Vehicle Preparation

1. Check and verify if the vehicle is equipped with original equipment, type, size, and brand wheels and tires. If non-original equipment wheels and/or tires are installed, it may be necessary to substitute original equipment tire/wheel assemblies.
2. Check and set tire pressure.
3. Secure any externally mounted accessories such as luggage racks or any antenna which may cause wind noise that interferes with NVH diagnosis.
4. A tachometer should be used.
5. Note the fuel level. Some vehicles change NVH concerns when the fuel level changes.
6. Try to duplicate the conditions with the customer present, particularly the speed and throttle operation.
7. Find the speed where the concern is most severe.
8. Turn the air conditioning system off and on to isolate air conditioning system impact on the noise. Accelerate gently through the speed to a few mph above and then coast back down a few mph below and note if the concern changes.
9. Repeat this procedure if necessary to get a feeling for the behavior. Then drive about five mph above the speed, put the transaxle in neutral and coast down. Note any change in behavior.
10. Try "floating" the driveline by backing off slightly on the throttle at the problem speed. If the concern does not change in all these modes of operation, the cause may be driveline imbalance since the imbalance is not changed by the throttle position.