DIAGNOSING ENGINE VIBRATION (VARIFY TRANSMISSION MOUNTS)

VEHICLES AFFECTED: 1988-90 C1, C2, C3 W/4.3L ,5.0L, 5.7L AND ALL A/T AND M/T

This bulletin is for information purposes only, and should be used as a guideline for correctly identifying transmission mounts on light duty C trucks with gas engines and all automatic and manual transmissions.

When diagnosing 1988-90 Light Duty 'C' Trucks for engine vibration, the transmission mount should be inspected to make sure it is the correct application for the mount. The rubber in the mounts uses different durometer ratings, and the incorrect mount could induce a vibration that may not be there if the correct mount is installed.

All the mounts can be visibly identified, and Figures 1-3 show the correct applications for the mounts.

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.