SURGE WHEN TCC ENGAGES NEW PROM P/N TO REVISE TCC

TORQUE CONVERTER CLUTCH (TCC) "CHUGGLE" OR "SURGE"

MODELS AFFECTED: 1985 & 1986 CENTURYS, SOMERSETS AND SKYLARKS --------------- EQUIPPED WITH 2.5L ENGINES (VIN CODES R & U) AND AUTOMATIC TRANSMISSIONS

Some 1985 and 1986 Centurys, Somersets and Skylarks equipped with 2.5L engines (VIN Codes R and U) may experience a condition described as "chuggle" or "Surge".

If this condition is encountered and cannot be repaired using currently published diagnostic and service information, it may be caused by the torque converter clutch engaging at too low of vehicle speed. This condition will be improved by the installation of a new Service PROM, which contains calibration changes designed to enhance vehicle cold driveability and increase TCC engagement speed to approximately 49 mph.

Refer to the chart below for proper application and Service PROM part number:

SALES PROM ENGINE AXLE OPTION PART APPLICATION CODE RATIO CODE NUMBER ----------- ------- ----- ------ ------ 1985 Century and Skylark R 2.84 F17 1228020 1985 Century and Skylark R 2.39 STD. 1227924 1985 Somerset Regal U 2.84 Only 1228021 1986 Century R 2.84 STD. 1228019 1986 Century R 2.39 F62 1228018 U 2.84 Only 1228017

Use Applicable Labor Time and Labor Operation Number.

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.