SHUDDER/VIBRATION AT LOW SPEED INSTALL NEW PROM

SUBJECT: SHUDDER OR VIBRATION AT LOW SPEEDS (INSTALL NEW PROM)

VEHICLES AFFECTED: 1990 U-VANS WITH 3.1L

Condition:

------------ Some owners of 1990 U-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 37 kph (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 56 kph (35 MPH) is available. The part numbers are as follows:

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

NOTE: This correction will have no impact on performance above 56 KPH (35 MPH.)

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.