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bearing. Bearing may remain on piston or in clutch hub during removal.
(13) Position drain pan on workbench. (14) Place overdrive unit over drain pan. Tilt unit
to drain residual fluid from case.
(15) Examine fluid for clutch material or metal fragments. If fluid contains these items, overhaul will be necessary.
(16) If overdrive unit does not require any service, leave alignment tool in position. Tool will prevent accidental misalignment of planetary gear and over- running clutch splines.
DR OVERDRIVE UNIT (Continued) DISASSEMBLY
(1) Remove transmission speed sensor and o-ring
seal from overdrive case (Fig. 125).
(2) Remove overdrive piston thrust bearing (Fig.
126).
AUTOMATIC TRANSMISSION - 48RE
21 - 399
OVERDRIVE PISTON
(1) Remove overdrive piston thrust plate (Fig. 127). Retain thrust plate. It is a select fit part and may possibly be reused.
Fig.127OverdrivePistonThrustPlateRemoval/
Installation
1 - OVERDRIVE PISTON 2 - OVERDRIVE PISTON SPACER (SELECT FIT)
(2) Remove intermediate shaft spacer (Fig. 128). Retain spacer. It is a select fit part and may possibly be reused.
Fig.125TransmissionSpeedSensor
1 - SOCKET AND WRENCH 2 - SPEED SENSOR 3 - O-RING
Fig.128IntermediateShaftSpacerLocation
1 - INTERMEDIATE SHAFT 2 - INTERMEDIATE SHAFT SPACER (SELECT FIT)
Fig.126OverdrivePistonThrustBearingRemoval/
Installation
1 - THRUST BEARING 2 - OVERDRIVE PISTON 3 - THRUST PLATE
21 - 400
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
(3) Remove overdrive piston from retainer (Fig.
129).
DR
Fig.129OverdrivePistonRemoval
1 - PISTON RETAINER 2 - OVERDRIVE PISTON
OVERDRIVE CLUTCH PACK
(1) Remove overdrive clutch pack wire retaining
ring (Fig. 130).
(2) Remove overdrive clutch pack (Fig. 131). (3) Note position of clutch pack components for
assembly reference (Fig. 132).
Fig.131OverdriveClutchPackRemoval
1 - OVERDRIVE CLUTCH PACK
Fig.132OverdriveClutchComponentPosition-
Typical
1 - REACTION PLATE 2 - CLUTCH PLATES
3 - PRESSURE PLATE 4 - CLUTCH DISCS
OVERDRIVE GEARTRAIN
(1) Remove overdrive clutch wave spring (Fig.
133), 5 disc clutch only.
Fig.130RemovingOverdriveClutchPackRetaining
Ring
1 - OVERDRIVE CLUTCH PACK RETAINING RING
Fig.133OverdriveClutchWaveSpringRemoval-5
DiscClutchOnly
1 - WAVE SPRING
DR OVERDRIVE UNIT (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 401
(2) Remove overdrive clutch reaction snap-ring (Fig. 134). Note that snap-ring is located in same groove as wave spring.
(5) Expand output shaft bearing snap-ring with expanding-type snap-ring pliers. Then push output shaft forward to release shaft bearing from locating ring (Fig. 137).
Fig.134OverdriveClutchReactionSnap-Ring
Removal
1 - REACTION RING 2 - CLUTCH HUB
(3) Remove Torx™ head screws that attach access
cover and gasket to overdrive case (Fig. 135).
(4) Remove access cover and gasket (Fig. 136).
Fig.137ReleasingBearingFromLocatingRing
1 - EXPAND BEARING LOCATING RING WITH SNAP-RING PLIERS 2 - ACCESS HOLE
(6) Lift gear case up and off geartrain assembly
(Fig. 138).
Fig.135AccessCoverScrewRemoval
1 - TORX SCREWDRIVER (T25) 2 - ACCESS COVER SCREWS
Fig.138RemovingGeartrain
1 - GEARTRAIN ASSEMBLY 2 - GEAR CASE
Fig.136AccessCoverAndGasketRemoval
1 - ACCESS COVER AND GASKET
21 - 402
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(7) Remove snap-ring that retains rear bearing on
(8) Remove rear bearing from output shaft (Fig.
output shaft.
139).
Fig.139RearBearingRemoval
1 - OUTPUT SHAFT 2 - REAR BEARING 3 - SNAP-RING
DIRECT CLUTCH, HUB AND SPRING
WARNING: THE NEXT STEP IN DISASSEMBLY INVOLVES COMPRESSING THE DIRECT CLUTCH SPRING. IT IS EXTREMELY IMPORTANT THAT PROPER EQUIPMENT BE USED TO COMPRESS THE SPRING AS SPRING FORCE IS APPROXI- MATELY 830 POUNDS. USE SPRING COMPRESSOR TOOL 6227-1 AND A HYDRAULIC SHOP PRESS WITH A MINIMUM RAM TRAVEL OF 5-6 INCHES. THE PRESS MUST ALSO HAVE A BED THAT CAN BE ADJUSTED UP OR DOWN AS REQUIRED. RELEASE CLUTCH SPRING TENSION SLOWLY AND COMPLETELY TO AVOID PERSONAL INJURY.
Fig.140GeartrainMountedInShopPress
1 - PRESS RAM 2 - SPECIAL TOOL C-3995-A (OR SIMILAR TOOL) 3 - CLUTCH HUB 4 - PLATES 5 - PRESS BED 6 - SPECIAL TOOL 6227-1
(1) Mount geartrain assembly in shop press (Fig.
140).
(2) Position Compressor Tool 6227-1 on clutch hub (Fig. 140). Support output shaft flange with steel press plates as shown and center assembly under press ram.
(3) Apply press pressure slowly. Compress hub and spring far enough to expose clutch hub retaining ring and relieve spring pressure on clutch pack snap-ring (Fig. 140).
DR OVERDRIVE UNIT (Continued)
(4) Remove direct clutch pack snap-ring (Fig. 141). (5) Remove direct clutch hub retaining ring (Fig.
142).
AUTOMATIC TRANSMISSION - 48RE
21 - 403
(6) Release press load slowly and completely (Fig.
143).
(7) Remove Special Tool 6227-1. Then remove clutch pack from hub (Fig. 143). Note the orientation of the clutch discs. The clutch pack consists of 23 sin- gle-sided discs and they must be installed in the same orientation as they were removed.
Fig.141DirectClutchPackSnap-RingRemoval
1 - CLUTCH HUB 2 - SPECIAL TOOL 6227-1
3 - DIRECT CLUTCH PACK SNAP-RING 4 - PRESS PLATES 5 - CLUTCH DRUMFig.143DirectClutchPackRemoval
1 - SPECIAL TOOL 6227-1
2 - DIRECT CLUTCH HUB 3 - DIRECT CLUTCH PACKGEARTRAIN
(1) Remove direct clutch hub and spring (Fig. 144).
Fig.142DirectClutchHubRetainingRingRemoval 1 - SPECIAL TOOL 6227-1
2 - CLUTCH HUB RETAINING RING 3 - PRESS BED 4 - PRESS PLATESFig.144DirectClutchHubAndSpringRemoval
1 - DIRECT CLUTCH SPRING 2 - DIRECT CLUTCH HUB
21 - 404
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
(2) Remove sun gear and spring plate. Then remove planetary thrust bearing and planetary gear (Fig. 145).
DR
(6) Mark position of annulus gear and direct clutch drum for assembly alignment reference (Fig. 147). Use small center punch or scriber to make alignment marks.
Fig.145RemovingSunGear,ThrustBearingAnd
PlanetaryGear
1 - PLANETARY GEAR 2 - PLANETARY THRUST BEARING 3 - CLUTCH SPRING PLATE 4 - SPRING PLATE SNAP-RING 5 - SUN GEAR
(3) Remove overrunning clutch assembly with expanding type snap-ring pliers (Fig. 146). Insert pli- ers into clutch hub. Expand pliers to grip hub splines and remove clutch with counterclockwise, twisting motion.
(4) Remove
thrust
bearing
from overrunning
clutch hub.
(5) Remove overrunning clutch from hub.
Fig.147MarkingDirectClutchDrumAndAnnulus
GearForAssemblyAlignment
1 - DIRECT CLUTCH DRUM 2 - HAMMER 3 - PUNCH
(7) Remove direct clutch drum rear retaining ring
(Fig. 148).
Fig.148ClutchDrumInnerRetainingRingRemoval 1 - INNER RETAINING RING 2 - DIRECT CLUTCH DRUM 3 - ANNULUS GEAR
Fig.146OverrunningClutchAssemblyRemoval/
Installation
1 - OVERRUNNING CLUTCH 2 - NEEDLE BEARING
DR OVERDRIVE UNIT (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 405
(8) Remove direct clutch drum outer retaining ring
(Fig. 149).
(9) Mark annulus gear and output shaft for assem- bly alignment reference (Fig. 150). Use punch or scriber to mark gear and shaft.
Fig.151AnnulusGearSnap-RingRemoval
1 - OUTPUT SHAFT 2 - ANNULUS GEAR 3 - SNAP-RING
Fig.149ClutchDrumOuterRetainingRingRemoval 1 - OUTER RETAINING RING
Fig.152AnnulusGearRemoval
1 - OUTPUT SHAFT 2 - ANNULUS GEAR
Fig.150MarkingAnnulusGearAndOutputShaft
ForAssemblyAlignment
1 - OUTPUT SHAFT 2 - HAMMER 3 - PUNCH
(10) Remove snap-ring that secures annulus gear on output shaft (Fig. 151). Use two screwdrivers to unseat and work snap-ring out of groove as shown.
(11) Remove annulus gear from output shaft (Fig. 152). Use rawhide or plastic mallet to tap gear off shaft.
GEAR CASE AND PARK LOCK
(1) Remove locating ring from gear case.
(2) Remove park pawl shaft retaining bolt and
remove shaft, pawl and spring.
(3) Remove reaction plug snap-ring and remove
reaction plug.
(4) Remove output shaft seal.
CLEANING
Clean the geartrain and case components with sol- vent. Dry all parts except the bearings with com- pressed air. Allow bearings to air dry.
Do not use shop towels for wiping parts dry unless the towels are made from a lint-free material. A suffi- cient quantity of lint (from shop towels, cloths, rags, etc.) could plug the transmission filter and fluid pas- sages.
Discard the old case gasket and seals. Do not attempt to salvage these parts. They are not reus-
21 - 406
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
able. Replace any of the overdrive unit snap-rings if distorted or damaged.
Minor nicks or scratches on components can be smoothed with crocus cloth. However, do not attempt to reduce severe scoring on any components with abrasive materials. Replace severely scored compo- nents; do not try to salvage them.
INSPECTION
Check condition of the park lock components and
the overdrive case.
Check the bushings in the overdrive case. Replace the bushings if severely scored or worn. Also replace the case seal if loose, distorted, or damaged.
Examine the overdrive and direct clutch discs and plates. Replace the discs if the facing is worn, severely scored, or burned and flaking off. Replace the clutch plates if worn, heavily scored, or cracked. Check the lugs on the clutch plates for wear. The plates should slide freely in the drum. Replace the plates or drum if binding occurs.
Check condition of the annulus gear, direct clutch hub, clutch drum and clutch spring. Replace the gear, hub and drum if worn or damaged. Replace the spring if collapsed, distorted, or cracked.
Be sure the splines and lugs on the gear, drum and hub are in good condition. The clutch plates and discs should slide freely in these components.
Inspect
the thrust bearings and spring plate. Replace the plate if worn or scored. Replace the bear- ings if rough, noisy, brinnelled, or worn.
Inspect the planetary gear assembly and the sun gear and bushings. If either the sun gear or the bushings are damaged, replace the gear and bush- ings as an assembly. The gear and bushings are not serviced separately.
The planetary carrier and pinions must be in good condition. Also be sure the pinion pins are secure and in good condition. Replace the carrier if worn or damaged. Inspect the overrunning clutch and race. The race surface should be smooth and free of scores. Replace the overrunning clutch assembly or the race if either assembly is worn or damaged in any way.
Replace the shaft pilot bushing and inner bushing if damaged. Replace either shaft bearing if rough or noisy. Replace the bearing snap-rings if distorted or cracked.
Check the machined surfaces on the output shaft. These surfaces should clean and smooth. Very minor nicks or scratches can be smoothed with crocus cloth. Replace the shaft if worn, scored or damaged in any way. Inspect the output shaft bushings. The small bush- ing is the intermediate shaft pilot bushing. The large bushing is the overrunning clutch hub bushing. Replace either bushing if scored, pitted, cracked, or worn.
DR
ASSEMBLY
GEARTRAIN AND DIRECT CLUTCH
(1) Soak direct clutch and overdrive clutch discs in Mopart ATF +4, Automatic Transmission fluid. Allow discs to soak for 10-20 minutes.
(2) Install annulus gear
if removed. Then install annulus gear retaining snap- ring (Fig. 153).
on output
shaft,
(3) Align and install clutch drum on annulus gear (Fig. 154). Be sure drum is engaged in annulus gear lugs.
(4) Install clutch drum outer retaining ring (Fig.
154).
Fig.153AnnulusGearInstallation
1 - SNAP-RING 2 - OUTPUT SHAFT FRONT BEARING 3 - ANNULUS GEAR
Fig.154ClutchDrumAndOuterRetainingRing
Installation
1 - ANNULUS GEAR 2 - OUTER SNAP-RING 3 - CLUTCH DRUM
DR OVERDRIVE UNIT (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 407
(5) Slide clutch drum forward and install
inner
retaining ring (Fig. 155).
(6) Install rear bearing and snap-ring on output shaft (Fig. 156). Be sure locating ring groove in bear- ing is toward rear.
Fig.155ClutchDrumInnerRetainingRing
Installation
1 - ANNULUS GEAR 2 - INNER SNAP-RING 3 - CLUTCH DRUM
Fig.156RearBearingAndSnap-RingInstallation 1 - REAR BEARING 2 - SNAP-RING
(7) Install overrunning clutch on hub (Fig. 157). Note that clutch only fits one way. Shoulder on clutch should seat in small recess at edge of hub.
(8) Install thrust bearing on overrunning clutch hub. Use generous amount of petroleum jelly to hold bearing in place for installation. Bearing fits one way only. Be sure bearing is seated squarely against hub. Reinstall bearing if it does not seat squarely.
(9) Install overrunning clutch in output shaft (Fig. 158). Insert snap-ring pliers in hub splines. Expand pliers to grip hub. Then install assembly with coun- terclockwise, twisting motion.
Fig.157AssemblingOverrunningClutchAndHub 1 - CLUTCH HUB 2 - OVERRUNNING CLUTCH
Fig.158OverrunningClutchInstallation
1 - CLUTCH DRUM 2 - OVERRUNNING CLUTCH ASSEMBLY 3 - EXPANDING-TYPE SNAP-RING PLIERS 4 - CLUTCH DRUM 5 - ANNULUS GEAR 6 - OVERRUNNING CLUTCH ASSEMBLY SEATED IN OUTPUT SHAFT
21 - 408
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
(10) Install planetary gear in annulus gear (Fig. 159). Be sure planetary pinions are fully seated in annulus gear before proceeding.
DR
Fig.161SunGearInstallation
1 - SUN GEAR AND SPRING PLATE ASSEMBLY
(14) Mount assembled output shaft, annulus gear, and clutch drum in shop press. Direct clutch spring, hub and clutch pack are easier to install with assem- bly mounted in press.
(15) Align splines in hubs of planetary gear and overrunning clutch with Alignment tool 6227-2 (Fig. 162). Insert tool through sun gear and into splines of both hubs. Be sure alignment tool is fully seated before proceeding.
Fig.159PlanetaryGearInstallation
1 - PLANETARY GEAR 2 - ANNULUS GEAR
(11) Coat planetary thrust bearing and bearing contact surface of spring plate with generous amount of petroleum jelly. This will help hold bearing in place during installation.
(12) Install planetary thrust bearing on sun gear (Fig. 160). Slide bearing onto gear and seat it against spring plate as shown. Bearing fits one way only. If it does not seat squarely against spring plate, remove and reposition bearing.
(13) Install assembled sun gear, spring plate and thrust bearing (Fig. 161). Be sure sun gear and thrust bearing are fully seated before proceeding.
Fig.160PlanetaryThrustBearingInstallation
1 - SPRING PLATE 2 - PLANETARY THRUST BEARING 3 - SUN GEAR
Fig.162AlignmentToolInstallation
1 - SPECIAL TOOL 6227-2
2 - PRESS PLATES 3 - ASSEMBLED DRUM AND ANNULUS GEAR 4 - SUN GEARDR OVERDRIVE UNIT (Continued)
(16) Install direct clutch spring (Fig. 163). Be sure
spring is properly seated on spring plate.
AUTOMATIC TRANSMISSION - 48RE
21 - 409
Fig.163DirectClutchSpringInstallation
1 - SPECIAL TOOL 6227-2
2 - DIRECT CLUTCH SPRING 3 - CLUTCH HUB 4 - PRESS PLATESNOTE: The direct clutch in a 48RE transmission uses 23 single-sided clutch discs.
Fig.164CorrectPositionOfDirect
ClutchReactionPlate
1 - REACTION PLATE COUNTERBORE 2 - DIRECT CLUTCH REACTION PLATE (FLUSH WITH END OF HUB) 3 - CLUTCH HUB
(17) Assemble and install direct clutch pack on
hub as follows:
(a) Install direct clutch reaction plate on clutch hub first. Note that one side of reaction plate is counterbored. Be sure this side faces rearward. Splines at rear of hub are raised slightly. Counter- bore in plate fits over raised splines. Plate should be flush with this end of hub (Fig. 164).
(b) Install first clutch disc with external lugs fol- lowed by a disc with internal spline teeth. Con- tinue alternating internal and external discs until all discs have been installed.
(c) Install pressure plate. This is last clutch pack item to be installed. Be sure plate is installed with shoulder side facing upward (Fig. 165).
Fig.165CorrectPositionOfDirectClutch
1 - DIRECT CLUTCH PRESSURE PLATE 2 - CLUTCH PACK 3 - BE SURE SHOULDER SIDE OF PLATE FACES UPWARD
21 - 410
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
(18) Install clutch hub and clutch pack on direct clutch spring (Fig. 166). Be sure hub is started on sun gear splines before proceeding.
Fig.166DirectClutchPackAndClutchHub
Installation
1 - CLUTCH HUB 2 - DIRECT CLUTCH PACK 3 - CLUTCH DRUM
WARNING: THE NEXT STEP IN GEARTRAIN ASSEMBLY INVOLVES COMPRESSING THE DIRECT CLUTCH HUB AND SPRING. IT IS EXTREMELY IMPORTANT THAT PROPER EQUIPMENT BE USED TO COMPRESS THE SPRING AS SPRING FORCE IS APPROXIMATELY 830 POUNDS. USE COMPRES- SOR TOOL C-6227-1 AND A HYDRAULIC-TYPE SHOP PRESS WITH A MINIMUM RAM TRAVEL OF 6
INCHES. THE PRESS MUST ALSO HAVE A BED THAT CAN BE ADJUSTED UP OR DOWN AS REQUIRED. RELEASE CLUTCH SPRING TENSION SLOWLY AND COMPLETELY TO AVOID PERSONAL INJURY.(19) Position Compressor Tool 6227-1 on clutch
hub.
(20) Compress clutch hub and spring just enough
to place tension on hub and hold it in place.
(21) Slowly compress clutch hub and spring. Com- press spring and hub only enough to expose ring grooves for clutch pack snap-ring and clutch hub retaining ring.
(22) Realign clutch pack on hub and seat clutch
discs and plates in clutch drum.
DR
(23) Install direct clutch pack snap-ring (Fig. 167). Be very sure snap-ring is fully seated in clutch drum ring groove.
(24) Install clutch hub retaining ring (Fig. 168). Be very sure retaining ring is fully seated in sun gear ring groove.
(25) Slowly release press ram, remove compressor
tools and remove geartrain assembly.
Fig.167DirectClutchPackSnap-RingInstallation 1 - SPECIAL TOOL 6227-1
2 - DIRECT CLUTCH PACK SNAP-RINGFig.168ClutchHubRetainingRingInstallation
1 - SPECIAL TOOL 6227-1
2 - CLUTCH HUB RETAINING RINGDR OVERDRIVE UNIT (Continued) GEAR CASE
(1) Position park pawl and spring in case and install park pawl shaft. Verify that end of spring with 90° bend is hooked to pawl and straight end of spring is seated against case.
(2) Install pawl shaft retaining bolt. Tighten bolt
to 27 N·m (20 ft. lbs.) torque.
(3) Install park lock reaction plug. Note that plug has locating pin at rear (Fig. 169). Be sure pin is seated in hole in case before installing snap-ring.
(4) Install reaction plug snap-ring (Fig. 170). Com- press snap-ring only enough for installation; do not distort it.
AUTOMATIC TRANSMISSION - 48RE
21 - 411
(5) Verify that tab ends of rear bearing locating ring extend into access hole in gear case (Fig. 171). (6) Support geartrain on Tool 6227-1 (Fig. 172). Be
sure tool is securely seated in clutch hub.
(7) Install overdrive gear case on geartrain (Fig.
172).
Fig.169ReactionPlugLocatingPinAndSnap-Ring 1 - REACTION PLUG SNAP-RING (DO NOT OVERCOMPRESS TO INSTALL) 2 - LOCATING PIN 3 - PARK LOCK REACTION PLUG
Fig.171CorrectRearBearingLocatingRing
Position
1 - CASE ACCESS HOLE 2 - TAB ENDS OF LOCATING RING
Fig.170ReactionPlugAndSnap-RingInstallation 1 - REACTION PLUG SNAP-RING 2 - SNAP-RING PLIERS
1 - GEARTRAIN ASSEMBLY 2 - GEAR CASE
Fig.172OverdriveGearCaseInstallation
21 - 412
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(8) Expand front bearing locating ring with snap- ring pliers (Fig. 173). Then slide case downward until locating ring locks in bearing groove and release snap-ring.
(9) Install locating ring access cover and gasket in
overdrive unit case (Fig. 174).
Fig.173SeatingLocatingRingInRearBearing
1 - EXPAND BEARING LOCATING RING WITH SNAP-RING PLIERS 2 - ACCESS HOLE
Fig.174LocatingRingAccessCoverAndGasket
Installation
1 - TORX SCREWDRIVER (T25) 2 - ACCESS COVER SCREWS
OVERDRIVE CLUTCH
NOTE: The overdrive clutch in a 48RE transmission uses 5 or 6 clutch discs depending on the applica- tion.
(1) Install overdrive clutch reaction ring first.
Reaction ring is flat with notched ends (Fig. 175).
(2) For 5 disc overdrive clutch versions,
install wave spring on top of reaction ring (Fig. 176). Reac- tion ring and wave ring both fit in same ring groove. Use screwdriver to seat each ring securely in groove.
Also ensure that the ends of the two rings are offset from each other.
(3) Assemble overdrive clutch pack.
Fig.175OverdriveClutchReactionRingInstallation 1 - REACTION RING 2 - CLUTCH HUB
Fig.176OverdriveClutchWaveSpringInstallation-
5DiscClutchOnly
1 - WAVE SPRING
(4) Install overdrive clutch reaction plate first. (5) Install first clutch disc followed by first clutch plate. Then install remaining clutch discs and plates in same order.
(6) Install clutch pack pressure plate. (7) Install clutch pack wire-type retaining ring
(Fig. 177).
INTERMEDIATE SHAFT SPACER SELECTION
(1) Place overdrive unit in vertical position. Mount it on blocks, or in workbench with appropriate size mounting hole cut into it. Be sure unit is facing upward for access to direct clutch hub. Also be sure output shaft is not loaded and internal components are moved rearward for accurate measurement.
(2) Determine correct thickness intermediate shaft
spacer as follows:
(a) Insert Special Tool 6312 through sun gear, planetary gear and into pilot bushing in output shaft. Be sure tool bottoms against planetary shoulder.
DR OVERDRIVE UNIT (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 413
Fig.179IntermediateShaftEndPlaySpacer
Selection
Fig.177OverdriveClutchPackRetainingRing
Installation
1 - OVERDRIVE CLUTCH PACK RETAINING RING
(b) Position Gauge Tool 6311 across face of over- drive case (Fig. 178). Then position Dial Caliper C-4962 over gauge tool.
(c) Extend sliding scale of dial caliper downward through gauge tool slot until scale contacts end of Gauge Alignment Tool 6312. Lock scale in place. Remove dial caliper tool and note distance mea- sured (Fig. 178).
(d) Select proper thickness end play spacer from spacer chart based on distance measured (Fig. 179).
(e) Remove Gauge Alignment Tool 6312.
upward for access to direct clutch hub. Also be sure output shaft is not loaded and internal components are moved rearward for accurate measurement.
(2) Determine correct thickness overdrive piston
thrust plate as follows:
(a) Position Gauge Tool 6311 across face of over- drive case. Then position Dial Caliper C-4962 over gauge tool (Fig. 180).
(b) Measure distance to clutch hub thrust bear- ing seat at four points 90° apart. Then average measurements by adding them and dividing by 4. (c) Select and install required thrust plate from
information in thrust plate chart (Fig. 181). (3) Leave Alignment Tool 6227-2 in place. Tool will keep planetary and clutch hub splines in alignment until overdrive unit is ready for installation on trans- mission.
(4) Transmission speed sensor can be installed at this time if desired. However, it is recommended that sensor not be installed until after overdrive unit is secured to transmission.
Fig.178ShaftEndPlayMeasurement
1 - SPECIAL TOOL 6312
2 - SPECIAL TOOL 6311
3 - SPECIAL TOOL C-4962OD THRUST PLATE SELECTION
(1) Place overdrive unit in vertical position. Mount it on blocks, or in workbench with appropriate size mounting hole cut into it. Be sure unit is facing
Fig.180OverdrivePistonThrustPlateMeasurement 1 - SPECIAL TOOL 6311
2 - DIRECT CLUTCH HUB THRUST BEARING SEAT 3 - SPECIAL TOOL C-496221 - 414
OVERDRIVE UNIT (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(3) Cut out old case gasket around piston retainer
with razor knife (Fig. 182).
(4) Use old gasket as template and trim new gas-
ket to fit.
(5) Position new gasket over piston retainer and on transmission case. Use petroleum jelly to hold gasket in place if necessary. Do not use any type of sealer to secure gasket. Use petroleum jelly only.
Fig.181OverdrivePistonThrustPlateSelection
OVERDRIVE PISTON
(1) Install new seals on overdrive piston. (2) Stand transmission case upright on bellhous-
ing.
(3) Position Guide Ring 8114-1 on outer edge of
overdrive piston retainer.
overdrive piston retainer.
(4) Position Seal Guide 8114-3 on inner edge of
(5) Install overdrive piston in overdrive piston
retainer by:
(a) Aligning locating lugs on overdrive piston to
the two mating holes in retainer.
(b) Lubricate overdrive piston seals with Mopart
ATF+4.
retainer.
(c) Install piston over Seal Guide 8114-3 and
inside Guide Ring 8114-1.
(d) Push overdrive piston into position in
(e) Verify that the locating lugs entered the lug
bores in the retainer. (6) Install intermediate shaft spacer on intermedi-
ate shaft.
drive piston.
drive piston.
(7) Install overdrive piston thrust plate on over-
(8) Install overdrive piston thrust bearing on over-
(9) Install transmission speed sensor and o-ring
seal in overdrive case.
INSTALLATION
(1) Be sure overdrive unit Alignment Tool 6227-2
is fully seated before moving unit. If tool is not seated and gear splines rotate out of alignment, over- drive unit will have to be disassembled in order to realign splines.(2) If overdrive piston retainer was not removed during service and original case gasket is no longer reusable, prepare new gasket by trimming it.
Fig.182TrimmingOverdriveCaseGasket
1 - GASKET 2 - SHARP KNIFE
(6) Install selective spacer on intermediate shaft, if removed. Spacer goes in groove just rearward of shaft rear splines (Fig. 183).
Fig.183IntermediateShaftSelectiveSpacer
Location
1 - SELECTIVE SPACER 2 - SPACER GROOVE 3 - INTERMEDIATE SHAFT
(7) Install thrust bearing in overdrive unit sliding hub. Use petroleum jelly to hold bearing in position.
CAUTION: Be sure the shoulder on the inside diam- eter of the bearing is facing forward.
(8) Verify that splines in overdrive planetary gear and overrunning clutch hub are aligned with Align-
DR OVERDRIVE UNIT (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 415
ment Tool 6227-2. Overdrive unit cannot be installed if splines are not aligned. If splines have rotated out of alignment, unit will have to be disassembled to realign splines.
(9) Carefully slide Alignment Tool 6227-2 out of over-
drive planetary gear and overrunning clutch splines.
(10) Raise overdrive unit and carefully slide it straight onto intermediate shaft. Insert park rod into park lock reaction plug at same time. Avoid tilting overdrive during installation as this could cause planetary gear and overrunning clutch splines to rotate out of alignment. If this occurs, it will be nec- essary to remove and disassemble overdrive unit to realign splines.
(11) Work overdrive unit forward on intermediate
shaft until seated against transmission case.
(12) Install bolts attaching overdrive unit to trans- mission unit. Tighten bolts in diagonal pattern to 34
N·m (25 ft-lbs).(13) Connect the transmission speed sensor and
overdrive wiring connectors.
(14) Install the transfer case, if equipped. (15) Align and install rear propeller shaft, if nec- essary. (Refer to 3 - DIFFERENTIAL & DRIVELINE/ PROPELLER INSTALLATION)
SHAFT/PROPELLER
SHAFT
OVERRUNNING CLUTCH CAM/OVERDRIVE PISTON RETAINER DESCRIPTION
The overrunning clutch (Fig. 184) consists of an inner race, an outer race (or cam), rollers and springs, and the spring retainer. The number of roll- ers and springs depends on what transmission and which overrunning clutch is being dealt with.
OPERATION
As the inner race is rotated in a clockwise direction (as viewed from the front of the transmission), the race causes the rollers to roll toward the springs, causing them to compress against their retainer. The compression of the springs increases the clearance between the rollers and cam. This increased clear- ance between the rollers and cam results in a free- wheeling condition. When the inner race attempts to rotate counterclockwise, the action causes the rollers to roll in the same direction as the race, aided by the pushing of the springs. As the rollers try to move in the same direction as the inner race, they are wedged between the inner and outer races due to the design of the cam. In this condition, the clutch is locked and acts as one unit.
Fig.184OverrunningClutch
1 - OUTER RACE (CAM) 2 - ROLLER 3 - SPRING 4 - SPRING RETAINER 5 - INNER RACE (HUB)
DISASSEMBLY
(1) Remove the overdrive piston (Fig. 185). (2) Remove the overdrive piston retainer bolts. (3) Remove overdrive piston retainer. (4) Remove case gasket.
Fig.185OverdrivePistonRemoval
1 - OVERDRIVE CLUTCH PISTON 2 - INTERMEDIATE SHAFT 3 - SELECTIVE SPACER 4 - PISTON RETAINER
21 - 416
OVERRUNNING CLUTCH CAM/OVERDRIVE PISTON RETAINER (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(5) Tap old cam out of case with pin punch. Insert punch through bolt holes at rear of case (Fig. 186). Alternate position of punch to avoid cocking cam dur- ing removal.
(6) Clean clutch cam bore and case. Be sure to remove all chips/shavings generated during cam removal.
are aligned (Fig. 187). Then tap cam into case just enough to hold it in place.
(3) Verify that cam is correctly positioned before proceeding any further. Narrow ends of cam ramps should be to left when cam is viewed from front end of case (Fig. 187).
(4) Insert Adapter Tool SP-5124 into piston
retainer (Fig. 188).
Fig.186OverrunningClutchCam
1 - PIN PUNCH 2 - REAR SUPPORT BOLT HOLES
CLEANING
Clean the overrunning clutch assembly, clutch cam, low-reverse drum, and overdrive piston retainer in solvent. Dry them with compressed air after clean- ing.
INSPECTION
Fig.187PositioningReplacementClutchCamIn
Case
1 - ALIGN SERRATIONS ON CAM AND IN CASE 2 - CLUTCH CAM
Inspect condition of each clutch part after cleaning. Replace the overrunning clutch roller and spring assembly if any rollers or springs are worn or dam- aged, or if the roller cage is distorted, or damaged. Replace the cam if worn, cracked or damaged.
Replace the low-reverse drum if the clutch race, roller surface or inside diameter is scored, worn or damaged. Do not remove the clutch race from the low-reverse drum under any circumstances. Replace the drum and race as an assembly if either component is damaged.
Examine the overdrive piston retainer carefully for wear, cracks, scoring or other damage. Be sure the retainer hub is a snug fit in the case and drum. Replace the retainer if worn or damaged.
ASSEMBLY
Fig.188PositioningAdapterToolInOverdrive
PistonRetainer
1 - PISTON RETAINER 2 - SPECIAL TOOL SP-5124
(1) Temporarily install overdrive piston retainer in
case. Use 3-4 bolts to secure retainer.
(2) Align and start new clutch cam in the trans- mission case. Be sure serrations on cam and in case
DR OVERRUNNING CLUTCH CAM/OVERDRIVE PISTON RETAINER (Continued)
AUTOMATIC TRANSMISSION - 48RE
21 - 417
(5) Assemble Puller Bolt SP-3701 and Press Plate
SP-3583-A (Fig. 189).
Fig.190PositioningPullerPlateOnClutchCam
1 - SPECIAL TOOL SP-3701
2 - BE SURE PLATE SP-3583-A IS SEATED SQUARELY ON CAMFig.189AssemblingClutchCamPullerBoltAnd
PressPlate
1 - PULLER BOLT SP-3701
2 - PRESS PLATE SP-3583-A(6) Install assembled puller plate and bolt (Fig. 190). Insert bolt through cam, case and adapter tool. Be sure plate is seated squarely on cam.
(7) Hold puller plate and bolt in place and install
puller nut SP-3701 on puller bolt (Fig. 191).
(8) Tighten puller nut to press clutch cam into case (Fig. 191). Be sure cam is pressed into case evenly and does not become cocked.
(9) Remove clutch cam installer tools. (10) Stake case in 14 places around clutch cam to help secure cam in case. Use blunt punch or chisel to stake case.
(11) Remove piston retainer
from case. Cover retainer with plastic sheeting, or paper to keep it dust free.
(12) Clean case and cam thoroughly. Be sure any chips/shavings generated during cam installation are removed from case.
Fig.191PressingOverrunningClutchCamInto
Case
1 - SPECIAL TOOL SP-3583-A 2 - TIGHTEN NUT TO DRAW CAM INTO CASE (NUT IS PART OF BOLT SP-3701) 3 - SPECIAL TOOL SP-5124
4 - SPECIAL TOOL SP-370121 - 418
OVERRUNNING CLUTCH CAM/OVERDRIVE PISTON RETAINER (Continued)AUTOMATIC TRANSMISSION - 48RE
DR
(13) Install new gasket at rear of transmission case. Use petroleum jelly to hold gasket in place. Be sure to align governor feed holes in gasket with feed passages in case (Fig. 192). Also install gasket before overdrive piston retainer. Center hole in gasket is smaller than retainer and cannot be installed over retainer.
(14) Position overdrive piston retainer on trans- mission case and align bolt holes in retainer, gasket and case (Fig. 193). Then install and tighten retainer bolts to 17 N·m (13 ft. lbs.) torque.
Fig.193AligningOverdrivePistonRetainer
1 - PISTON RETAINER 2 - GASKET 3 - RETAINER BOLTS
(e) Verify that the locating lugs entered the lug
bores in the retainer.
PISTONS DESCRIPTION
There are several sizes and types of pistons used in an automatic transmission. Some pistons are used to apply clutches, while others are used to apply bands. They all have in common the fact that they are round or circular in shape, located within a smooth walled cylinder, which is closed at one end and con- verts fluid pressure into mechanical movement. The fluid pressure exerted on the piston is contained within the system through the use of piston rings or seals.
OPERATION
The principal which makes this operation possible is known as Pascal’s Law. Pascal’s Law can be stated as: “Pressure on a confined fluid is transmitted equally in all directions and acts with equal force on equal areas.”
Fig.192Installing/AligningCaseGasket
1 - CASE GASKET 2 - BE SURE GOVERNOR TUBE FEED HOLES IN CASE AND GASKET ARE ALIGNED
(15) Install new seals on overdrive piston. (16) Stand transmission case upright on bellhous-
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.
AUTOMATIC TRANSMISSION - 48RE
21 - 419
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.
AUTOMATIC TRANSMISSION - 48RE
21 - 420
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
AUTOMATIC TRANSMISSION - 48RE
21 - 421
(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
21 - 422
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
AUTOMATIC TRANSMISSION - 48RE
21 - 423
(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
21 - 424
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)
AUTOMATIC TRANSMISSION - 48RE
21 - 425
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
21 - 426
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-
AUTOMATIC TRANSMISSION - 48RE
21 - 427
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
AUTOMATIC TRANSMISSION - 48RE
21 - 428
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)
AUTOMATIC TRANSMISSION - 48RE
21 - 429
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.
AUTOMATIC TRANSMISSION - 48RE
21 - 430
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
AUTOMATIC TRANSMISSION - 48RE
21 - 431
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.
