3: Preparing for the Road Test

Observe the following when preparing for the road test:

• Review the information recorded on the NVH Diagnostic Guide. It is important to know the specific concern the customer has with the vehicle.
• Do not be misled by the reported location of the noise/vibration. The cause can actually be some distance away.
• Remember that the vibrating source component (originator) may only generate a small vibration. This small vibration can in turn cause a larger vibration/noise to emanate from another receiving component (reactor) due to contact with other components (transfer path).
• Conduct the road test on a quiet street where it is safe to duplicate the vibration/noise. The ideal testing route is an open, low-traffic area where it is possible to operate the vehicle at the speed at which the condition occurs.
• If possible, lower the radio antenna in order to minimize turbulence. Identify anything that could potentially make noise or be a source of wind noise. Inspect the vehicle for add-on items that create vibration/noise. Turn off the radio and the heating and cooling system blower.
• The engine speed is an important factor in arriving at a final conclusion. Therefore, connect an accurate tachometer to the engine, even if the vehicle has a tachometer. Use a tachometer that has clearly defined increments of less than 50 RPM. This ensures an exact engine speed reading.