ditions, such as when the O/D switch is OFF, or when the vehicle is cruising on a level surface after the vehicle has warmed up. The torque converter
AUTOMATIC TRANSMISSION - 48RE
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clutch may disengage momentarily when an increase in engine load is sensed by the PCM, such as when the vehicle begins to go uphill or the throttle pres- sure is increased.
REMOVAL
(1) Remove transmission and torque converter
from vehicle.
(2) Place a suitable drain pan under the converter
housing end of the transmission.
CAUTION: Verify that transmission is secure on the lifting device or work surface, the center of gravity of the transmission will shift when the torque con- verter is removed creating an unstable condition. The torque converter is a heavy unit. Use caution when separating the torque converter from the transmission.
(3) Pull the torque converter forward until the cen-
ter hub clears the oil pump seal.
(4) Separate the torque converter from the trans-
mission.
INSTALLATION
Check converter hub and drive notches for sharp edges, burrs, scratches, or nicks. Polish the hub and notches with 320/400 grit paper or crocus cloth if nec- essary. The hub must be smooth to avoid damaging the pump seal at installation.
(1) Lubricate oil pump seal lip with transmission
(2) Place torque converter in position on transmis-
CAUTION: Do not damage oil pump seal or bushing while inserting torque converter into the front of the transmission.
(3) Align torque converter to oil pump seal open-
(4) Insert torque converter hub into oil pump. (5) While pushing torque converter inward, rotate converter until converter is fully seated in the oil pump gears.
(6) Check converter seating with a scale and straightedge (Fig. 241). Surface of converter lugs should be 19mm (0.75 in.) to the rear of the straight- edge when converter is fully seated.
(7) If necessary, temporarily secure converter with
C-clamp attached to the converter housing.
(8) Install the transmission in the vehicle.
fluid.
sion.
ing.
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TORQUE CONVERTER (Continued)AUTOMATIC TRANSMISSION - 48RE
(9) Fill the transmission with the recommended
fluid.
DR
is shut down for lengthy periods. Production valves have a hose nipple at one end, while the opposite end is threaded for a flare fitting. All valves have an arrow (or similar mark) to indicate direction of flow through the valve.
STANDARD PROCEDURE - TORQUE CONVERTER DRAINBACK VALVE
The converter drainback check valve is located in the cooler outlet (pressure) line near the radiator tank. The valve prevents fluid drainback when the vehicle is parked for lengthy periods. The valve check ball is spring loaded and has an opening pressure of approximately 2 psi.
The valve is serviced as an assembly;
it is not repairable. Do not clean the valve if restricted, or contaminated by sludge, or debris. If the valve fails, or if a transmission malfunction occurs that gener- ates significant amounts of sludge and/or clutch par- ticles and metal the valve must be replaced.
shavings,
The valve must be removed whenever the cooler and lines are reverse flushed. The valve can be flow tested when necessary. The procedure is exactly the same as for flow testing a cooler.
If the valve is restricted, installed backwards, or in the wrong line, it will cause an overheating condition and possible transmission failure.
CAUTION: The drainback valve is a one-way flow device. It must be properly oriented in terms of flow direction for the cooler to function properly. The valve must be installed in the pressure line. Other- wise flow will be blocked and would cause an over- heating condition and eventual transmission failure.
Fig.241TypicalMethodOfCheckingConverter
Seating
1 - SCALE 2 - STRAIGHTEDGE
TORQUE CONVERTER DRAINBACK VALVE DESCRIPTION
The drainback valve is located in the transmission
cooler outlet (pressure) line.
OPERATION
The valve prevents fluid from draining from the converter into the cooler and lines when the vehicle
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AUTOMATIC TRANSMISSION - 48RE
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TRANSMISSION RANGE SENSOR DESCRIPTION
The Transmission Range Sensor (TRS) (Fig. 242) has 3 primary functions: † Provide a PARK/NEUTRAL start signal to the engine controller and the starter relay. † Turn the Back-up lamps on when the transmis- sion is in REVERSE and the engine (ignition) is on. † Provide a transmission range signal to the instrument cluster.
OPERATION
As the switch moves through its linear motion (Fig. 243) contacts slide across a circuit board which changes the resistance between the range sensing pins of the switch. A power supply on the instrument cluster provides a regulated voltage signal to the switch. The return signal is decoded by the cluster, which then controls the PRNDL display to corre- spond with the correct transmission range. A bus message of transmission range is also sent by the cluster. In REVERSE range a second contact set closes the circuit providing power to the reverse lamps.
Fig.242TransmissionRangeSensor
The sensor is mounted in the transmission housing near the valve body, just above the pan rail. It’s in the same position as the Park/Neutral switch on other transmissions. The TRS contacts a cammed surface on the manual valve lever. The cammed sur- face translates the rotational motion of the manual lever into the linear motion of the sensor. The cammed surface on the manual lever is comprised of two parts controlling the TRS signal: The insulator portion contacts the switch poppet when the manual lever is not in PARK or NEUTRAL. The manual lever itself contacts the poppet when the lever is in PARK or NEUTRAL; providing a ground for the sig- nal from the starter relay and the JTEC engine con- troller.
Fig.243TransmissionRangeSensorLinear
Movement
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TRANSMISSION RANGE SENSOR (Continued)AUTOMATIC TRANSMISSION - 48RE
Mechanical State
Electronic Display (Ignition Unlocked)
Electronic Display
(Ignition On)
Indicated Gear Position
DIAGNOSIS AND TESTING - TRANSMISSION RANGE SENSOR (TRS)
NOTE: For all circuit identification in the following steps, Refer to the appropriate Wiring Information.
(1) Raise vehicle on suitable hoist. (2) Disconnect the vehicle’s shift cable from the
manual lever.
(3) With the manual lever in the PARK position (the PARK position is with the manual lever moved to the full rearward position), measure the resistance between the Park/Neutral Position Sense pin of the TRS and the transmission case. The resistance should be less than 5 ohms.
DR
Transmission Status Vehicle is in PARK with the pawl engaged. The PARK pawl is disengaged and the vehicle is free to roll, but REVERSE is not engaged. The transmission is hydraulically in REVERSE. The transmission is transitioning between REVERSE and NEUTRAL. The vehicle is in NEUTRAL. The transmission is transitioning between NEUTRAL and DRIVE, but is not in DRIVE. The transmission is hydraulically in DRIVE. The transmission is hydraulically in Manual SECOND. The transmission is hydraulically in Manual FIRST.
Column Shifter Position In the PARK gate.
Between the PARK and REVERSE gates.
In the REVERSE gate.
Between the REVERSE and NEUTRAL gates.
In the NEUTRAL gate. Between the NEUTRAL and DRIVE gates.
In the DRIVE gate,
In the SECOND gate.
In the FIRST gate.
(4) With the manual lever in the NEUTRAL posi- tion (the NEUTRAL position is with the manual lever moved two detents forward of the full rearward position), measure the resistance between the Park/ Neutral Position Sense pin of the TRS and the trans- mission case. The resistance should be less than 5
ohms.(5) If the resistance is greater than 5 ohms in either of the previous steps, check for a dirty contact between the tip of the TRS rod and the valve body manual lever. If the contact is OK, replace the TRS. (6) With the manual lever in the REVERSE posi- tion (the REVERSE position is with the manual lever moved one detent forward of the full rearward posi- tion), measure the resistance between the Fused Ignition Switch Output and the Back-up Lamp feed pins of the TRS. The resistance should be less than 5
DR TRANSMISSION RANGE SENSOR (Continued)
AUTOMATIC TRANSMISSION - 48RE
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ohms. If the resistance is greater than 5 ohms, replace the TRS.
(7) With the manual lever in the PARK position (the PARK position is with the manual lever moved to the full rearward position), measure the resistance between the Transmission Range Sensor MUX and the Transmission Range Sensor 5V Supply pins of the TRS. The resistance should be 522.2 ohms. If the resistance is not correct, replace the TRS.
(8) With the manual lever in the REVERSE posi- tion (the REVERSE position is with the manual lever moved one detent forward of the full rearward posi- tion), measure the resistance between the Transmis- sion Range Sensor MUX and the Transmission Range Sensor 5V Supply pins of the TRS. The resistance should be 206.2 ohms. If the resistance is not correct, replace the TRS.
(9) With the manual lever in the NEUTRAL posi- tion (the NEUTRAL position is with the manual lever moved two detents forward of the full rearward position), measure the resistance between the Trans- mission Range Sensor MUX and the Transmission Range Sensor 5V Supply pins of the TRS. The resis- tance should be 108.6 ohms. If the resistance is not correct, replace the TRS.
(10) With the manual lever in the DRIVE position (the DRIVE position is with the manual lever moved three detents forward of the full rearward position), measure the resistance between the Transmission Range Sensor MUX and the Transmission Range Sensor 5V Supply pins of the TRS. The resistance should be 59.9 ohms. If the resistance is not correct, replace the TRS.
(11) With the manual lever in the SECOND posi- tion (the SECOND position is with the manual lever moved one detent rearward of the full forward posi- tion), measure the resistance between the Transmis- sion Range Sensor MUX and the Back-up Lamp feed pins of the TRS. The resistance should be 31.9 ohms. If the resistance is not correct, replace the TRS.
(12) With the manual lever in the LOW position (the LOW position is with the manual lever moved to the full forward position), measure the resistance between the Transmission Range Sensor MUX and the Back-up Lamp feed pins of the TRS. The resis- tance should be 13.7 ohms. If the resistance is not correct, replace the TRS.
REMOVAL
(1) Raise vehicle and position drain pan under the
transmission range sensor (TRS).
(2) Move the transmission manual
lever to the manual LOW position. The manual LOW position is with the manual lever in the forward-most detent.
(3) Disengage the wiring connector from the TRS. (4) Remove the two screws holding the TRS to the
TRS mounting bracket.
(5) Remove the TRS (Fig. 244)
from the TRS mounting bracket by pulling it straight out of the bracket.
Fig.244RemoveTransmissionRangeSensor
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET 3 - TRANSMISSION RANGE SENSOR
(6) Loosen the TRS mounting bracket in the trans-
mission case using Adapter 8581 (Fig. 245).
Fig.245LoosentheTRSMountingBracket
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET 3 - ADAPTER 8581
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TRANSMISSION RANGE SENSOR (Continued)AUTOMATIC TRANSMISSION - 48RE
(7) Remove the TRS mounting bracket (Fig. 246)
from the transmission case.
DR
Fig.246RemoveTRSMountingBracket
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET
INSTALLATION
Fig.248RemoveTransmissionRangeSensor
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET 3 - TRANSMISSION RANGE SENSOR
(1) Move the transmission manual shaft lever to
the manual LOW position.
(2) Install the TRS mounting bracket into the transmission case. Using Adapter 8581 (Fig. 247), tighten the mounting bracket to 34 N·m (300 in.lbs.). (3) Install the TRS (Fig. 248) into the mounting
Fig.249TransmissionRangeSensorOperation
1 - NEUTRAL CONTACT 2 - MANUAL LEVER AND SENSOR PLUNGER IN REVERSE POSITION 3 - PARK CONTACT 4 - TRANSMISSION RANGE SENSOR
(6) Move the transmission manual shaft lever to
the PARK position.
lower vehicle.
level.
(7) Connect TRS wiring connector to the TRS and
(8) Refill
the transmission fluid to the correct
Fig.247TightentheTRSMountingBracket
1 - SOLENOID CASE CONNECTOR 2 - TRS MOUNTING BRACKET 3 - ADAPTER 8581
bracket with the wiring connector facing the front of the transmission.
(4) Install the two screws to hold the TRS to the mounting bracket. Tighten the screws to 3.4 N·m (30
in.lbs.).(5) Verify proper sensor operation (Fig. 249).
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AUTOMATIC TRANSMISSION - 48RE
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VALVE BODY DESCRIPTION
(Fig. 252),
The valve body consists of a cast aluminum valve body, a separator plate, and transfer plate. The valve body contains valves and check balls that control fluid delivery to the torque converter clutch, bands, and frictional clutches. The valve body contains the following components (Fig. 251), (Fig. 253), and (Fig. 254): † Regulator valve † Regulator valve throttle pressure plug † Line pressure sleeve † Kickdown valve † Kickdown limit valve † 1-2 shift valve † 1-2 control valve † 2-3 shift valve † 2-3 governor plug † 3-4 shift valve † 3-4 timing valve † 3-4 quick fill valve † 3-4 accumulator † Throttle valve † Throttle pressure plug † Switch valve † Manual valve † Converter clutch lock-up valve † Converter clutch lock-up timing Valve † Shuttle valve † Shuttle valve throttle plug † Boost Valve † 9 check balls By adjusting the spring pressure acting on the reg- transmission line pressure can be
ulator valve, adjusted.
TRANSMISSION TEMPERATURE SENSOR DESCRIPTION
Transmission fluid temperature readings are sup- plied to the transmission control module by the ther- mistor (Fig. 250). The temperature readings are used to control engagement of the fourth gear overdrive clutch, the converter clutch, and governor pressure. Normal resistance value for the thermistor at room temperature is approximately 2000 ohms.
The thermistor is part of the governor pressure sensor assembly and is immersed in transmission fluid at all times.
Fig.250GovernorPressureSensor
1 - GOVERNOR BODY 2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID TEMPERATURE THERMISTOR
OPERATION
The PCM prevents engagement of the converter clutch and overdrive clutch, when fluid temperature is below approximately 10°C (50°F).
If
fluid temperature exceeds 126°C (260°F), the PCM causes a 4-3 downshift and engage the con- verter clutch. Engagement is according to the third gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel illuminates when the shift back to third occurs. The transmission will not allow fourth gear operation until fluid temperature decreases to approximately 110°C (230°F).
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VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
1 - UPPER HOUSING 2 - REGULATOR VALVE 3 - SWITCH VALVE 4 - REGULATOR VALVE SPRING 5 - KICKDOWN VALVE 6 - KICKDOWN DETENT 7 - THROTTLE VALVE AND SPRING
Fig.251UpperHousingControlValveLocations
8 - MANUAL VALVE 9 - 1-2 GOVERNOR PLUG 10 - GOVERNOR PLUG COVER 11 - THROTTLE PLUG 12 - 2-3 GOVERNOR PLUG 13 - SHUTTLE VALVE PRIMARY SPRING
DR VALVE BODY (Continued)
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21 - 447
Fig.252ShuttleandBoostValveLocations
1 - SPRING 2 - RETAINER 3 - BOOST VALVE 4 - BOOST VALVE PLUG 5 - SPRING GUIDES 6 - E-CLIP 7 - SHUTTLE VALVE SECONDARY SPRING
8 - SHUTTLE VALVE COVER 9 - SHUTTLE VALVE 10 - SHUTTLE VALVE PRIMARY SPRING 11 - GOVERNOR PLUG COVER 12 - THROTTLE PLUG 13 - UPPER HOUSING 14 - BOOST VALVE COVER
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VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
Fig.253UpperHousingShiftValveandPressurePlugLocations
1 - UPPER HOUSING 2 - 1-2 SHIFT VALVE AND SPRING 3 - 2-3 SHIFT VALVE AND SPRING 4 - 2-3 THROTTLE PLUG 5 - LIMIT VALVE HOUSING 6 - LIMIT VALVE COVER
7 - LIMIT VALVE AND SPRING 8 - RETAINER 9 - 1-2 SHIFT CONTROL VALVE AND SPRING 10 - PRESSURE PLUG COVER 11 - PLUG SLEEVE 12 - THROTTLE PRESSURE SPRING AND PLUG
DR VALVE BODY (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 449
Fig.254LowerHousingShiftValvesandSprings
1 - 3-4 ACCUMULATOR HOUSING 2 - 3-4 SHIFT VALVE AND SPRING 3 - PLUG 4 - SPRING RETAINER 5 - CONVERTER CLUTCH VALVE AND SPRING 6 - CONVERTER CLUTCH TIMING VALVE AND SPRING 7 - OVERDRIVE SEPARATOR PLATE 8 - CASE CONNECTOR 9 - CONVERTER CLUTCH SOLENOID 10 - OVERDRIVE SOLENOID
11 - TIMING VALVE COVER 12 - PLUG 13 - 3-4 TIMING VALVE AND SPRING 14 - LOWER HOUSING 15 - ACCUMULATOR END PLATE 16 - 3-4 ACCUMULATOR PISTON AND SPRING 17 - E-CLIP 18 - 3-4 QUICK FILL SPRING AND VALVE 19 - SOLENOID GASKET 20 - HARNESS
AUTOMATIC TRANSMISSION - 48RE
21 - 450
VALVE BODY (Continued) OPERATIONNOTE: Refer to the Hydraulic Schematics for a visual aid in determining valve location, operation and design.
CHECK BALLS
CHECK BALL
NUMBER
DESCRIPTION
DR
10
Allows either the manual valve to put line pressure on the 1-2 governor plug or the KD Valve to put WOT line pressure on the 1-2 governor plug. Allows either the Reverse circuit or the 3rd gear circuit to pressurize the front clutch. Allows either the Manual Low circuit from the Manual Valve or the Reverse from the Manual Valve circuit to pressurize the rear servo. Directs line pressure to the spring end of the 2-3 shift valve in either Manual Low or Manual 2nd, forcing the downshift to 2nd gear regardless of governor pressure. Provides a by-pass around the front servo orifice so that the servo can release quickly. Provides a by-pass around the rear clutch orifice so that the clutch can release quickly. Directs reverse line pressure through an orifice to the throttle valve eliminating the extra leakage and insuring that Reverse line pressure pressure will be sufficient. Provides a by-pass around the rear servo orifice so that the servo can release quickly. Allows the lockup clutch to used at WOT in 3rd gear by putting line pressure from the 3-4
Timing Valve on the interlock area of the 2-3 shift valve, thereby preventing a 3rd gear Lock-up to 2nd gear kickdown.REGULATOR VALVE
The pressure regulator valve is needed to control the hydraulic pressure within the system and reduce the amount of heat produced in the fluid. The pres- sure regulator valve is located in the valve body near the manual valve. The pressure regulator valve train controls the maximum pressure in the lines by metering the dumping of fluid back into the sump. Regulated pressure is referred to as “line pressure.” The regulator valve (Fig. 255) has a spring on one end that pushes the valve to the left. This closes a dump (vent) that is used to lower pressure. The clos- ing of the dump will cause the oil pressure to increase. Oil pressure on the opposite end of the valve pushes the valve to the right, opening the dump and lowering oil pressure. The result is spring pressure working against oil pressure to maintain the oil at specific pressures. With the engine run- ning, fluid flows from the pump to the pressure reg- ulator valve, manual valve, and the interconnected circuits. As fluid is sent through passages to the reg- ulator valve, the pressure pushes the valve to the right against the large spring. It is also sent to the reaction areas on the left side of the throttle pressure plug and the line pressure plug. With the gear selec-
tor in the PARK position, fluid recirculates through the regulator and manual valves back to the sump. Meanwhile, the torque converter is filled slowly. In all other gear positions (Fig. 256), fluid flows between two right side lands to the switch valve and torque converter. At low pump speeds, the flow is controlled by the pressure valve groove to reduce pressure to the torque converter. After the torque converter and switch valve fill with fluid, the switch valve becomes the controlling metering device for torque converter pressure. The regulator valve then begins to control the line pressure for the other transmission circuits. The balance of the fluid pres- sure pushing the valve to the right and the spring pressure pushing to the left determines the size of the metering passage at land #2 (land #1 being at the far right of the valve in the diagram). As fluid leaks past the land, it moves into a groove connected to the filter or sump. As the land meters the fluid to the sump, it causes the pressure to reduce and the spring decreases the size of the metering passage. When the size of the metering passage is reduced, the pressure rises again and the size of the land is increased again. Pressure is regulated by this con- stant balance of hydraulic and spring pressure.
DR VALVE BODY (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 451
Fig.255RegulatorValveinParkPosition
Fig.256RegulatorValveinNeutralPosition
21 - 452
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
The metering at land #2 establishes the line pressure throughout the transmission. It is varied according to changes in throttle position and the transmission’s internal condition within a range of 57-94 psi (except in REVERSE) (Fig. 257). The regulated line pressure in REVERSE (Fig. 258) is held at much higher pressures than in the other gear positions: 145-280 psi. The higher pressure for REVERSE is achieved by the man- ual valve blocking the supply of line pressure to the
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reaction area left of land #4. With this pressure blocked, there is less area for pressure to act on to balance the force of the spring on the right. This allows line pres- sure to push the valve train to the right, reducing the amount of fluid returned to the pump’s inlet, increasing line pressure.
Fig.257RegulatorValveinDrivePosition
DR VALVE BODY (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 453
Fig.258RegulatorValveinReversePosition
AUTOMATIC TRANSMISSION - 48RE
21 - 454
VALVE BODY (Continued) KICKDOWN VALVEWhen the throttle valve is as far over to the left as it can go, the maximum line pressure possible will enter the throttle pressure circuit. In this case, throt- tle pressure will equal line pressure. With the kick- down valve (Fig. 259) pushed into the bore as far as it will go, fluid initially flows through the annular groove of the 2-3 shift valve (which will be in the direct drive position to the right).
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After passing the annular groove, the fluid is routed to the spring end of the 2-3 shift valve. Fluid pressure reacting on the area of land #1 overcomes governor pressure, downshifting the 2-3 shift valve into the kickdown, or second gear stage of operation. The valve is held in the kickdown position by throttle pressure routed from a seated check ball (#2). Again, if vehicle speed is low enough, throttle pressure will also push the 1-2 shift valve left to seat its governor plug, and downshift to drive breakaway.
Fig.259KickdownValve-WideOpenThrottle
DR VALVE BODY (Continued) KICKDOWN LIMIT VALVE
The purpose of the limit valve is to prevent a 3-2
downshift at higher speeds when a part-throttle downshift is not desirable. At these higher speeds only a full throttle 3-2 downshift will occur. At low road speeds (Fig. 260) the limit valve does not come into play and does not affect the downshifts. As the vehicle’s speed increases (Fig. 261), the governor pressure also increases. The increased governor pres- sure acts on the reaction area of the bottom land of the limit valve overcoming the spring force trying toAUTOMATIC TRANSMISSION - 48RE
21 - 455
push the valve toward the bottom of its bore. This pushes the valve upward against the spring and bot- toms the valve against the top of the housing. With the valve bottomed against the housing, the throttle pressure supplied to the valve will be closed off by the bottom land of the limit valve. When the supply of throttle pressure has been shut off, the 3-2 part throttle downshift plug becomes inoperative, because no pressure is acting on its reaction area.
Fig.260KickdownLimitValve-LowSpeeds
Fig.261KickdownLimitValve-HighSpeeds
AUTOMATIC TRANSMISSION - 48RE
21 - 456
VALVE BODY (Continued) 1-2 SHIFT VALVEThe 1-2 shift valve assembly (Fig. 262), or mecha- nism, consists of: the 1-2 shift valve, governor plug, and a spring on the end of the valve. After the man- ual valve has been placed into a forward gear range, line pressure is directed to the 1-2 shift valve. As the throttle is depressed, throttle pressure is applied to the right side of the 1-2 shift valve assembly. With throttle pressure applied to the right side of the valve, there is now both spring pressure and throttle pressure acting on the valve, holding it against the governor plug. As the vehicle begins to move and build speed, governor pressure is created and is applied to the left of the valve at the governor plug. When governor pressure builds to a point where it can overcome the combined force of the spring and throttle pressure on the other side of the valve, the valve will begin to move over to the right. As the valve moves to the right, the middle land of the valve will close off the circuit supplying the throttle pres- sure to the right side of the valve. When the throttle
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pressure is closed off, the valve will move even far- ther to the right, allowing line pressure to enter another circuit and energize the front servo, applying the front band (Fig. 263).
right, allowing both upshifts and downshifts.
The governor plug serves a dual purpose: † It allows the shift valves to move either left or † When in a manual selection position, it will be hydraulically “blocked” into position so no upshift can occur.
The physical blocking of the upshift while in the manual “1” position is accomplished by the directing of line pressure between both lands of the governor plug. The line pressure reacts against the larger land of the plug, pushing the plug back against the end plate overcoming governor pressure. With the combi- nation of the line pressure and spring pressure, the valve cannot move, preventing any upshift.
Fig.2621-2ShiftValve-BeforeShift
Fig.2631-2ShiftValve-AfterShift
DR VALVE BODY (Continued) 1-2 SHIFT CONTROL VALVE
It contains a valve with four lands and a spring. It
is used as both a “relay” and “balanced” valve. The valve has two specific operations (Fig. 264): † Aid in quality of the 1-2 upshift. † Aid in the quality and timing of the 3-2 kick- down ranges.
When the manual valve is set to the DRIVE posi- tion and the transmission is in the first or second gear range, 1-2 shift control or “modulated throttle pressure” is supplied to the middle of the accumula- tor piston by the 1-2 shift control valve. During the
AUTOMATIC TRANSMISSION - 48RE
21 - 457
is
1-2 upshift, this pressure is used to control the kick- down servo apply pressure that is needed to apply the kickdown and accumulator pistons. Thus, the 1-2
shift point “cushioned” and the quality is improved. During a WOT kickdown, kickdown pres- sure is applied between the kickdown valve and the 1-2 shift control valve. This additional pressure is directed to the 1-2 shift control’s spring cavity, add- ing to the spring load on the valve. The result of this increased “modulated” throttle pressure is a firmer WOT upshift.Fig.2641-2ShiftControlValve
AUTOMATIC TRANSMISSION - 48RE
21 - 458
VALVE BODY (Continued) 2-3 SHIFT VALVEThe 2-3 shift valve mechanism (Fig. 265) consists of the 2-3 shift valve, governor plug and spring, and a throttle plug. After the 1-2 shift valve has com- pleted its operation and applied the front band, line pressure is directed to the 2-3 shift valve through the connecting passages from the 1-2 shift valve. The line pressure will then dead–end at land #2 until the 2-3
valve is ready to make its shift. Now that the vehicle is in motion and under acceleration, there is throttle pressure being applied to the spring side of the valve and between lands #3 and #4.As vehicle speed increases, governor pressure increases proportionately, until it becomes great enough to overcome the combined throttle and spring pressure on the right side of the valve. Since the throttle pressure end of the 2-3 shift valve is larger in diameter than the 1-2 shift valve, the 2-3 shift will always happen at a greater speed than the 1-2 shift. When this happens, the governor plug is forced against the shift valve moving it to the right. The shift valve causes land #4 to close the passage sup- plying throttle pressure to the 2-3 shift valve. With- out throttle pressure present in the circuit now, the governor plug will push the valve over far enough to bottom the valve in its bore. This allows land #2 to direct line pressure to the front clutch.
After the shift (Fig. 266), line pressure is directed to the release side of the kickdown servo. This releases the front band and applies the front clutch,
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shifting into third gear or direct drive. The rear clutch remains applied, as it has been in the other gears. During a manual “1” or manual “2” gear selection, line pressure is sent between the two lands of the 2-3 governor plug. This line pressure at the governor plug locks the shift valve into the sec- ond gear position, preventing an upshift into direct drive. The theory for the blocking of the valve is the same as that of the 1-2 shift valve.
If the manual “2” or manual “1” gear position is selected from the drive position, the PCM will con- trol the timing of the downshift by targeting for a high governor pressure. When a safe vehicle speed is reached, the PCM will switch to its normal con- trol governor curve and the downshift will occur.
3-4 SHIFT VALVE
The PCM energizes the overdrive solenoid during the 3-4 upshift (Fig. 267). This causes the solenoid check ball to close the vent port allowing line pres- sure from the 2-3 shift valve to act directly on the 3-4 upshift valve. Line pressure on the 3-4 shift valve overcomes valve spring pressure moving the valve to the upshift position (Fig. 268). This action exposes the feed passages to the 3-4 timing valve, 3-4 quick fill valve, 3-4 accumulator, and ultimately to the overdrive piston.
Fig.2652-3ShiftValve-BeforeShift
DR VALVE BODY (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 459
Fig.2662-3ShiftValve-AfterShift
Fig.2673-4ShiftValveBeforeShift
Fig.2683-4ShiftValveAfterShift
3-4 TIMING VALVE
The 3-4 timing valve is moved by line pressure coming through the 3-4 shift valve (Fig. 268) or the converter clutch valve. After the shift, the timing
valve holds the 2-3 shift valve in an upshift position. The purpose is to prevent the 2-3 valve from down- shifting while either the overdrive clutch or converter clutch is applied (Fig. 267).
AUTOMATIC TRANSMISSION - 48RE
21 - 460
VALVE BODY (Continued) 3-4 QUICK FILL VALVEThe 3-4 quick fill valve provides faster engagement of the overdrive clutch during 3-4 upshifts. The valve temporarily bypasses the clutch piston feed orifice at the start of a 3-4 upshift (Fig. 267). This exposes a larger passage into the piston retainer resulting in a much faster clutch fill and apply sequence. The quick fill valve does not bypass the regular clutch feed ori- fice throughout the 3-4 upshift. Instead, once a pre- determined pressure develops within the clutch, the valve closes the bypass (Fig. 268). Clutch fill is then completed through the regular feed orifice.
THROTTLE VALVE
In all gear positions the throttle valve (Fig. 269) is being supplied with line pressure. The throttle valve meters and reduces the line pressure that now becomes throttle pressure. The throttle valve is moved by a spring and the kickdown valve, which is mechanically connected to the throttle. The larger the throttle opening, the higher the throttle pressure (to a maximum of line pressure). The smaller the throttle opening, the lower the throttle pressure (to a minimum of zero at idle). As engine speed increases, the increase in pump speed increases pump output. The increase in pressure and volume must be regu- lated to maintain the balance within the transmis- sion. To do this, throttle pressure is routed to the reaction area on the right side of the throttle pres- sure plug (in the regulator valve).
The higher engine speed and line pressure would open the vent too far and reduce line pressure too much. Throttle pressure, which increases with engine
DR
speed (throttle opening), is used to oppose the move- ment of the pressure valve to help control the meter- ing passage at the vent. The throttle pressure is combined with spring pressure to reduce the force of the throttle pressure plug on the pressure valve. The larger spring at the right closes the regulator valve passage and maintains or increases line pressure. The increased line pressure works against the reac- tion area of the line pressure plug and the reaction area left of land #3 simultaneously moves the regu- lator valve train to the right and controls the meter- ing passage.
The kickdown valve, along with the throttle valve, serve to delay upshifts until the correct vehicle speed has been reached. It also controls downshifts upon driver demand, or increased engine load. If these valves were not in place, the shift points would be at the same speed for all throttle positions. The kick- down valve is actuated by a cam connected to the throttle. This is accomplished through either a link- age or a cable. The cam forces the kickdown valve toward the throttle valve compressing the spring between them and moving the throttle valve. As the throttle valve land starts to uncover its port, line pressure is “metered” out into the circuits and viewed as throttle pressure. This increased throttle pressure is metered out into the circuits it is applied to: the 1-2 and 2-3 shift valves. When the throttle pressure is high enough, a 3-2 downshift will occur. If the vehicle speed is low enough, a 2-1 downshift will occur.
Fig.269ThrottleValve
AUTOMATIC TRANSMISSION - 48RE
21 - 461
DR VALVE BODY (Continued) SWITCH VALVE
When the transmission is in Drive Second before the TCC application occurs (Fig. 270), the pressure regulator valve is supplying torque converter pres- sure to the switch valve. The switch valve directs this pressure through the transmission input shaft, into the converter, through the converter, back out between the input shaft and the reaction shaft, and back up to the switch valve. From the switch valve, the fluid pressure is directed to the transmission cooler, and lubrication pressure returns from the cooler to lubricate different portions of the transmis- sion.
Fig.270SwitchValve-TorqueConverterUnlocked
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21 - 462
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
Once the TCC control valve has moved to the right (Fig. 271), line pressure is directed to the tip of the switch valve, forcing the valve to the right. The switch valve now vents oil from the front of the pis- ton in the torque converter, and supplies line pres- sure to the (rear) apply side of the torque converter piston. This pressure differential causes the piston to apply against the friction material, cutting off any further flow of line pressure oil. After the switch valve is shuttled right allowing line pressure to engage the TCC, torque converter pressure is directed past the switch valve into the transmission cooler and lubrication circuits.
Fig.271SwitchValve-TorqueConverterLocked
DR VALVE BODY (Continued) MANUAL VALVE
The manual valve (Fig. 272) is a relay valve. The purpose of the manual valve is to direct fluid to the correct circuit needed for a specific gear or driving range. The manual valve, as the name implies, is manually operated by the driver with a lever located on the side of the valve body. The valve is connected mechanically by either a cable or linkage to the gear- shift mechanism. The valve is held in each of its positions by a spring-loaded roller or ball that engages the “roostercomb” of the manual valve lever.
CONVERTER CLUTCH LOCK-UP VALVE
The torque converter clutch (TCC) lock-up valve controls the back (ON) side of the torque converter clutch. When the PCM energizes the TCC solenoid to engage the converter clutch piston, pressure is applied to the TCC lock-up valve which moves to the right and applies pressure to the torque converter clutch.
CONVERTER CLUTCH LOCK-UP TIMING VALVE
The torque converter clutch (TCC) lock-up timing valve is there to block any 4-3 downshift until the TCC is completely unlocked and the clutch is disen- gaged.
AUTOMATIC TRANSMISSION - 48RE
21 - 463
SHUTTLE VALVE
The assembly is contained in a bore in the valve body above the shift valves. When the manual valve is positioned in the Drive range, throttle pressure acts on the throttle plug of the shuttle valve (Fig. 264) to move it against a spring, increasing the spring force on the shuttle valve. During a part or full throttle 1-2 upshift, the throttle plug is bottomed by throttle pressure, holding the shuttle valve to the right against governor pressure, and opening a by–pass circuit. The shuttle valve controls the qual- ity of the kickdown shift by restricting the rate of fluid discharge from the front clutch and servo release circuits. During a 3-2 kickdown, fluid dis- charges through the shuttle by-pass circuit. When the shuttle valve closes the by-pass circuit, fluid dis- charge is restricted and controlled for the application of the front band. During a 2-3 “lift foot” upshift, the shuttle valve by-passes the restriction to allow full fluid flow through the by-pass groove for a faster release of the band.
Fig.272ManualValve
AUTOMATIC TRANSMISSION - 48RE
21 - 464
VALVE BODY (Continued) BOOST VALVEThe boost valve (Fig. 273) provides increased fluid apply pressure to the overdrive clutch during 3-4
upshifts (Fig. 274), and when accelerating in fourth gear. The boost valve also serves to increase line pressure during torque converter lock-up.Fig.273BoostValveBeforeLock-up
DR
REMOVAL
The valve body can be removed for service without
having to remove the transmission assembly.
The valve body can be disassembled for cleaning
and inspection of the individual components.
The only replaceable valve body components are: † Manual lever. † Manual lever washer, seal, E-clip, and shaft seal. † Manual lever detent ball. † Throttle lever. † Fluid filter. † Pressure adjusting screw bracket. † Governor pressure solenoid. † Governor pressure sensor (includes transmission † Converter and harness. † Governor housing gasket. † Solenoid case connector O-rings. (1) Shift transmission into NEUTRAL. (2) Raise vehicle. (3) Remove gearshift and throttle levers from shaft
clutch/overdrive solenoid assembly
temperature thermistor).
of valve body manual lever.
(4) Disconnect wires at solenoid case connector
(Fig. 275).
(5) Remove the transmission range sensor. (6) Position drain pan under transmission oil pan. (7) Remove transmission oil pan and gasket. (8) Remove fluid filter from valve body. (9) Remove bolts attaching valve body to transmis-
sion case.
(10) Lower valve body enough to remove accumu-
lator piston and springs.
(11) Work manual lever shaft and electrical con-
nector out of transmission case.
Fig.274BoostValveAfterLock-up
Fig.275TransmissionCaseConnector
1 - SOLENOID CASE CONNECTOR 2 - TRANSMISSION RANGE SENSOR
DR VALVE BODY (Continued)
(12) Lower valve body, rotate valve body away from case, pull park rod out of sprag, and remove valve body (Fig. 276).
AUTOMATIC TRANSMISSION - 48RE
21 - 465
(5) Remove governor pressure solenoid by pulling it straight out of bore in governor body. Remove and discard solenoid O-rings if worn, cut, or torn.
(6) Remove small shoulder bolt that secures sole- noid harness case connector to 3-4 accumulator hous- ing (Fig. 277). Retain shoulder bolt. Either tape it to harness or thread it back into accumulator housing after connector removal.
(7) Unhook overdrive/converter solenoid harness
from 3-4 accumulator cover plate (Fig. 278).
Fig.277SolenoidHarnessCaseConnector
ShoulderBolt
1 - SOLENOID HARNESS CASE CONNECTOR 2 - 3-4 ACCUMULATOR HOUSING
Fig.276ValveBody
1 - VALVE BODY 2 - WIRE HARNESS 3 - PARK ROD 4 - GOVERNOR PRESSURE SOLENOID 5 - GOVERNOR PRESSURE SENSOR
DISASSEMBLY
CAUTION: Do not clamp any valve body component in a vise. This practice can damage the component resulting in unsatisfactory operation after assembly and installation. Do not use pliers to remove any of the valves, plugs or springs and do not force any of the components out or into place. The valves and valve body housings will be damaged if force is used. Tag or mark the valve body springs for refer- ence as they are removed. Do not allow them to become intermixed.
(1) Disconnect wires from governor pressure sen-
sor and solenoid.
(2) Remove screws attaching governor body and
retainer plate to transfer plate.
(3) Remove retainer plate, governor body and gas-
ket from transfer plate.
(4) Remove governor pressure sensor from gover-
nor body.
Fig.278SolenoidHarnessRouting
1 - OVERDRIVE/CONVERTER SOLENOID WIRE HARNESS 2 - 3-4 ACCUMULATOR COVER PLATE
21 - 466
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(8) Turn valve body over and remove screws that attach overdrive/converter solenoid assembly to valve body (Fig. 279).
(9) Remove solenoid and harness assembly from
valve body (Fig. 280).
(10) Remove boost valve cover (Fig. 281). (11) Remove boost valve retainer, valve spring and
boost valve (Fig. 282).
Fig.281BoostValveCoverLocation
1 - BOOST VALVE HOUSING AND COVER 2 - BOOST VALVE TUBE
Fig.279SolenoidAssemblyScrews
1 - OVERDRIVE/CONVERTER CLUTCH SOLENOID ASSEMBLY 2 - HARNESS
Fig.282BoostValveComponents
1 - SPRING AND VALVE RETAINER 2 - COVER SCREWS 3 - BOOST VALVE COVER 4 - BOOST VALVE PLUG 5 - BOOST VALVE 6 - BOOST VALVE SPRING
(12) Secure detent ball and spring with Retainer
Tool 6583 (Fig. 283).
Fig.280SolenoidAssembly
1 - GOVERNOR SOLENOID WIRES 2 - CONVERTER CLUTCH SOLENOID 3 - SOLENOID SCREWS 4 - GOVERNOR SENSOR WIRES 5 - OVERDRIVE SOLENOID 6 - HARNESS 7 - CASE CONNECTOR
Fig.283DetentBallSpring
1 - SPECIAL TOOL 6583 POSITIONED ON DETENT HOUSING
DR VALVE BODY (Continued)
(13) Remove park rod E-clip and separate rod from
manual lever (Fig. 284).
(14) Remove E-clip and washer that retains throt-
tle lever shaft in manual lever (Fig. 285).
AUTOMATIC TRANSMISSION - 48RE
21 - 467
(15) Remove manual lever and throttle lever (Fig. 286). Rotate and lift manual lever off valve body and throttle lever shaft. Then slide throttle lever out of valve body.
(16) Position pencil magnet next to detent housing to catch detent ball and spring. Then carefully remove Retainer Tool 6583 and remove detent ball and spring (Fig. 287).
Fig.284ParkRod
1 - MANUAL LEVER 2 - E-CLIP 3 - PARK ROD
Fig.286ManualAndThrottleLever
1 - PARK ROD 2 - MANUAL LEVER ASSEMBLY 3 - THROTTLE LEVER
Fig.285ThrottleLeverE-ClipAndWasher
1 - THROTTLE LEVER SHAFT 2 - E-CLIP AND WASHER 3 - MANUAL SHAFT
Fig.287DetentBallAndSpring
1 - DETENT HOUSING 2 - DETENT SPRING 3 - DETENT BALL 4 - PENCIL MAGNET
21 - 468
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
(17) Remove screws attaching pressure adjusting screw bracket to valve body and transfer plate (Fig. 288). Hold bracket firmly against spring tension while removing last screw.
DR
(18) Remove adjusting screw bracket, line pressure adjusting screw, pressure regulator valve spring and switch valve spring (Fig. 289). Do not remove throttle pressure adjusting screw from bracket and do not disturb setting of either adjusting screw during removal.
Fig.288AdjustingScrewBracketFastener
1 - T25 TORX™ BIT 2 - REMOVE THESE SCREWS FIRST 3 - BRACKET 4 - BRACKET 5 - REMOVE THIS SCREW LAST
Fig.289AdjustingScrewBracket
1 - SWITCH VALVE SPRING 2 - LINE PRESSURE SCREW 3 - THROTTLE PRESSURE ADJUSTING SCREW 4 - ADJUSTING SCREW BRACKET 5 - PRESSURE REGULATOR VALVE SPRING
(19) Turn upper housing over and remove switch valve, regulator valve and spring, and manual valve (Fig. 290).
(20) Remove kickdown detent, kickdown valve, and
throttle valve and spring (Fig. 290).
(21) Loosen left-side 3-4 accumulator housing attaching screw about 2-3 threads. Then remove cen- ter and right-side housing attaching screws (Fig. 291).
(22) Carefully rotate 3-4 accumulator housing upward and remove 3-4 shift valve spring and con- verter clutch valve plug and spring (Fig. 292).
DR VALVE BODY (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 469
1 - UPPER HOUSING 2 - REGULATOR VALVE 3 - SWITCH VALVE 4 - REGULATOR VALVE SPRING 5 - KICKDOWN VALVE 6 - KICKDOWN DETENT 7 - THROTTLE VALVE AND SPRING
Fig.290UpperHousingControlValveLocations
8 - MANUAL VALVE 9 - 1-2 GOVERNOR PLUG 10 - GOVERNOR PLUG COVER 11 - THROTTLE PLUG 12 - 2-3 GOVERNOR PLUG 13 - SHUTTLE VALVE PRIMARY SPRING
Fig.291AccumulatorHousingScrewLocations
1 - LOOSEN THIS SCREW 2 - REMOVE THESE SCREWS 3 - 3-4 ACCUMULATOR HOUSING
Fig.2923-4ShiftAndConverterClutchValve
SpringsandPlug
1 - ACCUMULATOR HOUSING 2 - CONVERTER CLUTCH VALVE SPRING 3 - CLUTCH VALVE PLUG 4 - 3-4 SHIFT VALVE SPRING
21 - 470
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(23) Remove left-side screw and remove 3-4 accu-
mulator housing from valve body (Fig. 293).
(24) Bend back tabs on boost valve tube brace (Fig.
294).
(26) Turn valve body over so lower housing is fac- ing upward (Fig. 296). In this position, the two check balls in upper housing will remain in place and not fall out when lower housing and separator plate are removed.
(27) Remove screws attaching valve body lower housing to upper housing and transfer plate (Fig. 296). Note position of boost valve tube brace for assembly reference.
(28) Remove lower housing and overdrive separa-
tor plate from transfer plate (Fig. 296).
Fig.293AccumulatorHousing,ValveSprings,and
Plug
1 - 3-4 SHIFT VALVE SPRING 2 - CONVERTER CLUTCH VALVE SPRING AND PLUG 3 - 3-4 ACCUMULATOR HOUSING
Fig.295BoostValveTube
1 - BOOST VALVE TUBE 2 - LOWER HOUSING 3 - DISENGAGE THIS END OF TUBE FIRST 4 - UPPER HOUSING
Fig.294BoostValveTubeBrace
1 - BOOST VALVE TUBE 2 - TUBE BRACE (DOUBLE TAB)
(25) Remove boost valve connecting tube (Fig. 295). Disengage tube from upper housing port first. Then rock opposite end of tube back and forth to work it out of lower housing.
CAUTION: Do not use tools to loosen or pry the connecting tube out of the valve body housings. Loosen and remove the tube by hand only.
Fig.296LowerHousing
1 - LOWER HOUSING 2 - OVERDRIVE SEPARATOR PLATE 3 - TRANSFER PLATE AND UPPER HOUSING
AUTOMATIC TRANSMISSION - 48RE
21 - 471
(33) Remove rear clutch and rear servo check balls location for
from transfer plate. Note check ball assembly reference (Fig. 300).
Fig.299UpperHousingSeparatorPlate
1 - TRANSFER PLATE 2 - UPPER HOUSING SEPARATOR PLATE 3 - FILTER SCREEN 4 - BRACE
Fig.300RearClutchandRearServoCheckBall
Locations
1 - REAR CLUTCH CHECK BALL 2 - REAR SERVO CHECK BALL 3 - TRANSFER PLATE
DR VALVE BODY (Continued)
(29) Remove the Number 10 check ball from the transfer plate (Fig. 297). The check ball is approxi- mately 4.8 mm (3/16 in.) in diameter.
(30) Remove transfer plate from upper housing
(Fig. 298).
(31) Turn transfer plate over so upper housing sep-
arator plate is facing upward.
(32) Remove upper housing separator plate from transfer plate (Fig. 299). Note position of filter in separator plate for assembly reference.
Fig.297Number10CheckBall
1 - NUMBER 10 CHECK BALL (3/169)
Fig.298TransferPlate
1 - UPPER HOUSING 2 - TRANSFER PLATE
AUTOMATIC TRANSMISSION - 48RE
21 - 472
VALVE BODY (Continued) VALVE BODY UPPER HOUSINGDR
Fig.302ShuttleValveE-ClipAndSecondarySpring 1 - E-CLIP 2 - SECONDARY SPRING AND GUIDES 3 - SHUTTLE VALVE
(1) Note location of check balls in valve body upper housing (Fig. 301). Then remove the one large diam- eter and the five smaller diameter check balls.
(2) Remove governor plug and shuttle valve covers
(Fig. 303).
(3) Remove E-clip that secures shuttle valve sec-
ondary spring on valve stem (Fig. 302).
(4) Remove throttle plug, primary spring, shuttle valve, secondary spring, and spring guides (Fig. 303). (5) Remove boost valve retainer, spring and valve
if not previously removed.
(6) Remove throttle plug and 1-2 and 2-3 governor
plugs (Fig. 290).
(7) Turn upper housing around and remove limit
valve and shift valve covers (Fig. 304).
(8) Remove limit valve housing. Then remove retainer, spring, limit valve, and 2-3 throttle plug from limit valve housing (Fig. 304).
(9) Remove 1-2 shift control valve and spring (Fig.
304).
(10) Remove 1-2 shift valve and spring (Fig. 304). (11) Remove 2-3 shift valve and spring from valve
body (Fig. 304).
(12) Remove pressure plug cover (Fig. 304). (13) Remove line pressure sleeve, throttle pressure
plug and spring (Fig. 304).
Fig.301CheckBallLocationsInUpperHousing
1 - SMALL DIAMETER CHECK BALLS (5) 2 - LARGE DIAMETER CHECK BALL (1)
DR VALVE BODY (Continued)
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Fig.303ShuttleandBoostValveLocation
1 - SPRING 2 - RETAINER 3 - BOOST VALVE 4 - BOOST VALVE PLUG 5 - SPRING GUIDES 6 - E-CLIP 7 - SHUTTLE VALVE SECONDARY SPRING
8 - SHUTTLE VALVE COVER 9 - SHUTTLE VALVE 10 - SHUTTLE VALVE PRIMARY SPRING 11 - GOVERNOR PLUG COVER 12 - THROTTLE PLUG 13 - UPPER HOUSING 14 - BOOST VALVE COVER
21 - 474
VALVE BODY (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
Fig.304UpperHousingShiftValveandPressurePlugLocations
1 - UPPER HOUSING 2 - 1-2 SHIFT VALVE AND SPRING 3 - 2-3 SHIFT VALVE AND SPRING 4 - 2-3 THROTTLE PLUG 5 - LIMIT VALVE HOUSING 6 - LIMIT VALVE COVER
7 - LIMIT VALVE AND SPRING 8 - RETAINER 9 - 1-2 SHIFT CONTROL VALVE AND SPRING 10 - PRESSURE PLUG COVER 11 - PLUG SLEEVE 12 - THROTTLE PRESSURE SPRING AND PLUG
AUTOMATIC TRANSMISSION - 48RE
21 - 475
DR VALVE BODY (Continued) VALVE BODY LOWER HOUSING (1) Remove timing valve cover. (2) Remove 3-4 timing valve and spring. (3) Remove 3-4 quick fill valve, spring and plug. (4) Remove 3-4 shift valve and spring. (5) Remove converter clutch valve, spring and plug
(6) Remove converter clutch timing valve, retainer
(Fig. 305).
and valve spring.
Fig.305LowerHousingShiftValvesandSprings
1 - 3-4 ACCUMULATOR HOUSING 2 - 3-4 SHIFT VALVE AND SPRING 3 - PLUG 4 - SPRING RETAINER 5 - CONVERTER CLUTCH VALVE AND SPRING 6 - CONVERTER CLUTCH TIMING VALVE AND SPRING 7 - OVERDRIVE SEPARATOR PLATE 8 - CASE CONNECTOR 9 - CONVERTER CLUTCH SOLENOID 10 - OVERDRIVE SOLENOID
11 - TIMING VALVE COVER 12 - PLUG 13 - 3-4 TIMING VALVE AND SPRING 14 - LOWER HOUSING 15 - ACCUMULATOR END PLATE 16 - 3-4 ACCUMULATOR PISTON AND SPRING 17 - E-CLIP 18 - 3-4 QUICK FILL SPRING AND VALVE 19 - SOLENOID GASKET 20 - HARNESS
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VALVE BODY (Continued) 3-4 ACCUMULATOR HOUSING(1) Remove end plate from housing. (2) Remove piston spring. (3) Remove piston. Remove and discard piston
seals (Fig. 306).
DR
part has deformed, broken, etc.).
sustained
physical
damage
(dented,
CAUTION: Do not turn the small screw at the end of the solenoid valve for any reason. Turning the screw in either direction will ruin solenoid calibra- tion and result in solenoid failure. In addition, the filter on the solenoid valve is NOT serviceable. Do not try to remove the filter as this will damage the valve housing.
INSPECTION
Inspect the throttle and manual valve levers and shafts. Do not attempt to straighten a bent shaft or correct a loose lever. Replace these components if worn, bent, loose or damaged in any way.
Inspect all of the valve body mating surfaces for scratches, nicks, burrs, or distortion. Use a straight- edge to check surface flatness. Minor scratches may be removed with crocus cloth using only very light pressure.
Minor distortion of a valve body mating surface may be corrected by smoothing the surface with a sheet of crocus cloth. Position the crocus cloth on a surface plate, sheet of plate glass or equally flat sur- face. If distortion is severe or any surfaces are heavily scored, the valve body will have to be replaced.
CAUTION: Many of the valves and plugs, such as the throttle valve, shuttle valve plug, 1-2 shift valve and 1-2 governor plug, are made of coated alumi- num. Aluminum components are identified by the dark color of the special coating applied to the sur- face (or by testing with a magnet). Do not sand alu- minum valves or plugs under any circumstances. This practice could damage the special coating causing the valves/plugs to stick and bind.
Inspect the valves and plugs for scratches, burrs, nicks, or scores. Minor surface scratches on steel valves and plugs can be removed with crocus cloth but do not round off the edges of the valve or plug lands.Maintaining sharpness of these edges is vitally important. The edges prevent foreign matter from lodging between the valves and plugs and the bore.
Inspect all the valve and plug bores in the valve body. Use a penlight to view the bore interiors. Replace the valve body if any bores are distorted or scored. Inspect all of the valve body springs. The springs must be free of distortion, warpage or broken coils.
Fig.3063-4AccumulatorandHousing
1 - ACCUMULATOR PISTON 2 - 3-4 ACCUMULATOR HOUSING 3 - TEFLON SEALS 4 - PISTON SPRING 5 - COVER PLATE AND SCREWS
CLEANING
Clean the valve housings, valves, plugs, springs, and separator plates with a standard parts cleaning solution only. Do not use gasoline, kerosene, or any type of caustic solution.
Do not immerse any of the electrical components in cleaning solution. Clean the governor solenoid and sensor and the dual solenoid and harness assembly by wiping them off with dry shop towels only.
Dry all except the electrical parts with compressed air. Make sure all passages are clean and free from obstructions. Do not use rags or shop towels to dry or wipe off valve body components. Lint from these materials can stick to valve body parts, interfere with valve operation, and clog filters and fluid passages.
Wipe the governor pressure sensor and solenoid valve with dry, lint free shop towels only. The O-rings on the sensor and solenoid valve are the only service- able components. Be sure the vent ports in the sole- noid valve are open and not blocked by dirt or debris. Replace the valve and/or sensor only when DRB scan tool diagnosis indicates this is necessary. Or, if either
AUTOMATIC TRANSMISSION - 48RE
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