Have you ever had a problem vehicle with a vibration that just seemed to be impossible to fix? Have you performed repair work or installed parts, in an attempt to correct a vibration and it ended up being a complete waste of your time and the customer’s money? I have, and I know that I am not alone.
As you may already know, correcting a vibration concern has been much easier than diagnosing the source of a vibration. Correcting a vibration concern can be as easy as balancing a tire or as difficult as correcting a backlash variation problem on a ring and pinion gear set. You cannot correct a vibration concern without first diagnosing the source.
There have been many vibration diagnostic tools over the years, some mechanical and some electronic. Most of them are bulky and time consuming to setup. To make things worse, almost all of them are difficult to understand without hours of technical training because there were no definitive results. You had to decide what was wrong with the vehicle based upon the measurements displayed on the tools.
Today I suspect that almost all of you have a smartphone within an arm’s reach at this very minute. That smartphone (with its amazing internal sensors) along with a unique smartphone app, can turn your smartphone (and some tablets) into an easy-to-use-and-understand vibration diagnostic tool. The smartphone app I am referring to is called “NVH” on the Apple App Store, and “NVH for Android” on the Google Play store. Since both apps have slightly different names, we will just refer to them as “the App” in this article. By the way, NVH is an industry standard term for Noise, Vibration and Harshness. The App currently measures vibration and harshness; noise measurements may come in the future.
This is a very sophisticated professional diagnostic app. This App incorporates all of the vibration diagnostic experience, knowledge and expertise I have accumulated over the last 27 years teaching vibration correction at Weber State University.
The App can help you diagnose the source of a vibration on almost any car, light truck or commercial truck. It can automatically tell you the exact type of vibration the vehicle is experiencing (there are at least 10 different types of vibrations on a typical vehicle) and will lead you to find the exact cause of the vibration by following step-by-step diagnostic and repair procedures. I have identified at least 276 different causes of vibrations on a typical vehicle.
I have had many people laugh at me in disbelief when I tell them we have identified 276 causes of vibrations. I ask them “What are you going to do when the typical repairs (balancing the tires and driveshaft) have already been performed and the vibration is still there?” At that point you typically have a several options: 1. Search the internet for help; 2. Start replacing or swapping parts; 3. Admit defeat and send the customer to someone else; 4. Try to get some help. This App is an excellent source of professional help; it is as close to having me in the shop helping you as you are going to get (unless you are one of my current students).
Warning: Educational content!
Before discussing the automatic diagnostic capabilities of the App, we need to define three boring, but helpful-to-understand, technical terms:
Frequency: The number of times per second or number of times per minute a vibration is detected. The App uses Hertz (Hz) as the default unit of measure, but can be changed to cycles per minute (CPM) or RPM in the app settings. Any part on the vehicle that rotates can cause a vibration. Each of these parts has its own unique rotational speed. The App uses the vibration’s frequency to identify the type of vibration.
Amplitude: A measurement of how hard or harsh a vibration is. The unit of measure is g-force (the force of gravity). Low amplitude vibrations usually cannot be felt or heard, while high amplitude vibrations can be heard, felt or both depending on the frequency of the vibration. Decreasing the amplitude of a vibration is the primary objective of any vibration repair procedure. The App uses amplitude to identify the harshness of the vibration.
Order: The number of disturbances or shakes in one revolution of a rotating part. Each order of vibration can only be caused by certain failures. For example: Anything that is out of balance will only cause a first order vibration. In other words, balancing a tire with a second order vibration is a waste of time. Understanding this concept can be very helpful when diagnosing the source of a vibration. Each rotating part on the vehicle can have many different orders of vibrations. Obviously, there are many rotating parts. The App uses the order to identify the type of vibration and to guide you to the correct repair procedures contained in the help file.
Four easy diagnostic steps
Now that we understand the technical terms, let’s get back to the App. Using the App requires four easy steps.
Step 1: Identify your vehicle. First, the App needs to know some technical information about your vehicle. The App uses that information to determine which vibrations to pay attention to and which to ignore. For example, we would not want to confuse evenly spaced joints in the road with a tire speed-related vibration. Determining which vibrations to pay attention to on each vehicle is a complicated process. Depending on the vehicle, the app will use up to 31 different pieces of vehicle data while performing vibration analysis.
There are two ways to identify your vehicle:
- Pick your vehicle — The easiest method is to select “Pick Your Vehicle” from the main menu. The App will display a list of the top 28 vehicle manufacturers in North America. Just select your vehicle from the list, enter the tire size(s) and press “Start.” The App has a built-in database of more than 12,400 vehicle configurations and is updated each summer with newly released models.
- Unlisted vehicle — If your vehicle is not in the database, select “Unlisted Vehicle” from the main menu and supply your own vehicle information. This method works on any car or truck, including custom cars and hot rods. If you do not know your vehicle information, select “Find My Gear Ratios.” Once you have entered the vehicle information, press “Start” to continue.
Step 2: Go for a test drive.
LEGAL STUFF: Distracted driving is a safety concern for all of us. The preferred way to use the App is to get another person to drive the vehicle while you observe the App. If you cannot get another driver, no need to worry, the app will record the entire road test for you to review when you get back to the shop.
The App is now ready to record and analyze vehicle vibration data. If you purchased the optional Kiwi3 (for cars and light trucks) or Nexiq (for commercial trucks) Bluetooth datalink adapter (to read engine RPM instead of having the App calculate it), plug it into the data link connector (DLC) under the instrument panel. Notice, you must pair the Nexiq Bluetooth adapter to your smartphone before it will communicate with the App. The Kiwi3 does not need to be paired, it just directly connects.
Next, press “Start Recording” and set, or mount, your smartphone on something solid in your vehicle like the dashboard, a window or a cup holder in the center console, and go drive the vehicle. The orientation of the smartphone does not matter because the internal three-axis sensors will detect vibrations in any orientation. While performing the test drive, bring the vehicle up to the speed where the vibration is the most noticeable and then hold a steady speed for a few minutes while the App gathers data. It is very important to hold a steady speed while the vibration is occurring.
If you are able to get another person to drive the vehicle, there are three screens you can observe while on the road test.
- Vehicle View – This screen shows you an outline of the vehicle powertrain as you drive. Any parts with vibrations detected will glow red as you drive. Obviously, this will give you an indication of which parts are causing trouble. There are three different groups of rotating parts: 1. Tire-speed-related parts. 2. Driveshaft-speed-related parts, and 3. Engine-speed-related parts.
Step 3: View the automatic road test results. When you are satisfied that you have duplicated the vibration concern with the App recording, return to your shop, park the vehicle and press “Stop Recording.” The App will take anywhere from a few seconds to a few minutes (longer recordings take more time) to analyze the data recorded on your road test. When the analysis is complete, the App will automatically display the “Diagnostic Results” identifying the primary type of vibration detected. The primary vibration is the one that had the highest average amplitude (Harshness) over the entire length of the road test.
If you want to see even more details of the analysis, select the “Totals” button and the App will show you the number of times each type of vibration was detected on your road test. This is sort of like an engine misfire counter, except these counts are for vibrations detected. In the example below, you can see that the first order Tire-Speed-Related Vibration was detected 226 times during the duration of the recording.
If you want to see even more details, select any one of the types of detected vibrations to see the number of counts broken down by vehicle speed in 5 mph increments. In the example above, you can see the first order Tire-Speed-Related Vibration was detected 146 times from 65 mph to 69 mph.
Step 4: Follow the diagnostic procedures. As we discussed at the start of this article, you cannot correct a vibration concern without first diagnosing the source. In the previous step, the App identified the type of vibration the vehicle was experiencing, so you are now a lot closer to finding the source of the vibration. Equally important, you also know what types of vibrations the vehicle is NOT experiencing; every other type of vibration on the vehicle has now been eliminated.
What you may not know is that each type of vibration is only caused by specific malfunctions or adjustments that are out of specification. The App contains detailed diagnostic and repair procedures and information for all 276 possible causes of vibrations I mentioned earlier.
Vibration type example: As you may know, the most common type of vibration on any vehicle is a first order tire speed related vibration (T1). This type of vibration causes one shake per revolution of the tire. There are at least 9 other types of vibrations on a typical vehicle.
Vibration cause example: Think of the number of items that rotate at the same speed as the tire. We have identified 77 items or conditions that can cause a first order tire speed related vibration. An out-of-balance tire is only one of the 77 possible causes.
To access the diagnostic procedures for the type of vibration identified by the App, select “How do I fix this Vibration?” at the bottom of the Analysis screen.
The App will open a specific help file with a list of step-by-step diagnostic procedures for the type of vibration identified by the App. This list of procedures is arranged in order from the most likely cause to the least likely cause. The help file also includes hundreds of photographs of diagnostic procedures as well as detailed videos of common diagnostic procedures.
From this point forward, you just follow the step-by-step diagnostic procedures outlined in the App until you find anything that is out of specification or found to be defective. Make the appropriate repair and repeat the road test procedure with the App again. This is a process of elimination, but it is based upon proven diagnostic procedures I have successfully used and fine-tuned for many years. This App is the next generation NVH diagnostic tool, and now you can always have it within an arm’s reach at a moment’s notice. Best wishes!
