Inspection and Verification (Start Testing Here)

Noise, Vibration And Harshness (NVH) is becoming more important as vehicles become more sensitive to vibrations. This section is designed to give a working knowledge of the process of diagnosing NVH situations. It is divided into several sections based on the description of the condition. If the condition occurs at high speed for instance, the most likely place to start is under High Speed Shake. The Road Test will tell how to sort out the conditions into categories and how to tell a vibration from a shake. It will give a few hints on quick checks to ensure that a cause is either pinpointed or eliminated.

Become familiar with the terms. Use the Glossary of Terms to find the descriptive name of conditions not encountered before. After naming it, proceed to Identifying the Condition and locate the proper diagnosis section. Remember, by beginning at that point, most other systems in the vehicle have been eliminated. When the proper section is identified, the job is partly done. Always follow each step exactly, and make notes along the way to recall important findings later.

Customer Interview
The Noise, Vibration and Harshness Road Test starts with the customer interview. The service writer must get as much information as possible about the problem and, if possible, take a test drive with the customer, to minimize confusion arising from descriptive language differences. The history of the problem must be investigated: When was it first noticed? Did it appear suddenly or gradually? Did any abnormal occurrence coincide with or precede its appearance (such as pothole or curb impacts, minor collisions, etc.) Were any service procedures performed or parts replaced? It is also necessary to know any special conditions affecting the appearance and degree of the problem, such as road speed, type of road, drive mode, engine temperature, ambient temperature, etc.

A gradual appearance of the problem indicates a deterioration of a component, such as tires, front wheel driveshaft and joints, drive belts, or front wheel bearings.

A sudden appearance of the problem could indicate a lost wheel balance weight, or frozen front wheel driveshaft joint.

Identifying the Condition
If noise is produced as part of a vibration condition, correcting the vibration will eliminate the noise. If the noise is related to a specific component or system, refer to the appropriate service procedure for further diagnosis.

If a vibration exists check the following to identify the concern:

- Engine or Accessory Vibration, all speeds - Refer to Drive Belt Check Pinpoint Test H and Tip-in Moan Pinpoint Test B.

- High-speed shake, 80 kph (50 mph and up):
a. Refer to Steering and Suspension.
b. Refer to Refer to Transmission and Drivetrain/Drive Axles, Bearings and Joints/Wheel Hub or Brakes and Traction Control for front disc brake rotor and brake drum runout checks.

- Tip-in Moan - Refer to Tip-in Moan Pinpoint Test B. If the symptom still exists, refer to the Drive Belt Check Pinpoint Test H.

- Brake Shudder - Refer to Brakes and Traction Control.

Harshness is the term commonly used to describe the ride quality of the vehicle. A hard ride or harshness is usually caused by the tires or suspension system, namely:
- Overinflated, wrong size or wrong type tire installed on the vehicle.
- Suspension not sufficiently lubricated.
- Worn suspension components.
- Suspension components installed with preload on pivot point, bearings and bushings.
- Vehicles equipped with tires not specified by the manufacturer. (Different brand tires often give different ride qualities to the vehicle.)
- Bent or bound up shock absorber.
- Heavy-duty components installed on vehicle.

Noise Diagnostic Procedure
Read the following conditions before starting the Road Test.

Non-Axle Noise
There are a few conditions that can sound just like axle noise and have to be considered while performing road test diagnosis. The five most common are transaxle, exhaust, tires, roof racks and trim mouldings noise.

Therefore, ensure that none of these conditions are the cause of the noise before proceeding with an axle teardown and diagnosis.

Noise Conditions
Noise can be produced by many sources. The most common of these are the air intake system, powertrain, engine mounts, exhaust system, trim moulding and accessory drives.

To determine the cause of the noise, perform the Road Test and Road Test Quick Check Tests 1 and 4. Road Test

Then proceed to the Symptom Chart and perform the recommended test.

Vibration Conditions
Vibration can be produced by many sources. The most common of these are the suspension, front wheel driveshaft and joint, tires/wheels, front wheel drive shaft joint boots, front disc brake rotors, engine, transaxle, engine mounts, exhaust system and accessory drives.

To determine the cause of the vibration, perform the Road Test and Road Test Quick Checks. Road Test

Then proceed to the Symptom Chart and perform the recommended test.