The rear latch on the sliding door window on 1985-1987 M Vans may self release when the vehicle is driven over rough roads or when the sliding door is being closed.
This condition is due to mislocated latch attachment holes in the glass and can be corrected by shimming the upper two latch to door attachment screws 2mm. The shims should be installed between the latch and door as shown in Figure No. 1
Starting with 1987 GMC VIN breakpoint HB504511 and Chevrolet VIN breakpoint HB118410, the corrected glass has been incorporated into production.
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.