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ing.
(17) Position Guide Ring 8114-1 on outer edge of
overdrive piston retainer.
overdrive piston retainer.
(18) Position Seal Guide 8114-3 on inner edge of
(19) Install overdrive piston in overdrive piston retainer by: aligning locating lugs on overdrive piston to the two mating holes in retainer.
(a) Aligning locating lugs on overdrive piston to
the two mating holes in retainer.
(b) Lubricate overdrive piston seals with Mopart
Door Ease, or equivalent.
inside Guide Ring 8114-1.
(c) Install piston over Seal Guide 8114-3 and
(d) Push overdrive piston into position in
retainer.
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DR PISTONS (Continued) PRESSURE
Pressure (Fig. 194)
is nothing more than force (lbs.) divided by area (in or ft.), or force per unit area. Given a 100 lb. block and an area of 100 sq. in. on the floor, the pressure exerted by the block is: 100
lbs. 100 in or 1 pound per square inch, or PSI as it is commonly referred to.Fig.195PressureonaConfinedFluid
FORCE MULTIPLICATION
Using the 10 PSI example used in the illustration (Fig. 196), a force of 1000 lbs. can be moved with a force of only 100 lbs. The secret of force multiplica- tion in hydraulic systems is the total fluid contact area employed. The illustration, (Fig. 196), shows an area that is ten times larger than the original area. The pressure created with the smaller 100 lb. input is 10 PSI. The concept “pressure is the same every- where” means that the pressure underneath the larger piston is also 10 PSI. Pressure is equal to the force applied divided by the contact area. Therefore, by means of simple algebra, the output force may be found. This concept is extremely important, as it is also used in the design and operation of all shift valves and limiting valves in the valve body, as well as the pistons, of the transmission, which activate the clutches and bands. It is nothing more than using a difference of area to create a difference in pressure to move an object.
Fig.196ForceMultiplication
Fig.194ForceandPressureRelationship
PRESSURE ON A CONFINED FLUID
Pressure is exerted on a confined fluid (Fig. 195) by applying a force to some given area in contact with the fluid. A good example of this is a cylinder filled with fluid and equipped with a piston that is closely fitted to the cylinder wall. If a force is applied to the piston, pressure will be developed in the fluid. Of course, no pressure will be created if the fluid is not confined. It will simply “leak” past the piston. There must be a resistance to flow in order to create pressure. Piston sealing is extremely important in hydraulic operation. Several kinds of seals are used to accomplish this within a transmission. These include but are not limited to O-rings, D-rings, lip seals, sealing rings, or extremely close tolerances between the piston and the cylinder wall. The force exerted is down- ward (gravity), however, the principle remains the same no matter which direction is taken. The pressure created in the fluid is equal to the force applied, divided by the piston area. If the force is 100 lbs., and the piston area is 10 sq. in., then the pressure created equals 10 PSI. Another interpretation of Pascal’s Law is that regardless of container shape or size, the pressure will be main- tained throughout, as long as the fluid is confined. In other words, the pressure in the fluid is the same every- where within the container.
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PISTONS (Continued) PISTON TRAVELThe relationship between hydraulic lever and a mechanical lever is the same. With a mechanical lever it’s a weight-to-distance output rather than a pressure-to-area output. Using the same forces and areas as in the previous example, the smaller piston (Fig. 197) has to move ten times the distance required to move the larger piston one inch. There- fore, for every inch the larger piston moves, the smaller piston moves ten inches. This principle is true in other instances also. A common garage floor jack is a good example. To raise a car weighing 2000
lbs., an effort of only 100 lbs. may be required. For every inch the car moves upward, the input piston at the jack handle must move 20 inches downward.DR
Fig.198PlanetaryGearset
1 - ANNULUS GEAR 2 - SUN GEAR 3 - PLANET CARRIER 4 - PLANET PINIONS (4)
† The sun gear which is at the center of the sys- tem.† The planet carrier with planet pinion gears which are free to rotate on their own shafts and are in mesh with the sun gear. † The annulus gear, which rotates around and is
in mesh with the planet pinion gears.
NOTE: The number of pinion gears does not affect the gear ratio, only the duty rating.
OPERATION
tions must be met for power to be able to flow:
With any given planetary gearset, several condi- † One member must be held. † Another member must be driven or used as an input.† The third member may be used as an output for power flow. † For direct drive to occur, two gear members in
the front planetary gearset must be driven.
NOTE: Gear ratios are dependent on the number of teeth on the annulus and sun gears.
Fig.197PistonTravel
PLANETARY GEARTRAIN/ OUTPUT SHAFT DESCRIPTION
The planetary gearsets (Fig. 198) are designated as the front, rear, and overdrive planetary gear assem- blies and located in such order. A simple planetary gearset consists of three main members:
DR PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued) DISASSEMBLY
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(1) Remove planetary snap-ring from intermediate shaft (Fig. 199). Discard snap-ring as it is not reus- able.
(2) Remove front planetary gear and front annulus
gear as assembly (Fig. 200).
(3) Remove
front planetary gear and thrust washer from front annulus gear (Fig. 201). Note thrust washer position for assembly reference.
(4) Remove tabbed thrust washer from driving shell (Fig. 202). Note washer position for assembly reference.
Fig.201DisassemblingFrontPlanetaryAnd
AnnulusGears
1 - FRONT PLANETARY GEAR 2 - TABBED THRUST WASHER 3 - FRONT ANNULUS GEAR 4 - TORLON BUSHING
Fig.202DrivingShellThrustWasherRemoval
1 - DRIVING SHELL 2 - TABBED THRUST WASHER 3 - SUN GEAR
Fig.199RemovingPlanetarySnap-Ring
1 - PLANETARY SNAP-RING
Fig.200RemovingFrontPlanetaryAndAnnulus
Gears
1 - DRIVING SHELL 2 - FRONT ANNULUS GEAR 3 - FRONT PLANETARY GEAR
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PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued)AUTOMATIC TRANSMISSION - 48RE
(5) Remove sun gear and driving shell as assembly
(Fig. 203).
DR
Fig.203SunGearAndDrivingShellRemoval
1 - INTERMEDIATE SHAFT 2 - DRIVING SHELL 3 - SUN GEAR
Fig.205RearPlanetaryAndAnnulusGearRemoval 1 - INTERMEDIATE SHAFT 2 - REAR ANNULUS GEAR 3 - REAR PLANETARY GEAR
(6) Remove tabbed thrust washer from rear plane- tary gear (Fig. 204). Note washer position on gear for assembly reference.
(7) Remove rear planetary gear and rear annulus
gear from intermediate shaft (Fig. 205).
(8) Remove thrust washer from rear planetary
gear (Fig. 206).
Fig.206RearAnnulusThrustWasherRemoval
1 - REAR ANNULUS GEAR 2 - THRUST WASHER
planetary thrust plates and the tabbed thrust wash- ers if cracked, scored or worn.
Inspect the machined surfaces of the intermediate shaft. Be sure the oil passages are open and clear. Replace the shaft if scored, pitted, or damaged.
Inspect the sun gear and driving shell. If either component is worn or damaged, remove the sun gear rear retaining ring and separate the sun gear and thrust plate from the driving shell. Then replace the necessary component.
Replace the sun gear as an assembly if the gear teeth are chipped or worn. Also replace the gear as an assem- bly if the bushings are scored or worn. The sun gear bushings are not serviceable. Replace the thrust plate if worn, or severely scored. Replace the driving shell if dis- torted, cracked, or damaged in any way.
Replace all snap-rings during geartrain assembly.
Reusing snap-rings is not recommended.
Fig.204RearPlanetaryThrustWasherRemoval
1 - SUN GEAR 2 - REAR PLANETARY THRUST WASHER 3 - DRIVING SHELL
INSPECTION
Inspect the planetary gear sets and annulus gears. The planetary pinions, shafts, washers, and retaining pins are serviceable. However, if a pinion carrier is damaged, the entire planetary gear set must be replaced as an assembly.
Replace the annulus gears if the teeth are chipped, broken, or worn, or the gear is cracked. Replace the
DR PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued) ASSEMBLY
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(4) Install thrust washer to rear planetary gear (Fig. 209) using petroleum jelly. Be sure washer is seated against corner witht teh tabs completely in the locating holes.
(1) Lubricate sun gear and planetary gears with transmission fluid during assembly. Use petroleum jelly to lubricate intermediate shaft bushing surfaces, thrust washers and thrust plates and to hold these parts in place during assembly.
(2) Install front snap-ring on sun gear and install gear in driving shell. Then install thrust plate over sun gear and against rear side of driving shell (Fig. 207). Install rear snap-ring to secure sun gear and thrust plate in driving shell. Note that the large ID chamfer on the sun gear goes forward.
(3) Install rear annulus gear on intermediate shaft
(Fig. 208).
Fig.209InstallingRearAnnulusThrustWasher
1 - REAR ANNULUS GEAR 2 - THRUST WASHER
(5) Install rear planetary gear in rear annulus gear (Fig. 210). Be sure planetary carrier is seated against annulus gear.
Fig.210InstallingRearPlanetaryGear
1 - REAR ANNULUS GEAR 2 - REAR PLANETARY GEAR
Fig.207SunGearInstallation
1 - DRIVING SHELL 2 - SUN GEAR 3 - THRUST PLATE 4 - SUN GEAR REAR RETAINING RING
Fig.208InstallingRearAnnulusGearOn
IntermediateShaft
1 - REAR ANNULUS GEAR 2 - OUTPUT SHAFT
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PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(10) Install tabbed thrust washer on front plane- tary gear (Fig. 214). Seat washer tabs in matching
(6) Install tabbed thrust washer on front face of rear planetary gear (Fig. 211). Seat washer tabs in matching slots in face of gear carrier. Use extra petroleum jelly to hold washer in place if desired.
(7) Lubricate sun gear bushings with petroleum
jelly or transmission fluid.
(8) Install sun gear and driving shell on interme- diate shaft (Fig. 212). Seat shell against rear plane- tary gear. Verify that thrust washer on planetary gear was not displaced during installation.
(9) Install tabbed thrust washer in driving shell (Fig. 213), be sure washer tabs are seated in tab slots of driving shell. Use extra petroleum jelly to hold washer in place if desired.
Fig.213InstallingDrivingShellThrustWasher
1 - TAB SLOTS (3) 2 - DRIVING SHELL 3 - TABBED THRUST WASHER
Fig.211InstallingRearPlanetaryThrustWasher
1 - REAR PLANETARY GEAR 2 - TABBED THRUST WASHER
Fig.212InstallingSunGearAndDrivingShell
1 - OUTPUT SHAFT 2 - DRIVING SHELL 3 - REAR PLANETARY GEAR 4 - OUTPUT SHAFT 5 - SUN GEAR
Fig.214InstallingThrustWasherOnFront
PlanetaryGear
1 - TABBED THRUST WASHER 2 - FRONT PLANETARY GEAR
DR PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued)
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slots in face of gear carrier. Use extra petroleum jelly to hold washer in place if desired.
(11) Install the torlon bushing onto the front plan-
etary carrier hub.
(12) Install front annulus gear over and onto front planetary gear (Fig. 215). Be sure gears are fully meshed and seated.
(13) Install
front planetary and annulus gear assembly (Fig. 216). Hold gears together and slide them onto shaft. Be sure planetary pinions are seated on sun gear and that planetary carrier is seated on intermediate shaft.
(14) Place geartrain in upright position. Rotate gears to be sure all components are seated and prop- erly assembled. Snap-ring groove at forward end of intermediate shaft will be completely exposed when components are assembled correctly.
(15) Install new planetary snap-ring in groove at
end of intermediate shaft (Fig. 217).
(16) Turn planetary geartrain over. Position wood block under front end of intermediate shaft and sup- port geartrain on shaft. Be sure all geartrain parts have moved forward against planetary snap-ring. This is important for accurate end play check.
Fig.216InstallingFrontPlanetaryAndAnnulus
GearAssembly
1 - DRIVING SHELL 2 - ASSEMBLED FRONT PLANETARY AND ANNULUS GEARS
Fig.215AssemblingFrontPlanetaryAndAnnulus
Gears
1 - FRONT ANNULUS GEAR 2 - FRONT PLANETARY GEAR
Fig.217InstallingPlanetarySnap
1 - SNAP-RING PLIERS 2 - PLANETARY SNAP-RING
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PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(17) Check planetary geartrain end play with feeler gauge (Fig. 218). Insert gauge between rear annulus gear and shoulder on intermediate shaft as shown. End play should be 0.15 to 1.22 mm (0.006 to 0.048 in.).
(18) If end play is incorrect, install thinner/thicker
planetary snap-ring as needed.
REAR CLUTCH DESCRIPTION
The rear clutch assembly (Fig. 219) is composed of the rear clutch retainer, pressure plate, clutch plates, driving discs, piston, Belleville spring, and snap- rings. The Belleville spring acts as a lever to multi- ply the force applied on to it by the apply piston. The increased apply force on the rear clutch pack, in com- parison to the front clutch pack, is needed to hold against the greater torque load imposed onto the rear pack. The rear clutch is directly behind the front clutch and is considered a driving component.
Fig.218CheckingPlanetaryGeartrainEndPlay
1 - OUTPUT SHAFT 2 - REAR ANNULUS GEAR 3 - FEELER GAUGE
NOTE: The number of discs and plates may vary with each engine and vehicle combination.
1 - REAR CLUTCH RETAINER 2 - TORLON™ SEAL RINGS 3 - INPUT SHAFT 4 - PISTON RETAINER 5 - OUTPUT SHAFT THRUST WASHER 6 - INNER PISTON SEAL 7 - PISTON SPRING 8 - PRESSURE PLATE 9 - CLUTCH DISCS 10 - SNAP-RING (SELECTIVE)
Fig.219RearClutchComponents
11 - REACTION PLATE 12 - CLUTCH PLATES 13 - WAVE SPRING 14 - SPACER RING 15 - PISTON 16 - OUTER PISTON SEAL 17 - REAR SEAL RING 18 - FIBER THRUST WASHER 19 - RETAINING RING
DR REAR CLUTCH (Continued) OPERATION
To apply the clutch, pressure is applied between the clutch retainer and piston. The fluid pressure is provided 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 piston moves away from the clutch retainer and compresses 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 spring is used to cushion the application of the clutch pack. The snap-ring is selective and used to adjust clutch pack clearance.
When pressure is released from the piston, the spring returns the piston to its fully released position and disengages the clutch. The release spring also helps to cushion the application of the clutch assem- bly. 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 pis- ton. The check-valve is needed to eliminate the pos-
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force sibility of plate drag caused by centrifugal acting on the residual fluid trapped in the clutch pis- ton retainer.
DISASSEMBLY
(1) Remove fiber thrust washer from forward side
of clutch retainer.
(2) Remove input shaft front and rear seal rings. (3) Remove selective clutch pack snap-ring (Fig.
220).
(4) Remove the reaction plate, clutch discs, steel plates, pressure plate, wave spring, spacer ring, and piston spring (Fig. 220).
(5) Remove clutch piston with rotating motion. (6) Remove and discard piston seals. (7) Remove input shaft retaining ring. It may be necessary to press the input shaft in slightly to relieve tension on the retaining ring
(8) Press input shaft out of retainer with shop press and suitable size press tool. Use a suitably sized press tool to support the retainer as close to the input shaft as possible.
1 - REAR CLUTCH RETAINER 2 - TORLON™ SEAL RINGS 3 - INPUT SHAFT 4 - PISTON RETAINER 5 - OUTPUT SHAFT THRUST WASHER 6 - INNER PISTON SEAL 7 - PISTON SPRING 8 - PRESSURE PLATE 9 - CLUTCH DISCS 10 - SNAP-RING (SELECTIVE)
Fig.220RearClutchComponents
11 - REACTION PLATE 12 - CLUTCH PLATES 13 - WAVE SPRING 14 - SPACER RING 15 - PISTON 16 - OUTER PISTON SEAL 17 - REAR SEAL RING 18 - FIBER THRUST WASHER 19 - RETAINING RING
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REAR CLUTCH (Continued) CLEANINGClean the clutch components with solvent and dry them with compressed air. Do not use rags or shop towels to dry any of the clutch parts. Lint from such materials will adhere to component surfaces and could restrict or block fluid passages after assembly.
INSPECTION
Replace the clutch discs if warped, worn, scored, burned/charred, the lugs are damaged, or if the fac- ing is flaking off. Replace the top and bottom pres- sure plates if scored, warped, or cracked. Be sure the driving lugs on the pressure and clutch plates are also in good condition. The lugs must not be bent, cracked or damaged in any way.
Replace the piston spring and wave spring if either
part is distorted, warped or broken.
Check the lug grooves in the clutch retainer. The clutch and pressure plates should slide freely in the slots. Replace the retainer if the grooves are worn or damaged. Also check action of the check balls in the retainer and piston. Each check ball must move freely and not stick.
Replace the retainer bushing if worn, scored, or
doubt exists about bushing condition.
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 condition of the fiber thrust washer and metal output shaft thrust washer. Replace either washer if worn or damaged.
Check condition of the seal rings on the input shaft and clutch retainer hub. Replace the seal rings only if worn, distorted, or damaged. The input shaft front seal ring is teflon with chamfered ends. The rear ring is metal with interlocking ends.
Check the input shaft for wear, or damage. Replace
the shaft if worn, scored or damaged in any way.
ASSEMBLY
(1) Soak clutch discs in transmission fluid while
assembling other clutch parts.
(2) Install new seal rings on clutch retainer hub
and input shaft if necessary.
(a) Be sure clutch hub seal ring is fully seated in
groove and is not twisted. (3) Lubricate splined end of input shaft and clutch retainer with transmission fluid. Then partially press input shaft into retainer (Fig. 221). Use a suitably sized press tool to support retainer as close to input shaft as possible.
(4) Install input shaft retaining ring. (5) Press the input shaft the remainder of the way
into the clutch retainer.
DR
(6) Install new seals on clutch piston. Be sure lip
of each seal faces interior of clutch retainer.
(7) Lubricate lip of piston seals with generous quantity of Mopart Door Ease. Then lubricate retainer hub and bore with light coat of transmission fluid.
(8) Install clutch piston in retainer. Use twisting motion to seat piston in bottom of retainer. A thin strip of plastic (about 0.0209 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 tool to help ease the piston seals into place. Metal tools will cut, shave, or score the seals.
(9) Install piston spring in retainer and on top of piston. Concave side of spring faces downward (toward piston).
(10) Install the spacer ring and wave spring into the retainer. Be sure spring is completely seated in retainer groove.
Fig.221PressingInputShaftIntoRearClutch
Retainer
1 - INPUT SHAFT 2 - REAR CLUTCH RETAINER 3 - PRESS RAM
(11) Install pressure plate (Fig. 220). Ridged side of plate faces downward (toward piston) and flat side toward clutch pack.
(12) Install first clutch disc in retainer on top of pressure plate. Then install a clutch plate followed
DR REAR CLUTCH (Continued)
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by a clutch disc until entire clutch pack is installed (4 discs and 3 plates are required) (Fig. 220).
(13) Install the reaction plate. (14) Install selective snap-ring. Be sure snap-ring
is fully seated in retainer groove.
(15) Using a suitable gauge bar and dial indicator,
measure clutch pack clearance (Fig. 222).
(a) Position gauge bar across the clutch drum indicator pointer on the pressure
with the dial plate (Fig. 222).
(b) Using two small screw drivers, lift the pres-
sure plate and release it.
(c) Zero the dial indicator. (d) Lift the pressure plate until it contacts the
snap-ring and record the dial indicator reading. Clearance should be 0.635 - 0.914 mm (0.025 - 0.036 in.). If clearance is incorrect, steel plates, discs, selective snap ring and pressure plates may have to be changed.
The selective snap ring thicknesses are: † 0.107 - 0.109 in. † 0.098 - 0.100 in. † 0.095 - 0.097 in. † 0.083 - 0.085 in. † 0.076 - 0.078 in. † 0.071 - 0.073 in. † 0.060 - 0.062 in. (16) Coat rear clutch thrust washer with petro- leum jelly and install washer over input shaft and into clutch retainer (Fig. 223). Use enough petroleum jelly to hold washer in place.
(17) Set rear clutch aside for installation during
final assembly.
Fig.222CheckingRearClutchPackClearance
1 - DIAL INDICATOR 2 - PRESSURE PLATE 3 - SNAP-RING 4 - STAND 5 - REAR CLUTCH 6 - GAUGE BAR
Fig.223InstallingRearClutchThrustWasher
1 - REAR CLUTCH RETAINER 2 - REAR CLUTCH THRUST WASHER
REAR SERVO DESCRIPTION
The rear (low/reverse) servo consists of a single stage or diameter piston and a spring loaded plug. The spring is used to cushion the application of the rear (low/reverse) band.
OPERATION
While in the de-energized state (no pressure applied), the piston is held up in its bore by the pis- ton spring. The plug is held down in its bore, in the piston, by the plug spring. When pressure is applied to the top of the piston, the plug is forced down in its bore, taking up any clearance. As the piston moves, it causes the plug spring to compress, and the piston moves down over the plug. The piston continues to move down until it hits the shoulder of the plug and fully applies the band. The period of time from the initial application, until the piston is against the shoulder of the plug, represents a reduced shocking of the band that cushions the shift.
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REAR SERVO (Continued) DISASSEMBLY(1) Remove small snap-ring and remove plug and
spring from servo piston (Fig. 224).
(2) Remove and discard servo piston seal ring.
DR
(3) Assemble piston, plug, spring and new snap-
ring.
(4) Lubricate piston seal lip with petroleum jelly.
Fig.224RearServoComponents
1 - SNAP-RING 2 - PISTON SEAL 3 - PISTON PLUG 4 - SPRING RETAINER 5 - SNAP-RING 6 - PISTON SPRING 7 - CUSHION SPRING 8 - PISTON
CLEANING
Remove and discard the servo piston seal ring (Fig. 225). Then clean the servo components with solvent and dry with compressed air. Replace either spring if collapsed, distorted or broken. Replace the plug and piston if cracked, bent, or worn. Discard the servo snap-rings and use new ones at assembly.
Fig.226RearServoComponents
1 - SNAP-RING 2 - PISTON SEAL 3 - PISTON PLUG 4 - SPRING RETAINER 5 - SNAP-RING 6 - PISTON SPRING 7 - CUSHION SPRING 8 - PISTON
SHIFT MECHANISM DESCRIPTION
The gear shift mechanism provides six shift posi- tions which are: † PARK (P) † REVERSE (R) † NEUTRAL (N) † DRIVE (D) † Manual SECOND (2) † Manual LOW (1)
OPERATION
Fig.225RearServoComponents
1 - SNAP-RING 2 - PISTON SEAL 3 - PISTON PLUG 4 - SPRING RETAINER 5 - SNAP-RING 6 - PISTON SPRING 7 - CUSHION SPRING 8 - PISTON
ASSEMBLY
(1) Lubricate piston and guide seals (Fig. 226) with petroleum jelly. Lubricate other servo parts with Mopart ATF +4, Automatic Transmission fluid.
(2) Install new seal ring on servo piston.
Manual LOW (1) range provides first gear only. Overrun braking is also provided in this range. Man- ual SECOND (2) range provides first and second gear only.
DRIVE range provides first, second third and over- drive fourth gear ranges. The shift into overdrive fourth gear range occurs only after the transmission has completed the shift into D third gear range. No further movement of the shift mechanism is required to complete the 3-4 shift.
The fourth gear upshift occurs automatically when the overdrive selector switch is in the ON position. No upshift to fourth gear will occur if any of the fol- lowing are true: † The transmission fluid temperature is below 10° † The shift to third is not yet complete. † Vehicle speed is too low for the 3-4 shift to occur. † Battery temperature is below -5° C (23° F).
C (50° F) or above 121° C (250° F).
DR
SOLENOID DESCRIPTION
The typical electrical solenoid used in automotive applications is a linear actuator. It is a device that produces motion in a straight line. This straight line motion can be either forward or backward in direc- tion, and short or long distance.
A solenoid is an electromechanical device that uses a magnetic force to perform work. It consists of a coil of wire, wrapped around a magnetic core made from steel or iron, and a spring loaded, movable plunger, which performs the work, or straight line motion.
The solenoids used in transmission applications are attached to valves which can be classified as nor- mally open or normally closed. The normally open solenoid valve is defined as a valve which allows hydraulic flow when no current or voltage is applied to the solenoid. The normally closed sole- noid valve is defined as a valve which does not allow hydraulic flow when no current or voltage is applied to the solenoid. These valves perform hydraulic con- trol functions for the transmission and must there- fore be durable and tolerant of dirt particles. For these reasons, the valves have hardened steel pop- pets and ball valves. The solenoids operate the valves directly, which means that the solenoids must have very high outputs to close the valves against the siz- able flow areas and line pressures found in current transmissions. Fast response time is also necessary to ensure accurate control of the transmission.
The strength of the magnetic field is the primary force that determines the speed of operation in a par- ticular solenoid design. A stronger magnetic field will cause the plunger to move at a greater speed than a weaker one. There are basically two ways to increase the force of the magnetic field:
1. Increase the amount of current applied to the
coil or
2. Increase the number of turns of wire in the coil. The most common practice is to increase the num- ber of turns by using thin wire that can completely fill the available space within the solenoid housing. The strength of the spring and the length of the plunger also contribute to the response speed possi- ble by a particular solenoid design.
is controlled. Some of
A solenoid can also be described by the method by which it the possibilities include variable force, pulse-width modulated, con- stant ON, or duty cycle. The variable force and pulse- width modulated versions utilize similar methods to control the current flow through the solenoid to posi- tion the solenoid plunger at a desired position some- where between full ON and full OFF. The constant ON and duty cycled versions control the voltage
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across the solenoid to allow either full flow or no flow through the solenoid’s valve.
OPERATION
When an electrical current is applied to the sole- noid coil, a magnetic field is created which produces an attraction to the plunger, causing the plunger to move and work against the spring pressure and the load applied by the fluid the valve is controlling. The plunger is normally directly attached to the valve which it is to operate. When the current is removed from the coil, the attraction is removed and the plunger will return to its original position due to spring pressure.
The plunger is made of a conductive material and accomplishes this movement by providing a path for the magnetic field to flow. By keeping the air gap between the plunger and the coil to the minimum necessary to allow free movement of the plunger, the magnetic field is maximized.
SPEED SENSOR DESCRIPTION
The speed sensor (Fig. 227) is located in the over- drive gear case. The sensor is positioned over the park gear and monitors transmission output shaft rotating speed.
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
DR
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
21 - 433
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
21 - 434
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
AUTOMATIC TRANSMISSION - 48RE
21 - 435
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
AUTOMATIC TRANSMISSION - 48RE
21 - 436
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
21 - 437
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
21 - 438
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
21 - 439
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.
21 - 440
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
DR
AUTOMATIC TRANSMISSION - 48RE
21 - 441
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
21 - 442
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
21 - 443
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
21 - 444
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).
DR
AUTOMATIC TRANSMISSION - 48RE
21 - 445
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).
21 - 446
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)
AUTOMATIC TRANSMISSION - 48RE
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
21 - 448
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
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Fig.255RegulatorValveinParkPosition
Fig.256RegulatorValveinNeutralPosition
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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)
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Fig.258RegulatorValveinReversePosition
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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
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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
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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):
