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Transmission and transfer case » AW-4 automatic transmission » Diagnosis and testing
Service diagnosis

DIAGNOSIS TABLE

CONDITION

POSSIBLE CAUSE

CORRECTION

VEHICLE WILL NOT BACK UP OR MOVE FORWARD Shift cable out of adjustment or damaged
Valve body or primary regulator faulty
Park lock pawl faulty
Torque converter faulty
Converter drive plate broken
Oil pump intake screen blocked
Transmission faulty
Adjust cable or replace cable
Inspect/repair valve body
Repair park pawl
Replace torque converter
Replace drive plate
Clean screen
Disassemble and repair transmission
SHIFT LEVER POSITION INCORRECT Shift cable out of adjustment
Manual valve and lever faulty
Adjust cable
 Repair valve body
HARSH ENGAGEMENT Throttle cable out of adjustment
Valve body or primary regulator faulty
Accumulator pistons faulty
Transmission faulty
Adjust throttle cable
Repair valve body
Repair pistons
Disassemble and repair transmission
DELAYED 1-2, 2-3 OR 3-4 UP-SHIFT, OR DOWN-SHIFTS FROM 4-3 OR 3-2 AND SHIFTS BACK TO 4 OR 3 Electronic control problem
Valve body faulty
Solenoid faulty
Locate problem with DRB Tester
Repair valve body
 Repair solenoid
SLIPS ON 1-2, 2-3 OR 3-4 UP-SHIFT, OR SLIPS OR SHUDDERS DURING ACCELERATION Shift cable out of adjustment
Throttle cable out of adjustment 
Valve body faulty 
Solenoid faulty 
Transmission faulty
Adjust cable
Adjust cable
Repair valve body
Replace solenoid
Disassemble and repair
transmission
DRAG OR BIND ON 1-2, 2-3 OR 3-4 UP-SHIFT Shift cable out of adjustment
Valve body faulty
Transimssion faulty
 Adjust cable
 Repair valve body
 Disassemble and repair transmission
CONVERTER CLUTCH DOES NOT ENGAGE IN 2ND, 3RD OR 4TH Electronic control problem
Valve body faulty
Solenoid faulty
Transmission faulty
Check with DRB Tester
Repair valve body
Replace solenoid
Disassemble and repair transmission
HARSH DOWN-SHIFT Throttle cable out of adjustment
Throttle cable and cam faulty
Accumulator pistons faulty
Valve body faulty
Transmission faulty
Adjust cable
 Replace cable and cam
Repair pistons
Repair valve body
Disassemble and repair transmission
NO DOWN-SHIFT WHEN COASTING Valve body faulty
Solenoid faulty
Electronic control problem
Repair valve body
Replace solenoid
Locate problem with DRB Tester
DOWN-SHIFT LATE OR EARLY DURING COAST Throttle cable faulty
Valve body faulty
Transmission faulty
Solenoid faulty
Electronic control problem
 Replace cable
Repair valve body
Disassembly and repair transmission
 Replace solenoid
Locate problem with DRB Tester
NO 4-3, 3-2 OR 2-1 KICKDOWN Solenoid faulty
Electronic control problem
Valve body faulty
Replace solenoid
 Locate problem with DRB Tester
Repair valve body
NO ENGINE BRAKING IN 1-2 POSITION Solenoid faulty
Electronic control problem
Valve body faulty
Transmission faulty
Replace solenoid
Locate problem with DRB Tester
Repair valve body
Disassemble and repair transmission
VEHICLE DOES NOT HOLD IN PARK Shift cable out of adjustment
Parking lock pawl cam and spring faulty
 Adjust cable
Replace cam and spring
OVERHEAT DURING NORMAL OPERATION (FLUID DISCOLORED, SMELLS BURNED) Low fluid level
Fluid cooler, lines blocked, or cooler cracked (oil in engine coolant)
Add fluid and check for leaks
Flush cooler and lines and replace radiator if transmission fluid has entered coolant
OVERHEAT DURING COMMERCIAL OPERATION OR WHILE TRAILE TOWING (FLUID DARK AND BURNED WITH SOME SLUDGE FORMATION) Vehicle not properly equipped for trailer towing or commercial use
Vehicle not equipped with auxiliary fluid cooler
Extensive idling time or operation in heavy traffic in hot weather
Tow vehicle overloaded (exceeding vehicle tow capacity
Air flow to auxiliary cooler blocked by snow plow, front mounted spare tire, bug screen, or similar item
Be sure vehicle is equipped with recommended optional components (i.e. HD springs, transmission, axle, larger CID engine, auxiliary cooler, correct axle ratio, etc.). If vehicle is not so equipped, it should not be used for severe service operation
Drain fluid, change filter, and install auxiliary cooler
Cut down on idling time; shift into neutral every so often and run engine at 1000 rpm to help circulate fluid through cooler
Be sure vehicle is properly equipped to handle load; do not tow Class III-type loads with a vehicle that is only rated for Class I or II operation Remove or reposition item causing air flow blockage
OIL COMES OUT FILLER TUBE Transmission overfilled
Breather vent in oil pump blocked
Fluid cooler or cooler lines plugged
Drain fluid to correct level; remove neutral switch and drain through switch hole with suction gun
 Inspect and clear blockage
Flush cooler and lines
    More about «Diagnosis and testing»:

    General diagnosis information

    Effects of incorrect fluid level

    Causes of burnt fluid

    Fluid contamination

    Preliminary inspection and adjustment

    Manual shifting test

    Hydraulic pressure test

    Pressure test analysis

    Time lag test

    Test procedure

    Time lag test analysis

    Service diagnosis

    Transmission solenoid testing

    Park/neutral position switch

    Gearshift cable

    Throttle valve cable

    Speed sensor testing

    Flow testing transmission main cooler

    Torque converter stator clutch inspection

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