The techniques and procedures for correcting the following types of vibrations are including in the road testing diagnosis:

A few basic concepts must be understood before attempting to diagnose a vibration. As in any diagnostic process, information must be gathered and deciphered, and a correction made based on the results. Road testing and inspecting the vehicle in a manner which systematically eliminates different components, in turn supplements the information received from the customer concerning the complaint. Concentrating efforts on the areas that have not been eliminated will make repairs faster and more effective.

All vehicles produce vibrations. Some vibrations are normal, while others are not. Some vibrations can be repaired, some cannot. The customer's complaint must be duplicated or experienced. The vibration and the cause of the vibration must be evaluated under changing conditions. Otherwise, there is no way to know for sure that you are fixing what the customer would like fixed.

The symptoms and characteristics of a noise or vibration are also important information. Ask yourself the following questions before you begin:

Different types of noise and vibration have particular characteristics. These characteristics will help determine the cause of the condition, and the best way to correct the condition. This is the reason for duplicating the vibration.

The first step in diagnosing a vibration complaint is identifying the exact vibration that the customer is complaining about.

Sometimes the vibration can be duplicated at a given speed. Other vibrations may not be as evident and may require questioning the customer carefully. A road test may need to be performed with the customer in the vehicle in order to point out the specific vibration complaint.

The following questions should be asked when attempting to identify a vibration complaint:

The answers to these questions will help in duplicating and diagnosing the vibration.

If the vibration that has been duplicated is suspected as being normal, compare the vibration with a vehicle that is equipped in the same way. The same equipment should include the following:

Important: Once an attempt has been made to repair what may be a normal condition, the customer will likely be convinced that the vehicle has a problem. Customer satisfaction becomes extremely difficult after this point.

If necessary, make the comparison with the customer present and explain the situation.

The purpose of road testing is to duplicate the vibration complaint and to find any operating conditions that change or eliminate the vibration. Most importantly, road testing will determine whether the vibration is related to the engine speed or the road speed.

In order to complete a quick and accurate road test, install an engine tachometer (such as a scan tool) and the EVA in the vehicle. Place the EVA vibration sensor in a location where the customer's concern can be felt.

After a vibration has been categorized as being engine or vehicle-speed related, the vibration can be broken down further to fit into one of the following three groups of rotating components:

These three groups represent the major areas that can produce vibration complaints. The components in each group are related to each other because they are either bolted or splined together. This means that each group of components rotates at the exact same speed.

These categories can be broken down further in order to identify the exact component responsible for the disturbance. The emphasis is on testing (and more testing) in order to pinpoint the source and to eliminate unnecessary parts replacement.