DIRECT DRIVE POWERFLOW
The vehicle has accelerated and reached the shift point for the 2-3 upshiftinto direct drive. When the shift takes
place, the front band is released, and the front clutch is applied (1, 9). The rear clutch stays applied (4, 8) as it has
been in all the forward gears. With the front clutch now applied, engine torque is now on the front clutch retainer,
which is locked to the sun gear drivingshell. This means that the sun gear isnow turning in engine rotation (clock-
wise) and at engine speed. The rear clutch is still applied so engine torque(6, 10) is also still on the front annulus
gear. If two members of the same planetary set are driven, direct drive results. Therefore, when two members are
rotating at the same speed and in the same direction, it is the same as being locked up. The rear planetary set is
also locked up, given the sun gear is still the input, and the rear annulus gear must turn with the output shaft (3, 5).
Both gears are turning in the same direction and at the same speed. The frontand rear planet pinions do not turn
at all in direct drive. The only rotation is the input from the engine to the connected parts, which are acting as one
common unit, to the output shaft.
FOURTHGEARPOWERFLOW
Fourth gear overdrive range is electronically controlled and hydraulically activated. Various sensor inputs are sup-
plied to the powertrain control module to operate the overdrive solenoid on the valve body. The solenoid contains a
check ball that opens and closes a vent port in the 3-4 shift valve feed passage. The overdrive solenoid (and check
ball) are not energized in first, second, third, or reverse gear. The vent port remains open, diverting line pressure
from the 2-3 shift valve away from the 3-4 shift valve. The Tow/Haul controlswitch must be in the ON position to
transmit overdrive status to the PCM. A 3-4 upshift occurs only when the overdrive solenoid is energized by the
PCM. The PCM energizes the overdrive solenoid during the 3-4 upshift. Thiscauses the solenoid check ball to close
the vent port allowing line pressure from the 2-3 shift valve to act directly on the 3-4 upshift valve. Line pressure on
the 3-4 shift valve overcomes valve spring pressure moving the valve to theupshift position. This action exposes
the feed passages to the 3-4 timing valve, 3-4 quick fill valve, 3-4 accumulator, and ultimately to the overdrive pis-
ton. Line pressure through the timing valve moves the overdrive piston into contact with the overdrive clutch. The
direct clutch is disengaged before the overdrive clutch is engaged. The boost valve provides increased fluid apply
Direct Drive Powerflow
1 - FRONT CLUTCH APPLIED 6 - INPUT SHAFT
2 - OVER-RUNNING CLUTCH FREE-WHEELING 7 - OVER-RUNNING CLUTCH FREE-WHEELING
3 - OUTPUT SHAFT 8 - REAR CLUTCH APPLIED
4 - REAR CLUTCH APPLIED 9 - FRONT CLUTCH APPLIED
5 - OUTPUT SHAFT 10 - INPUT SHAFT
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.
CONDITION POSSIBLE CAUSES CORRECTION
NO KICKDOWN OR
NORMAL DOWNSHIFT1. Throttle Linkage Mis-adjusted.
V- 1 0 O n l y1. Adjust linkage.
2. Accelerator Pedal Travel
Restricted.2. Verify floor mat is not under pedal, repair
worn accelerator cable or bent brackets.
3. Valve Body Hydraulic Pressures
TooHighorTooLowDuetoValve
Body Malfunction or Incorrect
Hydraulic Control Pressure
Adjustments.3. Perform hydraulic pressure tests to
determine cause and repair as required.
Correct valve body pressure adjustments as
required.
4. Governor Circuit Electrical Fault. 4. Test with DRB
scan tool and repair as
required.
5. Valve Body Malfunction. 5. Perform hydraulic pressure tests to
determine cause and repair as required.
Correct valve body pressure adjustments as
required.
6. TPS Malfunction. 6. Replace sensor, check with DRB
scan
tool.
7. PCM Malfunction. 7. Check with DRB
scan tool and replace
if required.
8. Valve Body Malfunction. 8. Repair sticking 1-2, 2-3 shift valves,
governor plugs, 3-4 solenoid, 3-4 shift
valve, 3-4 timing valve.
STUCK IN LOW GEAR
(WILL NOT UPSHIFT)1. Throttle Linkage Mis-adjusted/
Stuck. V-10 Only1. Adjust linkage and repair linkage if worn
or damaged. Check for binding cable or
missing return spring.
2. Gearshift Linkage Mis-adjusted. 2. Adjust linkage and repair linkage ifworn
or damaged.
3. Governor Component Electrical
Fault.3. Check operating pressures and test with
DRB
scan tool, repair faulty component.
4. Front Band Out of Adjustment. 4. Adjust Band.
5. Clutch or Servo Malfunction. 5. Air pressure check operation of clutches
and bands. Repair faulty component.
CREEPS IN NEUTRAL 1. Gearshift LinkageMis-adjusted. 1. Adjust linkage.
2. Rear Clutch Dragging/Warped. 2. Disassemble and repair.
3. Valve Body Malfunction. 3. Perform hydraulic pressure test to
determine cause and repair as required.
BUZZING NOISE 1. Fluid Level Low 1. Add fluid and check for leaks.
2. Shift Cable Mis-assembled. 2. Route cable away from engine and bell
housing.
3. Valve Body Mis-assembled. 3. Remove, disassemble, inspect valve
body. Reassemble correctly if necessary.
Replace assembly if valves or springs are
damaged. Check for loose bolts or screws.
4. Pump Passages Leaking. 4. Check pump for porous casting, scores
on mating surfaces and excess rotor
clearance. Repair as required. Loose pump
bolts.
5. Cooling System Cooler Plugged. 5. Flow check cooler circuit. Repair as
needed.
6. Overrunning Clutch Damaged. 6. Replace clutch.
CONDITION POSSIBLE CAUSES CORRECTION
3-4 UPSHIFT OCCURS
IMMEDIATELY AFTER 2-3
SHIFT1. Overdrive Solenoid Connector or
Wiring Shorted.1. Test connector and wiring for loose
connections, shorts or ground and repair as
needed.
2. TPS Malfunction. 2. Test TPS and replace as necessary.
Check with DRB
scan tool.
3. PCM Malfunction. 3. Test PCM with DRB
scan tool and
replace controller if faulty.
4. Overdrive Solenoid Malfunction. 4. Replace solenoid.
5. Valve Body Malfunction. 5. Remove, disassemble, clean and inspect
valve body components. Make sure all
valves and plugs slide freely in bores.
Polish valves with crocus cloth if needed.
WHINE/NOISE RELATED
TO ENGINE SPEED1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Shift Cable Incorrect Routing. 2. Check shift cable for correct routing.
Should not touch engine or bell housing.
NO3-4UPSHIFT 1.O/DSwitchInOFFPosition. 1.TurncontrolswitchtoONposition.
2. Overdrive Circuit Fuse Blown. 2. Replace fuse. Determine why fuse failed
and repair as necessary (i.e., shorts or
grounds in circuit).
3. O/D Switch Wire Shorted/Open
Cut.3. Check wires/connections with 12V test
lamp and voltmeter. Repair damaged or
loose wire/connection as necessary.
4. Distance or Coolant Sensor
Malfunction.4. Check with DRB
scan tool and repair or
replace as necessary.
5. TPS Malfunction. 5. Check with DRB
scan tool and replace
if necessary.
6. Neutral Sense to PCM Wire
Shorted/Cut.6. Test switch/sensor as described in
service section and replace if necessary.
Engine no start.
7. PCM Malfunction. 7. Check with DRB
scan tool and replace
if necessary.
8. Overdrive Solenoid Shorted/Open. 8. Replace solenoid if shorted or openand
repair loose or damaged wires (DRB
scan
tool).
9. Solenoid Feed Orifice in Valve
Body Blocked.9. Remove, disassemble, and clean valve
body thoroughly. Check feed orifice.
10. Overdrive Clutch Failed. 10. Disassemble overdrive and repair as
needed.
11. Hydraulic Pressure Low. 11. Pressure test transmission to determine
cause.
12. Valve Body Valve Stuck. 12. Repair stuck 3-4 shift valve, 3-4 timing
valve.
13. O/D Piston Incorrect Spacer. 13. Remove unit, check end play and install
correct spacer.
14. Overdrive Piston Seal Failure. 14. Replace both seals.
15. O/D Check Valve/Orifice Failed. 15. Check for free movement and secure
assembly (in piston retainer). Check ball
bleed orifice.
CONDITION POSSIBLE CAUSES CORRECTION
NO START IN PARK OR
NEUTRAL1. Gearshift Linkage/Cable
Mis-adjusted.1. Adjust linkage/cable.
2. Neutral Sense Wire Open/Cut. 2. Check continuity with test lamp. Repair
as required.
3. Park/Neutral Switch, or
Transmission Range Sensor Faulty.3. Refer to service section for test and
replacement procedure.
4. Park/Neutral Switch, or
Transmission Range Sensor
Connection Faulty.4. Connectors spread open. Repair.
5. Valve Body Manual Lever
Assembly Bent/Worn/Broken.5. Inspect lever assembly and replace if
damaged.
NO REVERSE (OR SLIPS
IN REVERSE)1. Direct Clutch Pack (front clutch)
Worn.1. Disassemble unit and rebuild clutch
pack.
2. Rear Band Mis-adjusted. 2. Adjust band.
3. Front Clutch Malfunctioned/
Burned.3. Air-pressure test clutch operation.
Remove and rebuild if necessary.
4. Overdrive Thrust Bearing Failure. 4. Disassemble geartrain and replace
bearings.
5. Direct Clutch Spring Collapsed/
Broken.5. Remove and disassemble unit. Check
clutch position and replace spring.
CONDITION POSSIBLE CAUSES CORRECTION
OIL LEAKS. 1. Fluid Lines and Fittings Loose/
Leaks/Damaged.1. Tighten fittings. If leaks persist, replace
fittings and lines if necessary.
2. Fill Tube (where tube enters case)
Leaks/Damaged.2. Replace tube seal. Inspect tube for
cracks in fill tube.
3. Pressure Port Plug Loose
Loose/Damaged.3. Tighten to correct torque. Replace plug
or reseal if leak persists.
4. Pan Gasket Leaks. 4. Tighten pan screws (150 in. lbs.). If leaks
persist, replace gasket.
5. Valve Body Manual Lever Shaft
Seal Leaks/Worn.5. Replace shaft seal.
6. Rear Bearing Access Plate Leaks. 6. Replace gasket. Tighten screws.
7. Gasket Damaged or Bolts are
Loose.7. Replace bolts or gasket or tighten both.
8. Adapter/Extension Gasket
Damaged Leaks/Damaged.8. Replace gasket.
9. Park/Neutral Switch, or
Transmission Range Sensor
Leaks/Damaged.9. Replace switch and gasket.
10. Converter Housing Area Leaks. 10. Check for leaks at seal caused by worn
seal or burr on converter hub (cutting seal),
worn bushing, missing oil return, oil in front
pump housing or hole plugged. Check for
leaks past O-ring seal on pump or past
pump-to-case bolts; pump housing porous,
oil coming out vent due to overfill or leak
past front band shaft access plug.
11. Pump Seal Leaks/Worn/
Damaged.11. Replace seal.
12. Torque Converter Weld
Leak/Cracked Hub.12. Replace converter.
13. Case Porosity Leaks. 13. Replace case.
NOISY OPERATION IN
FOURTH GEAR ONLY1. Overdrive Clutch Discs, Plates or
Snap Rings Damaged.1. Remove unit and rebuild clutch pack.
2. Overdrive Piston or Planetary
Thrust Bearing Damaged.2. Remove and disassemble unit. Replace
either thrust bearing if damaged.
3. Output Shaft Bearings Scored/
Damaged.3. Remove and disassemble unit. Replace
either bearing if damaged.
4. Planetary Gears Worn/Chipped. 4. Remove and overhaul overdrive unit.
5. Overdrive Unit Overrunning Clutch
Rollers Worn/Scored.5. Remove and overhaul overdrive unit.
STANDARD PROCEDURE - ALUMINUM THREAD REPAIR
DamagedorwornthreadsinthealuminumtransmissioncaseandvalvebodycanberepairedbytheuseofHeli-
Coils™, or equivalent. This repair consists of drilling out the worn-out damaged threads. Then tap the hole with a
special Heli-Coil™ tap, or equivalent, and installing a Heli-Coil™ insert, or equivalent, into the hole. This brings the
hole back to its original thread size.
Heli-Coil™, or equivalent, tools and inserts are readily available from most automotive parts suppliers.
REMOVAL
NOTE: The overdrive unit can be removed and serviced separately. It is not necessary to remove the entire
transmission assembly to perform overdrive unit repairs.
1. Disconnect battery negative cable.
2. Raise vehicle.
3. Remove the transfer case skid plate (2), if
equipped.
4. Disconnect and lower or remove any necessary
exhaust components.
5. Remove engine-to-transmission struts.
6. Remove starter motor. (Refer to 8 - ELECTRICAL/
STARTING/STARTER MOTOR - REMOVAL)
7. Disconnect and remove the crankshaft position
sensor. (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/CRANKSHAFT POSITION SENSOR -
REMOVAL) Retain the sensor attaching bolts.
8. If transmission is being removed for overhaul,
remove transmission oil pan, drain fluid and rein-
stall pan.
9. Remove torque converter access cover.
10. Rotate crankshaft in clockwise direction until con-
verter bolts are accessible. Then remove bolts
one at a time. Rotate crankshaft with socket
wrench on dampener bolt.
11. Mark propeller shaft and axle yokes for assembly alignment. Then disconnect and remove propeller shaft. On 4
x 4 models, remove both propeller shafts. (Refer to 3 - DIFFERENTIAL & DRIVELINE/PROPELLER SHAFT/
PROPELLER SHAFT - REMOVAL)
12. Disconnect wires from the transmission range sensor and transmissionsolenoid connector.
13. Disconnect gearshift cable (1) from the transmission manual lever (2).
14. For vehicles with gas engines, disconnect throttle valve cable from transmission bracket andthrottle valve lever.
4. Removetheoverdriveunitfromthemaintransmis-
sion case. If overdrive unit is not to be serviced,
install Alignment Shaft 6227-2 into the overdrive
unit to prevent misalignment of the overdrive
clutches during service ofmain transmission com-
ponents.
5. Remove throttle and shift levers from valve body
manual shaft and throttle lever shaft.
6. Remove transmission oil pan and gasket.
7. Remove filter (1) from valve body (2). Keep filter
screws separate from other valve body screws. Fil-
ter screws are longer and should be kept with filter.
8. Remove the transmission range sensor. (Refer to
21 - TRANSMISSION/AUTOMATIC - 48RE/
TRANSMISSION RANGE SENSOR - REMOVAL)
9. Remove hex head bolts (1, 2) attaching valve body
to transmission case. A total of 10 bolts are used.
Note different bolt lengths for assembly reference.
10. Remove valve body assembly (2). Push valve
body harness connector out of case. Then work
park rod (3) and valve body out of case.