For 1990-2009 cars

Important: If you have not reviewed the Diagnostic Starting Point - Vibration Diagnosis and completed the Vibration Analysis Tables as indicated, refer to Diagnostic Starting Point - Vibration Diagnosis and Correction BEFORE proceeding.

The diagnostic information contained in this Diagnostic Aids section will help you determine the correct course of action to take for the following four main conditions. Refer to the appropriate condition following this list:

• | Vibration NOT Duplicated or Intermittent Duplication

• | Vibration Duplicated - Difficult to Identify or Isolate Component

• | Vibration Duplicated - Difficult to Balance or Isolate Component

• | Vibration Duplicated - Appears to be a Design Inherent Condition

### Vibration NOT Duplicated or Intermittent Duplication

If you have not been able to duplicate the vibration concern or have only been able to duplicate the concern intermittently, review the following information.

Most vibration concerns that cannot be duplicated are due to either specific conditions that are not present during the duplicating attempts, or due to not following the procedures designed to duplicate concerns properly and in the sequence indicated.

#### Specific Conditions can Affect the Condition

Most attempts to duplicate a vibration concern are made after the vehicle has been driven to the dealership and perhaps even sat inside the building for a time. The opposite could also occur; perhaps the vehicle has sat out in the cold for a time and fails to reach full operating temperatures during attempts to duplicate the concern. The selection of roadways used to perform the vibration duplication procedures is likely to be in the near vicinity of the dealership. The vehicle is most likely empty of any payloads and usually not bearing any kind of trailer.

Caution: Do NOT attempt to duplicate a vibration concern with specific conditions indicated by the customer which would disobey local laws or ordinances, or which could cause damage to the vehicle or be dangerous and possibly cause physical injury or death, such as over-loading a vehicle, or driving at excessive vehicle speeds.

Important: If the information you gained from the customer indicates that one or more of the specific conditions listed applies to their concern, attempt to duplicate the vibration concern again, while carefully recreating the EXACT conditions necessary, with the exception of excessive speed, over-loading the vehicle or towing a trailer. You are responsible to make sure that the vehicle operates normally 'as-designed' and under 'normal operating conditions' ONLY.

Consider the following conditions which may not have been present while attempts were made to duplicate the vibration concern. Attempt to obtain more specific information from the customer as to the EXACT conditions that are present when they experience the vibration which they are concerned about, then attempt to duplicate the vibration concern again while recreating the EXACT conditions necessary, except those which pose a safety concern or are outside the boundaries of normal operating conditions.

#### Temperature, Ground-Out, Accessory Load

• | Flat Spots on Tires

| Tires which have sat and been cool for a time can develop flat spots.

• | Irregular Wear on Tire Treads

| Tires which have sat and been cool for a time will be stiffer and any irregular wear conditions will be more noticeable than they will be once the tires have warmed and softened.

• | Exhaust System 'Growth'

| Exhaust systems may exhibit a ground-out condition when cool which goes away once the system is fully warmed-up. The opposite may be true that the exhaust system is fine when cool but a ground-out condition occurs once the system reaches operating temperatures. [Exhaust systems can 'grow' by 2½ to 5 cm (1 to 2 in) when hot.]

• | Engine-Driven Accessory Noises

- | Belt Whipping

- | An engine accessory drive belt (or belts) could exhibit a whipping condition if the belt is deteriorating and deposits are building up on the underside of the belt.

- | Loose Mounting Brackets or Component Ground-Out

- | Engine-driven accessories such as a generator, a power steering pump or an air conditioning compressor could exhibit noise conditions due to either loose mounting brackets or due to related components of the system in a ground-out condition during certain operation of that accessory system.

- | Cold or Hot

- | These accessories could exhibit noise conditions when cool which go away once they are fully warmed-up, or the opposite may be true.

- | Load on an Accessory Component

- | These accessories could exhibit a noise condition while under a heavy load -- perhaps when combined with a cool or fully warmed-up condition.

- | Bent or Misaligned Pulley(s)

- | Bent or mis-aligned pulley(s) in one or more engine-driven accessory systems could contribute to a noise or vibration condition.

- | Fluid Level in Accessory System(s)

- | These accessories could exhibit a noise condition due to an abnormal amount of fluid contained in the system of which the accessory is a part.

• | An improper power steering fluid level could produce noises in the power steering system.

• | An improper air conditioning refrigerant level or an excessive amount of refrigerant oil could produce noises or possibly vibrations in the air conditioning system.

- | Incorrect Fluid Type in Accessory System(s)

- | These accessories could exhibit a noise condition due to the incorrect type of fluid contained in the system of which the accessory is a part.

#### Vehicle Payload

• | Heavy Payload

| The vehicle may have been empty during attempts to duplicate the vibration concern, while the customer may actually experience the vibration concern while the vehicle is carrying a large payload.

• | Trailer Towing

| The customer may experience the vibration concern only while towing a trailer.

#### Roadway Selection

The customer may only experience the vibration on a particular roadway. Perhaps the roadway is overly crowned or is very bumpy or rough.

### Vibration Duplicated - Difficult to Identify or Isolate Component

#### Aftermarket Add-On Accessories

Aftermarket accessories which have been added to the vehicle can actually transmit and magnify INHERENT component rotational frequencies, if the accessories were not installed correctly.

An accessory should be installed in such a way that it is isolated from becoming a possible transfer path into the rest of the vehicle. For example, if a set of running boards has been installed improperly and they are sensitive to a particular frequency of a rotating component, the running boards could begin to respond to the frequency and actually create a disturbance once the amplitude of the frequency reaches a high enough point (probably at a higher vehicle speed).

### Vibration Duplicated - Difficult to Balance or Isolate Component

If you have duplicated the vibration concern but have had difficulty in balancing a component or isolating a component, refer to the following information.

Most vibration concerns are corrected or eliminated through correcting excessive runout of a component, correcting balance of a component or isolating a component which has come into abnormal contact with another object/component.

Components which can generate a lot of energy and are experiencing excessive runout, imbalance or ground-out can produce a vibration with a strong enough amplitude that the vibration can transmit to components which are closely related. This type of a condition is usually related to and sensitive to torque-load. The most likely system that could exhibit this type of a condition is the driveline.

#### Driveline Torque-Load Conditions

An axle differential that has internal problems such as excessive runout of components, misalignment of components, imbalance, etc., can produce vibration concerns which may be transmitted into the propeller shafts. This sort of a vibration occurrence can increase or decrease in severity based primarily upon torque-load, but can also be affected by cold or hot conditions.

The propeller shaft and other related components may or may not pass inspections for wear or damage, runout, alignment, etc., depending upon whether there is only one vibration source or more than one.

#### Difficult to System Balance the Driveline

If after following the Vibration Analysis - Driveline Table you were instructed to system balance the driveline and you experienced difficulty in doing so while CAREFULLY following the procedures indicated (the EVA strobe readings seem to keep changing), then the axle differential to which the propeller shaft is attached should be suspected to have internal problems which are being transmitted to the propeller shaft. Refer to A Diagnostic Starting Point - Rear Drive Axle in Rear Drive Axle, for internal axle diagnostics.

### Vibration Duplicated - Appears to be a Design Inherent Condition

#### Check Service Bulletins

If BOTH of the following statements are TRUE, then check service bulletins for the condition identified. If the condition has already been identified and investigated prior to this vehicle, and has been determined to be something that is not truly design-inherent or that perhaps is not design-intent, there will likely be adjustments or corrections identified which will address the condition.

1. You CAREFULLY followed the steps indicated through reviewing the Diagnostic Starting Point - Vibration Diagnosis and completing the Vibration Analysis Tables identified and you have duplicated the vibration concern.
2. You have come to the conclusion through comparison with a very equally-equipped, same model year and type, KNOWN GOOD vehicle that the customer's concern is a condition inherent to the design of the vehicle.