OPERATION
As the torque converter rotates, the converter hub rotates the oil pump drive gear. As the drive gear rotates both
driven gears, a vacuum is created when the gear teeth come out of mesh. This suction draws fluid through the
pump inlet from the oil pan. As the gear teeth come back into mesh, pressurized fluid is forced into the pump outlet
and to the oil pump valves.
At low speeds, both sides of the pump supply fluid to the transmission. As the speed of the torque converter
increases, the flow from both sides increases until the flow from the primary side alone is sufficient to meet system
demands. At this point, the check valve located between the two pumps closes. The secondary side is shut down
and the primary side supplies all the fluid to the transmission.
CONVERTER CLUTCH SWITCH VALVE
The converter clutch switch valve is used to control the hydraulic pressure supplied to the front (OFF) side of the
torque converter clutch.
CONVERTER CLUTCH REGULATOR VALVE
The converter clutch regulator valve is used to control the hydraulic pressure supplied to the back (ON) side of the
torque converter clutch.
TORQUE CONVERTER LIMIT VALVE
The torque converter limit valve serves to limit the available line pressure to the torque converter clutch.
STANDARD PROCEDURE - OIL PUMP VOLUME CHECK
Measuring the oil pump output volume will determine if sufficient oil flowto the transmission oil cooler exists, and
whether or not an internal transmission failure is present.
Verify that the transmission fluid is at the proper level. Refer to the Fluid Level Check procedure in this section. If
necessary, fill the transmission to the proper level with Mopar
ATF +4, Automatic Transmission Fluid.
1. Disconnect theTo coolerline at the cooler inlet and place a collecting container under the disconnected line.
CAUTION: With the fluid set at the proper level, fluid collection should not exceed (1) quart or internal dam-
age to the transmission may occur.
2. Run the engineat 1800 rpm, with the shift selector in neutral. Verify that the transmission fluid temperature is
below 104.5° C (220° F) for this test.
3. If one quart of transmission fluid is collected in the container in 30 seconds or less, oil pump flow volume is
within acceptable limits. If fluid flow is intermittent, or it takes more than 30 seconds to collect one quart of fluid,
refer to the Hydraulic Pressure tests in this section for further diagnosis.
4. Re-connect theTo c o o l e rline to the transmission cooler inlet.
5. Refill the transmission to proper level.
page page
AUTOMATIC TRANSMISSION - 48RE - SERVICE
INFORMATION
DESCRIPTION ............................. 1268
OPERATION ............................... 1271
DIAGNOSIS AND TESTING
AUTOMATIC TRANSMISSION .............. 1277
PRELIMINARY ............................ 1277
ROAD TESTING .......................... 1277
HYDRAULIC PRESSURE TEST . ........... 1278
AIR TESTING TRANSMISSION CLUTCH
AND BAND OPERATION................... 1281
CONVERTER HOUSING FLUID LEAK ...... 1282
DIAGNOSIS CHARTS ..................... 1283
STANDARD PROCEDURE - ALUMINUM
THREAD REPAIR ......................... 1293
REMOVAL ................................. 1294
DISASSEMBLY ............................. 1298
CLEANING ................................. 1306
INSPECTION ............................... 1306
ASSEMBLY . ............................... 1307
INSTALLATION ............................. 1317
SCHEMATICS AND DIAGRAMS
HYDRAULIC SCHEMATICS ................ 1322
SPECIFICATIONS
TRANSMISSION .......................... 1336
SPECIAL TOOLS
RE TRANSMISSION ...................... 1339
ACCUMULATOR
DESCRIPTION ............................. 1341
OPERATION ............................... 1342
INSPECTION ............................... 1342
BANDS
DESCRIPTION ............................. 1343
OPERATION ............................... 1343
ADJUSTMENTS
ADJUSTMENT - BANDS ................... 1344
SYSTEM-BRAKE TRANSMISSION SHIFT
INTERLOCK
DESCRIPTION ............................. 1345
OPERATION ............................... 1345
DIAGNOSIS AND TESTING - BRAKE
TRANSMISSION SHIFT INTERLOCK ........ 1345
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK ....................... 1345
GOVERNOR-ELECTRONIC
DESCRIPTION ............................. 1347
OPERATION ............................... 1348
REMOVAL ................................. 1349
INSTALLATION ............................. 1350SEAL-EXTENSION HOUSING
REMOVAL ................................. 1352
INSTALLATION ............................. 1352
FLUID AND FILTER
DIAGNOSIS AND TESTING
EFFECTS OF INCORRECT FLUID LEVEL . . . 1353
CAUSES OF BURNT FLUID ............... 1353
FLUID CONTAMINATION .................. 1353
STANDARD PROCEDURE
FLUID LEVEL CHECK ..................... 1353
FLUID AND FILTER REPLACEMENT ....... 1355
TRANSMISSION FILL ..................... 1357
CLUTCH-FRONT
DESCRIPTION ............................. 1358
OPERATION ............................... 1358
DISASSEMBLY . ............................ 1359
INSPECTION............................... 1360
ASSEMBLY................................ 1360
SERVO-FRONT
DESCRIPTION ............................. 1363
OPERATION ............................... 1363
DISASSEMBLY . ............................ 1364
CLEANING ................................. 1364
INSPECTION ............................... 1365
ASSEMBLY................................ 1365
CABLE-GEARSHIFT
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE ................................... 1366
REMOVAL ................................. 1366
INSTALLATION ............................. 1367
ADJUSTMENTS - GEARSHIFT CABLE ........ 1368
PUMP-OIL
DESCRIPTION ............................. 1369
OPERATION ............................... 1369
DISASSEMBLY ............................. 1370
CLEANING ................................. 1371
INSPECTION ............................... 1371
ASSEMBLY................................ 1373
BEARING-OUTPUT SHAFT FRONT
REMOVAL ................................. 1375
INSTALLATION ............................. 1375
BEARING-OUTPUT SHAFT REAR
REMOVAL ................................. 1376
INSTALLATION ............................. 1376
CLUTCH-OVERDRIVE
DESCRIPTION ............................. 1377
OPERATION ............................... 1377
UNIT-OVERDRIVE
REMOVAL ................................. 1378
DISASSEMBLY ............................. 1379
OPERATION
The application of each driving or holding component is controlled by the valve body based upon the manual lever
position, throttle pressure, and governor pressure. The governor pressure is a variable pressure input to the valve
body and is one of the signals that a shift is necessary. First through fourth gear are obtained by selectively apply-
ing and releasing the different clutches and bands. Engine power is thereby routed to the various planetary gear
assemblies which combine with the overrunning clutch assemblies to generate the different gear ratios. The torque
converter clutch is hydraulically applied and is released when fluid is vented from the hydraulic circuit by the torque
converter control (TCC) solenoid on the valve body. The torque converter clutch is controlled by the Powertrain
Control Module (PCM). The torque converter clutch engages in fourth gear,and in third gear under various condi-
tions, such as when the O/D switch is OFF, when the vehicle is cruising on a level surface after the vehicle has
warmed up. The torque converter clutch can also be engaged in the MANUAL SECOND gear position if high trans-
mission temperatures are sensed by the PCM. The torque converter clutch will disengage momentarily when an
increase in engine load is sensed by the PCM, such as when the vehicle beginsto go uphill or the throttle pressure
is increased. The torque converter clutch feature increases fuel economyand reduces the transmission fluid tem-
perature.
Since the overdrive clutch is applied in fourth gear only and the direct clutch is applied in all ranges except fourth
gear, the transmission operation for park, neutral, and first through third gear will be described first. Once these
powerflows are described, the third to fourth shift sequence will be described.
PARK POWERFLOW
As the engine is running and the crankshaft is rotat-
ing, the flexplate and torque converter, which are also
bolted to it, are all rotating in a clockwise direction as
viewed from the front of the engine. The notched hub
of the torque converter is connected to the oil pump’s
internal gear, supplying the transmission with oil pres-
sure. As the converter turns, it turns the input shaft in
a clockwise direction. As the input shaft is rotating, the
front clutch hub-rear clutch retainer and all their asso-
ciated parts are also rotating, all being directly con-
nected to the input shaft. The power flow from the
engine through the front clutch hub and rear clutch
retainer stops at the rear clutch retainer. Therefore, no
power flow to the output shaft occurs because no
clutches are applied. The only mechanism in use at
this time is the parking sprag (1), which locks the
parking gear (2) on the output shaft (3) to the trans-
mission case.
pressure to the overdrive clutch during 3-4 upshifts, and when accelerating in fourth gear. The 3-4 accumulator
cushions overdrive clutch engagement to smooth 3-4 upshifts. The accumulator is charged at the same time as
apply pressure acts against the overdrive piston.
DIAGNOSIS AND TESTING
AUTOMATIC TRANSMISSION
Automatic transmission problems can be a result of poor engine performance, incorrect fluid level, incorrect linkage
or cable adjustment, band or hydraulic control pressure adjustments, hydraulic system malfunctions or electrical/
mechanical component malfunctions. Begin diagnosis by checking the easily accessible items such as: fluid level
and condition, linkage adjustments and electrical connections. A road test will determine if further diagnosis is nec-
essary.
PRELIMINARY
Two basic procedures are required. One procedure for vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVEABLE
1. Check for transmission fault codes using DRBscan tool.
2. Check fluid level and condition.
3. Adjust throttle and gearshift linkage if complaint was based on delayed, erratic, or harsh shifts.
4. Road test and note how transmission upshifts, downshifts, and engages.
5. Perform hydraulic pressure test if shift problems were noted during roadtest.
6. Perform air-pressure test to check clutch-band operation.
VEHICLE IS DISABLED
1. Check fluid level and condition.
2. Check for broken or disconnected gearshift or throttle linkage.
3. Check for cracked, leaking cooler lines, or loose or missing pressure-port plugs.
4. Raise and support vehicle on safety stands, start engine, shift transmission into gear, and note following:
a. If propeller shaft turns but wheels do not, problem is with differentialor axle shafts.
b. If propeller shaft does not turn and transmission is noisy, stop engine.Remove oil pan, and check for debris.
If pan is clear, remove transmission and check for damaged drive plate, converter, oil pump, or input shaft.
c. If propeller shaft does not turn and transmission is not noisy, perform hydraulic-pressure test to determine if
problem is hydraulic or mechanical.
ROAD TESTING
Before road testing, be sure the fluid level and control cable adjustmentshave been checked and adjusted if nec-
essary. Verify that diagnostic trouble codes have been resolved.
Observe engine performance during the road test. A poorly tuned engine will not allow accurate analysis of trans-
mission operation.
Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage.
Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means clutch, band or overrunning clutch problems. If the condition is
advanced, an overhaul will be necessary to restore normal operation.
A slipping clutch or band can often be determined by comparing which internal units are applied in the various gear
ranges. The Clutch and Band Application chart provides a basis for analyzing road test results.
Clutch and Band Application Chart
3. Lower vehicle.
4. Turn OD switch on.
5. Secure test gauge so it can be viewed from drivers seat.
6. Start engine and shift into D range.
7. Increase vehicle speed gradually until 3-4 shift occurs and note gauge pressure.
8. Pressure should be 524-565 kPa (76-82 psi) with closed throttle and increase to 690-896 kPa (100-130 psi) at
1/2to3/4throttle.Notethatpressurecanincreasetoaround965kPa(140psi) at full throttle.
9. Return to shop or move vehicle off chassis dyno.
PRESSURE TEST ANALYSIS CHART
TEST CONDITION INDICATION
Line pressure OK during any one test Pump and regulator valve OK
Line pressure OK in R but low in D, 2, 1 Leakage in rear clutch area (seal rings, clutch seals)
Pressure low in D Fourth Gear Range Overdrive clutch piston seal, or check ball problem
Pressure OK in 1, 2 but low in D3 and R Leakage in front clutch area
Pressure OK in 2 but low in R and 1 Leakage in rear servo
Front servo pressure in 2 Leakage in servo; broken servo ring or cracked servo
piston
Pressure low in all positions Clogged filter, stuck regulator valve, wornor faulty
pump, low oil level
Governor pressure too high at idle speed Governor pressure solenoid valvesystem fault. Refer
to diagnostic book.
Governor pressure low at all mph figures Faulty governor pressure solenoid, transmission
control module, or governor pressure sensor
Lubrication pressure low at all throttle positions Clogged fluid cooler or lines, seal rings leaking, worn
pump bushings, pump, clutch retainer, or clogged filter.
Line pressure high Output shaft plugged, sticky regulator valve
Line pressure low Sticky regulator valve, clogged filter, worn pump
AIR TESTING TRANSMISSION CLUTCH AND BAND OPERATION
Air-pressure testing can be used to check transmis-
sion front/rear clutch and band operation. The test can
be conducted with the transmission either in the vehi-
cle or on the work bench, as a final check, after over-
haul.
Air-pressure testing requires that the oil pan and valve
body be removed from the transmission. The servo
and clutch apply passages are shown.
5. Install new pump seal, O-ring, and gasket. Replace oil pump if cracked, porous or damaged in any way. Be sure
to loosen the front band before installing the oil pump, damage to the oil pump seal may occur if the band is still
tightened to the frontclutch retainer.
6. Loosen kickdown lever pin access plug three turns. Apply Loctite™ 592, orPermatex
No. 2 to plug threads and
tightenplugto17Nꞏm(150in.lbs.)torque.
7. Adjust front band.
8. Lubricate pump seal and converter hub with transmission fluid or petroleum jelly and install converter.
9. Install transmission and converter housing dust shield.
10. Lower vehicle.
DIAGNOSIS CHARTS
The diagnosis charts provide additional reference when diagnosing a transmission fault. The charts provide general
information on a variety of transmission, overdrive unit and converter clutch fault conditions.
The hydraulic flow charts in the Schematics and Diagrams section of this group, outline fluid flow and hydraulic
circuitry. Circuit operation is provided for PARK, NEUTRAL, FIRST, SECOND, THIRD, FOURTH, MANUAL FIRST,
MANUAL SECOND, and REVERSE gear ranges. Normal working pressures are alsosupplied for each of the gear
ranges.
Diagnosis Charts
CONDITION POSSIBLE CAUSES CORRECTION
HARSH ENGAGEMENT
(FROM NEUTRAL TO
DRIVE OR REVERSE)1. Fluid Level Low. 1. Add Fluid
2. Throttle Linkage Mis-adjusted.
V- 1 0 O n l y2. Adjust linkage - setting may be too long.
3. Mount and Driveline Bolts Loose. 3. Check engine mount, transmission
mount, propeller shaft, rear spring to body
bolts, rear control arms, crossmember and
axle bolt torque. Tighten loose bolts and
replace missing bolts.
4. U-Joint Worn/Broken. 4. Remove propeller shaft and replace
U-Joint.
5. Axle Backlash Incorrect. 5. Check per Service Manual. Correct as
needed.
6. Hydraulic Pressure Incorrect. 6. Check pressure. Remove, overhaul or
adjust valve body as needed.
7. Band Mis-adjusted. 7. Adjust rear band.
8. Valve Body Check Balls Missing. 8. Inspect valve body for proper check ball
installation.
9. Axle Pinion Flange Loose. 9. Replace nut and check pinion threads
before installing new nut. Replace pinion
gear if threads are damaged.
10. Clutch, band or planetary
component damaged.10. Remove, disassemble and repair
transmission as necessary.
11. Converter Clutch Faulty. 11. Replace converter and flush cooler and
line before installing new converter.
CONDITION POSSIBLE CAUSES CORRECTION
DELAYED ENGAGEMENT
(FROM NEUTRAL TO
DRIVE OR REVERSE)1. Fluid Level Low. 1. Correct level and check for leaks.
2. Filter Clogged. 2. Change filter.
3. Gearshift Linkage Mis-adjusted. 3. Adjust linkage and repair linkage ifworn
or damaged.
4. Torque Converter Drain Back (Oil
drains from torque converter into
transmission sump).4. If vehicle moves normally after 5
seconds after shifting into gear, no repair is
necessary. If longer, inspect pump bushing
for wear. Replace pump house.
5. Rear Band Mis-adjusted. 5. Adjust band.
6. Valve Body Filter Plugged. 6. Replace fluid and filter. If oil pan and old
fluid were full of clutch disc material and/or
metal particles, overhaul will be necessary.
7. Oil Pump Gears Worn/Damaged. 7. Remove transmission and replace oil
pump.
8. Governor Circuit and Solenoid
Valve Electrical Fault.8. Test with DRB
scan tool and repair as
required.
9. Hydraulic Pressure Incorrect. 9. Perform pressure test, remove
transmission and repair as needed.
10. Reaction Shaft Seal Rings
Worn/Broken.10. Remove transmission, remove oil pump
and replace seal rings.
11. Rear Clutch/Input Shaft, Rear
Clutch Seal Rings Damaged.11. Remove and disassemble transmission
and repair as necessary.
12. Regulator Valve Stuck. 12. Clean.
13. Cooler Plugged. 13. Transfer case failure can plug cooler.
NO DRIVE RANGE
(REVERSE OK)1. Fluid Level Low. 1. Add fluid and check for leaks if drive is
restored.
2. Gearshift Linkage/Cable
Loose/Misadjusted.2. Repair or replace linkage components.
3. Rear Clutch Burnt. 3. Removeand disassemble transmission
and rear clutch and seals. Repair/replace
worn or damaged parts as needed.
4. Valve Body Malfunction. 4. Remove and disassemble valve body.
Replace assembly if any valves or bores
are damaged.
5. Transmission Overrunning Clutch
Broken.5. Remove and disassemble transmission.
Replace overrunning clutch.
6. Input Shaft Seal Rings Worn/
Damaged.6. Remove and disassemble transmission.
Replace seal rings and any other worn or
damaged parts.
7. Front Planetary Failed Broken. 7. Remove and repair.
CONDITION POSSIBLE CAUSES CORRECTION
NO DRIVE OR REVERSE
(VEHICLE WILL NOT
MOVE)1. Fluid Level Low. 1. Add fluid and check for leaks if drive is
restored.
2. Gearshift Linkage/Cable
Loose/Misadjusted.2. Inspect, adjust and reassemble linkage
as needed. Replace worn/damaged parts.
3. U-Joint/Axle/Transfer Case
Broken.3. Perform preliminary inspection procedure
for vehicle that will not move. Refer to
procedure in diagnosis section.
4. Filter Plugged. 4. Remove and disassemble transmission.
Repair or replace failed components as
needed. Replace filter. If filter and fluid
contained clutch material or metal particles,
an overhaul may be necessary. Perform
lube flow test. Flush oil. Replace cooler as
necessary.
5. Oil Pump Damaged. 5. Perform pressure test to confirm low
pressure. Replace pump body assembly if
necessary.
6. Valve Body Malfunctioned. 6. Check and inspect valve body. Replace
valve body (as assembly) if any valve or
bore is damaged. Clean and reassemble
correctly if all parts are in good condition.
7. Transmission Internal Component
Damaged.7. Remove and disassemble transmission.
Repair or replace failed components as
needed.
8. Park Sprag not Releasing - Check
Stall Speed, Worn/Damaged/Stuck.8. Remove, disassemble, repair.
9. Torque Converter Damage. 9. Inspect and replace as required.
SHIFTS DELAYED OR
ERRATIC (SHIFTS ALSO
HARSH AT TIMES)1. Fluid Level Low/High. 1. Correct fluid level and check for leaks if
low.
2. Fluid Filter Clogged. 2. Replace filter. If filter and fluid contained
clutch material or metal particles, an
overhaul may be necessary. Perform lube
flow test.
3. Throttle Linkage Mis-adjusted.
V- 1 0 O n l y3. Adjust linkage as described in service
section.
4. Throttle Linkage Binding. V-10
Only4. Check cable for binding. Check for return
to closed throttle at transmission.
5. Gearshift Linkage/Cable
Mis-adjusted.5. Adjust linkage/cable as described in
service section.
6. Clutch or Servo Failure. 6. Remove valve body and air test clutch,
and band servo operation. Disassemble
and repair transmission as needed.
7. Governor Circuit Electrical Fault. 7. Test using DRB
scan tool and repair as
required.
8. Front Band Mis-adjusted. 8. Adjust band.
9. Pump Suction Passage Leak. 9. Check for excessive foam on dipstick
after normal driving. Check for loose pump
bolts, defective gasket. Replace pump
assembly if needed.