THM 440-T4 Automatic Transaxle, Replaced By Hydra-Matic Division Through the Transaxle Exchange Program
SUBJECT: DEALER AUTHORIZED REPAIRS ON THM 440-T4 TRANSAXLES PLUS ADDITIONAL PROCEDURE INFORMATIONMODELS AFFECTED: ALL 1985 CENTURYS & ELECTRAS EQUIPPED WITH THM 440-T4 TRANSAXLES
Since the introduction of the THM 440-T4 automatic transaxle, some units have been replaced by Hydra-matic Division through the Transaxle Exchange Program. Effective immediately, the dealer technician is to perform on-car service to units that may exhibit any of the conditions listed below:
^ Shift conditions related to vacuum.
^ [1][2]Torque converter clutch does not release, causing engine to stop running.
^ Unit will not upshift or upshifts late.
^ Fluid leaks.
^ Slips on upshift, freewheels, vibrates during acceleration.
^ Harsh 3-2 downshift.
These conditions are to be repaired on-car (transaxle removal not required) by following the on-car service information contained here and referring to Section 7-A and the 440-T4 unit repair portion of the service manual. Perform only the service operations specified. At no time should the transaxle channel plate be removed!
IMPORTANT! REPLACEMENT UNITS WILL BE PROVIDED FOR TRANSAXLES THAT EXHIBIT ANY CONDITIONS NOT LISTED IN THIS BULLETIN.
The following service information is contained in this bulletin:
A. PRELIMINARY CHECK PROCEDURES;
B. DIAGNOSTIC INFORMATION INCLUDING THE FOLLOWING CONDITIONS:
1. Vacuum related shift conditions.
2. [1][2]Torque converter clutch will not release, causing engine to stop running.
3. Transaxle does not upshift or upshifts late.
4. Fluid leaks.
5. Slips on upshifts and downshifts; freewheels; vibration on acceleration.
6. Harsh 3-2 downshift.
C. ADDITIONAL ON-CAR SERVICE PROCEDURES.
Before servicing these, or any other conditions, complete the following Preliminary Check Procedure.
PRELIMINARY CHECK PROCEDURE
Check the transaxle fluid to make sure that it is at the proper level. Note the fluid color. Burned fluid loses its red color and has an acrid odor.
NOTICE: IF THE OIL IS BURNED AND/OR CLUTCH PLATE MATERIAL IS FOUND IN THE OIL PAN, REQUEST A REPLACEMENT TRANSAXLE.
CHECK AND ADJUST T.V. CABLE
CHECK OUTSIDE MANUAL LINKAGE AND CORRECT CHECK ENGINE TUNE* INSTALL OIL PRESSURE GAGE** CONNECT TACHOMETER TO ENGINE
CHECK OIL PRESSURES IN THE FOLLOWING MANNER:
Minimum Line Pressure Check With the parking brake and vehicle brakes applied, take the line pressure readings in the ranges and at the engine r.p.m.'s indicated in the chart below.
Full Line Pressure Check Full line pressure readings are obtained by removing the vacuum line from modulator, and with the parking brake and vehicle brakes applied, take the line pressure readings in the ranges and at the engine r.p.m.'s indicated in the chart below.
NOTICE Total running time not to exceed 2 minutes.
CAUTION Brakes must be applied at all times.
TRANSMISSION LINE PRESSURE:
Line pressure is basically controlled by pump output and the pressure regulator valve. In addition, line pressure is boosted in Reverse, and Lo by the reverse boost valve.
Also, in the Neutral, Drive and Reverse positions of the selector lever, the line pressure should increase with throttle opening because of the vacuum modulator.
*The VRV Valve on Diesel engines must operate properly.
Refer to the appropriate service manual section for complete service procedures. Do not attempt to repair porous or cracked cases.
Diagnostic Diagram Chart:
^ DIAGNOSTIC INFORMATION - BASED ON CONDITION
Vacuum related shift conditions include the following:
^ Harsh neutral to reverse
^ Harsh or firm upshifts
^ 2nd gear starts
^ Harsh 3-2 coast-down shifts
^ Rough 4-3 and 3-2 manual downshifts
^ Slipping in drive or reverse
^ Rough 1-2 shifts
^ Erratic shifts
^ Harsh park to reverse
Diagnostic Procedure Flow Chart:
CONDITIONS INSPECTION PROCEDURES
TRANSAXLE CONVERTER Inspect valve body for foreign material in
CLUTCH WILL NOT converter clutch apply valve..
RELEASE, CAUSES ENGINE TO STOP RUNNING
STUCK IN FIRST, NO UPSHIFT; NO 2ND GEAR; LATE UPSHIFT
LEAKS A. Inspect oil pan and gaskets making certain
screws are properly torqued.
B. Inpsect side cover for cracks, leaking gaskets, and proper screw torque.
C. Check bolt torque on the governor cover. Check "O" ring groove for porosity.
D. Inspect speedo "O" ring.
E. Check right and left axle seals for cuts, cracks or missing garter spring.
F. Inspect servo cover for damage and porosity.
G. Inspect electrical connector and electrical connector "O" ring seal for damage.
LEAKS H. Inspect modulator "O" ring for nicks or
(Continued) cuts.
I. Inspect the fill tube for cracks.
J. Inspect throttle valve (T.V.) cable, "O" rings and case bore for scoring or porosity.
K. Inspect line and governor oil pressure plugs to make certain they are properly torqued and that they are not cross threaded.
L. Inspect the cooler line fittings or cooler and make certain they are not blocked or restricted; check the cooler lines for corrosion. Make certain the lines are installed properly and not damaged.
TORQUE CONVERTER An engine miss condition resulting from a
CLUTCH (T.C.C.) cause such as a cracked spark plug or
SHUDDER faulty injector may be misdiagnosed as a
TCC shudder condition. Verify that engine is operating properly. If shudder condition still exists, contact Technical Assistance Center for an exchange unit.
HARSH 3-2 DOWNSHIFT A revised calibration 3-2 downshift spring
AT 25-35 MPH for the valve body may be obtained from the
Technical Assistance Center to correct this condition. Provide model number and Julian date of transmission. Dealer Technical Bulletin 85-7-1 explains transaxle identification of this information.
The following is a list of the parts that can be serviced on car (attaching screws, bolts and conical washers are not included). The part reference number, following the part name, is the same number found in the service manual 440-T4 section, pages 440-T4-24 and 25, and the parts illustration.
MODULATOR..................#19 MAGNET ............................#66
MODULATOR "O" RING ...........#18 TRANS. OIL PAN.................... #59
MODULATOR RETAINER .......... #20 TRANS. OTL PAN GASKET .............#63
MODULATOR BOLT .............. #21 FILTER ASSEMBLY ...................#58
MODULATOR VALVE.............. #17 GOVERNOR OIL PIPE RETAINER........#129
GOVERNOR COVER ............... #9 GOVERNOR RETAINER GASKET..........#128
GOVERNOR COVER "O" RING........#8 GOVERNOR FEED SCREEN .............#126
GOVERNOR THRUST BEARING .......#7 GOVERNOR FEED PIPE ...............#125
SPEEDO DRIVE GEAR .............#6 GOVERNOR RETURN PIPE .............#124
GOVERNOR ASSEMBLY .............#5 LUBE PIPE - FINAL DRIVE...........#123
SIDE COVER ...................#51 ACCUMULATOR COVER.................#121
SIDE COVER GASKET ............#64 F.D. LUBE PIPE BRACKET ...........#143
SIDE COVER/CHANNEL PLATE .....#65 ACCUMULATOR COVER GASKETS.........#119
OIL PUMP ASSEMBLY ............#44 ACCUMULATOR COVER SPACER PLATE ...#120
(and related sub-assemblies) ACCUMULATOR PINS .......... #111 & 115
T.V. LEVER & BRACKET ASM # 50 1-2 ACCUMULATOR SPRING..........#116
T.V. LINK ....................#49 ACCUMULATOR PISTON SEALS .........#117
SERVO PIPE RETAINER .........#133 1-2 PISTON .......................#118
CONTROL VALVE ASSEMBLY........#35 3-4 ACCUMULATOR SPRING............#112
ALIGNMENT SLEEVE ............#406 3-4 ACCUMULATOR PISTON ...........#114
DETENT SPRING & ROLLER ASM...#707 DRIVE SPROCKET SUPPORT LUBE PIPE..#110
T.C.C. WIRING HARNESS ....... #61 LUBE PIPE RETAINER ...............#109
CLIPS (harness) .........#62 & 67 LUBE PIPE RETAINER "O" RING.......#108
CASE CONNECFOR .............. #23 OIL SCOOP ........................#106
CASE CONNECTOR "O" RING.......#18 1-2 SERVO BRACKET ................#148
SOLENOID ASSEMBLY ...........#328 COOLER CONNECIORS...........#526 & 569
SOLENOID "O" RING............#329 THERMO ELEMENT ..........#102 thru 105
SPACER PLATE ................ #31 AXLE OIL SEALS .............#405 & 540
SPACER PLATE, GASKET C/P......#30 VENT ASSEMBLY ................... #528
SPACER PLATE GASKET S.P./V.B..#32 PIPE PLUG ........................#529
OIL PUMP DRIVE SHAFT..........#29 O.P. DRIVE SHAFT "O" RING.....#28
Refer to Section 7-A in the service manual for the appropriate service procedures.
NOTICE: If repairs require removal or disassembly of the channel plate, the transaxle must be removed and replaced with an exchange unit.
Exchange units may be obtained by contacting the Technical Assistance Center and providing the following information:
1. Vehicle Identification Number
2. Transmission Serial Number (located on a riveted plate under the transmission near RH axle opening)
3. Transmission Pressure Readings
4. Vacuum Pressure at Modulator
5. Vehicle Mileage
6. Dealership Name and Dealer Code
7. Contact Person at Dealership
8. Dealership Phone Number and Mailing Address