Diagnostic Starting Point - Vibration Diagnosis and Correction

Vibration Diagnosis, Starting Point, and Correction

The information contained in this Vibration Diagnosis and Correction section is designed to cover various vehicle designs and configurations. Not all content will apply to all vehicles.

Important: The following steps must be completed before using the analysis tables or the symptom tables.


1. Perform the Vibration Analysis - Road Testing (Vibration Analysis - Road Testing) table before using the other Vibration Analysis tables or the Symptom tables in order to effectively diagnose the customer's concern.
The use of Vibration Analysis - Road Testing will first provide duplication of virtually any vibration concern and then identify the correct procedure for diagnosing the area of concern which has been duplicated.
2. Review the following Vibration Diagnostic Process.
3. Review the general descriptions to familiarize yourself with vibration theory and terminology, the J 38792-A , Electronic Vibration Analyzer (EVA) 2 and the J 38792-VS , Vibrate Software. Reviewing this information will help you determine whether the condition described by the customer is a potential operating characteristic or not.
Refer to the following:

* Vibration Theory and Terminology (Vibration Theory and Terminology)
* Electronic Vibration Analyzer (EVA) Description and Operation (Electronic Vibration Analyzer (EVA) Description and Operation)
* Vibrate Software Description and Operation (Vibrate Software Description and Operation)
* Reed Tachometer Description (Reed Tachometer Description)

Vibration Diagnostic Process

Important: Using the following steps of the vibration diagnostic process will help you to effectively narrow-down and pin-point the search for the specific source of a vibration concern and to arrive at an accurate repair.


1. Gather specific information on the customer's vibration concern.
2. Perform the road testing steps in sequence as identified in Vibration Analysis - Road Testing in order to duplicate the customer's concern and evaluate the symptoms of the concern under changing conditions. Observe what the vibration feels like and what it sounds like. Observe when the symptoms first appear, when they change, and when they cease.
3. Determine if the customer's vibration concern is truly an abnormal condition or something that is potentially an operating characteristic of the vehicle.
4. Systematically eliminate or "rule-out" possible vehicle systems.
5. Focus diagnostic efforts on the remaining vehicle system and systematically eliminate or "rule-out" possible components of that system.
6. Make a repair on the remaining component, or components, which have not been eliminated systematically, and must therefore be the cause of the vibration.
7. Verify that the customer's concern has been eliminated or at least brought to an acceptable level.
8. Again perform the road testing steps in sequence as identified in Vibration Analysis - Road Testing in order to verify that the vehicle did not have more than one vibration occurring.

Preliminary Visual/Physical Inspection

* Inspect for aftermarket equipment and modifications which could affect the operation of the vehicle rotating component systems.
* Inspect the easily accessible or visible components of the vehicle rotating component systems for obvious damage or conditions which could cause the symptom.
* Inspect the tire inflation pressures for the proper pressure.

Diagnostic Aids

Improper component routing or isolation, or components which are worn or faulty may be the cause of intermittent conditions that are difficult to duplicate. If the vibration concern could not be duplicated by following the steps of the Vibration Diagnostic Process, refer to Vibration Diagnostic Aids (Vibration Diagnostic Aids).