SHUDDER OR VIBRATION AT LOW SPEEDS (NEW PROM RELEASED)

Subject: SHUDDER OR VIBRATION AT LOW SPEEDS

Model and Year: 1990-92 LUMINA (APV) WITH 3.1L ENGINE

THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN 91-380-6E. THE 1992 MODEL YEARS HAS BEEN ADDED. ALL COPIES OF 91-38O-6E SHOULD BE DISCARDED.

Condition: Some owners of 1990 - 1992 U-vans with 3.1 L (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:

1990 Vehicles

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

1991 and 1992 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.

Labor Operation Number: T0500 Labor Time: .7 Hour

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.