Road Test

A vibration diagnostic procedure always begins with a road test. The road test and customer interview (if available) will provide much of the information needed to find the source of a vibration.

During the road test, drive the vehicle on a road that is smooth and free of undulations. If vibration is apparent, note and record the following:
^ The speed at which the vibration occurs.
^ What type of vibration occurs in each speed range-mechanical or audible.
^ How the vibration is affected by changes in engine torque, vehicle speed and engine speed.
^ Type of vibration sensitivity-torque sensitive, vehicle speed sensitive, or engine speed sensitive.

If the road test indicates the vibration is related to the tires or wheels, use the Tire Wear Condition Chart to help pinpoint the cause of the concern. If the road test indicates that there is tire whine but no shake or vibration, the noise originates with the contact between the tire and the road surface.

Use the following explanation of terms to help isolate the source of the vibration.
Torque Sensitive
This means that the condition can be improved or worsened by accelerating, decelerating, coasting or maintaining a steady vehicle speed.
Vehicle Speed Sensitive
This means that the vibration always occurs at the same vehicle speed and is not affected by the application of engine torque, engine speed, or transaxle gear.
Engine Speed Sensitive
This means that the vibration occurs at varying vehicle speeds when a different transaxle gear is selected and the engine speed is constant. It can sometimes be isolated by increasing or decreasing engine speed with the transaxle in NEUTRAL or by stall testing with the transaxle in gear. If the condition is engine-speed sensitive, the condition is not related to tires.

If the road test indicates that there is tire whine, but no shake or vibration, the noise originates with the contact between the tire and the road surface.

A thumping noise usually means that the tire is flat or has soft spots making a noise as they slap the roadway. Tire whine can be distinguished from axle noise. Tire whine remains the same over a range of speeds.