K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
Technical Service Bulletin # 891994A
Drivetrain - Evaluating Driveline Vibration
EVALUATING DRIVELINE VIBRATION
Model and Year:
1980-89 LIGHT DUTY TRUCKS
ALL CHEVROLET DEALERS
The purpose of this bulletin is to provide a logical approach to evaluating vehicles for driveline generated vibrations and imbalance occurring between
50-62 mph. The following diagnosis tree is designed to be used as a guide, and when utilized properly can help isolate and identify causes of driveline
Prior to road test, determine if disturbance is engine related by following the procedure below:
With engine at operating temperature and vehicle parked, set parking brake and place transmission shift lever in neutral.
Slowly accelerate engine from idle to 4000 RPM (diesels 3200 RPM), noting RPM at which vibration is felt (if any).
If vibration is felt, disregard use of this bulletin and isolate and repair responsible engine component (transmission, clutch/flywheel, torque
converter, engine accessory, etc.).
Road test vehicle on a smooth level road to verify customer comment. It is usually beneficial to road test the vehicle with the customer present. Note the
speeds and conditions at which the disturbance is most noticeable. Refer to Remark A in this bulletin for diagnosis information.