SUMMARY OF SHUDDER THM 440-T4 DIAGNOSIS-POTENTIAL CAUSES. Buick Skyhawk 1986

For 1990-2009 cars

# SUMMARY OF SHUDDER THM 440-T4 DIAGNOSIS-POTENTIAL CAUSES

#### MODELS AFFECTED: ALL THM 440-T4 TRANSAXLES

#### NOTE: This bulletin supplements 85-7440-6 and 86-7440-2.

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 information.

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

Engine Ignition System Improper operation. Includes items such as fouled or broken spark plugs. TCC APPLY SHUDDER Torque Converter Cover Dimpling caused by too-long bolts (Max. length 15 mm). Torque Converter See NOTE, following chart. TCC APPLY SHUDDER OR Turbine Shaft Seals Missing or damaged. CROWD SHUDDER (Crowd TCC Accumulator Piston Cut or rolled. Refer shudder occurs after Seal to 85-7440-6.

TCC apply, when TCC Solenoid O-Ring Cut or broken. accelerator is Valve Body Gasket Torn or mispositioned. depressed)

TCC CROWD SHUDDER Downshift Delay Module Improper operation. (Canadian 2.8 LE2 Only)

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

2-3 SHIFT SHUDDER Servo Release Pipe Seals Cut Seals. Refer to SHUDDER UNDER LOAD OR Right Rear Engine Mount 86-7440-2. Engine ACCELERATION (1986 3.8L H-Body Only) grounding out.

NO TCC APPLY, DELAYED TCC Solenoid Apply Valve, Sticking in valve body. TCC RELEASE, OR TCC TCC Pressure Regulator (At start of production APPLY AND/OR RELEASE Valve Or Spring 1986,the TCC regulator SHUDDER valve spring was eliminated on the following models: AAH, ACH, ADH, AFH, AMH, ARH, BHH, CFH, CHH, CMH, CNH, HBH, and HJH.) SHUDDER IN REVERSE Right Rear Engine Mount Engine grounding out. (1986 E-Body)

#### 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.

#### MODEL TORQUE CONVERTER PART NUMBER ----- ---------------------------- 4CW, 5CM, 5CN, 5CP, 5CW, 5HA, 5HJ, 5HT, 8656920 6CFH, 6CMH, 6CNH, 6HBH, 6HJH

4BC, 5BA, 5BC, 5BN, 5BR, 6BDH, 6BLH, 8656921 6BMH, 6BTH, 6BVH, 6BZH

6BBH 8656922 5BS, 5BU, 6BHH 8656923 5BX, 6BAH, 6BCH, 6BSH 8656924

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.