SUMMARY OF SHUDDER THM 440-T4 DIAGNOSIS-POTENTIAL CAUSES

MODELS/YEARS: ALL MODELS WITH 440-T4 TRANSAXLE

This bulletin replaces Dealer Technical Bulletin 86-T-51. It contains revised "Year Digit and Model" information and torque converter part numbers.

A vehicle equipped with a 1984 through 1986 THM 440-T4 transaxle may experience a shudder condition which may be described as similar to driving over rough pavement. This condition may be the result of various engine and/or transaxle-related causes.

Before diagnosing for a transaxle-related shudder condition, make sure the condition is not engine-related.

Refer to the chart for diagnosis information and potential causes. When performing any service procedure, refer to the appropriate service manual.

Refer to Figure 1 for transaxle identification.

Note: A 1986 THM 440-T4 transaxle built before March 10, 1986 (Julian date 069) may exhibit a torque converter clutch apply shudder at 45-55 mph.

The shudder condition may be caused by the damper plate not fully seating.

If the TCC apply shudder condition is exhibited and all diagnostic procedures have been performed, replace the torque converter with a service converter as indicated below.

Year Digit and Model Torque Converter Part Number -------------------- ---------------------------- 4CW, 5CM, 5CN, 5CP, 5CW, 8656920 5HA, 5HJ, 5HT, 6CFH, 6CMH, 6CNH, 6HBH, 6HJH

4BC, 5BA, 5BC, 5BN, 5BR, 8656928 6BDH, 6BLH, 6BMH, 6BTH, 6BYH, 6BZH

6BBH 8656931

5BS,5BU,6BHH,5BV 8656923

5BW, 5BX, 6BAH, 6BCH, 6BSH 8656930

CONDITION INSPECT COMPONENT FOR CAUSE --------- ----------------- --------- ENGINE CHUGGLE Engine Fuel Restriction or imbalance. For UNDER LOAD Delivery System example, fouled fuel injectors due to deposits.

Engine Ignition Improper, operation. Includes System items such as fouled or cracked spark plugs.

TCC APPLY SHUDDER Torque Converter Dimpling caused by too-long Cover bolts. (Max. length 15 mm)

Torque Converter Dampener plate not seating properly. Replace converter with new part number listed.

TCC APPLY SHUDDER Turbine Shaft Seals Mining or damaged. OR CROWD SHUDDER (Crowd shudder occurs TCC Accummulator Cut or rolled. Refer to March after TCC apply, when Piston Seal 1985 Service Guild, page 57. accelerator is depressed.) TCC Solenoid 0-ring Cut or broken

Valve Body Gasket Torn or mispositioned

NO TCC APPLY, TCC Solenoid Apply Sticking in valve body. (At DELAYED TCC Valve, TCC Pressure start of production 1986, RELEASE,OR TCC Regulator Valve or the TCC regulator valve spring APPLY AND/OR Spring was eliminated on the following models: AAH, ACH, ADH, RELEASE SHUDDER AFH, AMH, ARH, BHH, CFH, CHH, CMH, CNH, HBH, and HJH.)

1-2 SHIFT SHUDDER 2nd Clutch Plates Replace steel and fiber plates (soak in transaxle fluid for 30 mins. prior to installation).

2-3 SHIFT SHUDDER Servo Release Pipe Cut seals. Refer to DTB 86-T-7. OR FLARE Seals

SHUDDER, VIBRATION Right Rear Engine Improved mount for vibration UNDER LOAD OR Mount (1986 3.8L isolation released. Refer ACCELERATION Delta 88 Only) to DTB 86-T-28.

SHUDDER IN REVERSE Engine Mounts (1986 Engine grounding out. Toronado) Refer to DTB 86-T-40

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.