Engine - Diagnosing Vibration

89Chevy29

GMC NUMBER: 90-T-04


GROUP: 6A - Engine Mechanical

DATE: July, 1989


CORPORATE
NUMBER: 966105R
SUBJECT: DIAGNOSING ENGINE VIBRATION (VERIFY TRANSMISSION MOUNTS)

MODELS: 1988 - 90 C1, C2, C3 WITH 4.3L, 5.0L, 5.7L AND ALL A/T AND M/T

Figure 1:

Figure 2:

Figure 3:

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. 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 used in the mounts has 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.