SHUDDER/VIBRATION AT LOW SPEED (INSTALL NEW PROM)

SUBJECT: SHUDDER OR VIBRATION AT LOW SPEEDS - INSTALL NEW PROM

MODELS/YEARS: 1990-92 SILHOUETTE WITH 3.1 L (VIN D) ENGINE

THIS BULLETIN CANCELS AND SUPERSEDES DEALER TECHNICAL BULLETIN 90-T-202 WHICH SHOULD BE DISCARDED.

CONDITION: Some owners of 1990-92 Silhouette vans with 3.1L (VIN D) engine may comment of a shudder or vibration at low speeds.

CAUSE: This condition may be caused by the transmission converter clutch being engaged at 23 MPH.

CORRECTION: If normal diagnostic procedures shown in your Service Manual (Section 6E2-B-3) do not correct this condition, a new PROM with a "TCC" (torque converter clutch) engagement speed of 35 MPH is available. The part numbers are as follows:

Emission PROM Scanner Broadcast System Package No. I.D. Code ---------- ----------- -------- ---------- 1990 Vehicles California 16163425 3431 AYAC Federal 16163426 3441 AYAD

1991-92 Vehicles California 16164894 4911 AYHP Federal 16164893 4901 AYHN

NOTE: This correction will have no impact on performance above 35 MPH.

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

Labor Operation Number: T0500 Labor Time: 0.7 hour Trouble Code: 92

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.