Auto Service World
Feature   September 1, 2011   by By Tom Venetis, Editor

What is that noise?

Making the wheel hub assembly a part of the maintenance routine

Diagnosing wheel hub problems can be tricky. When problems happen there are often few visual clues and sometimes the noise a worn wheel hub makes can be mistaken for a problem occurring elsewhere in the ride control system of a car.
“This is a tough question due to the fact that the technician cannot see into the inner workings of the bearing, because it is hidden,” said Tom Fritsche, director of product development with Beck/Arnley. “There are few signs that a bearing could be going bad, such as noise or wheel wobble and pulsation.”
This is why it is important that the first step in diagnosing wheel hub problems, even before taking the car out for a test drive or throwing the car up onto a hoist, is to listen to what the vehicle owner has to say about the car, said Rick Domin, senior product analyst with Timken, a manufacturer or wheel hub technologies for the aftermarket.
What a service writer or technician can ask is when the vehicle owner drove the car was there a noticeable snapping, clicking or popping noise heard, or a grinding noise or even a humming or rumbling sound? A snapping or popping noise might be a sign of a damaged CV joint, but it could very well be excessive bearing end-play. The grinding noise may be a sign that the roller or raceway in the hub assembly has lost its integrity. The humming or rumbling noise might also be a sign of bearing failure, particularly if the driver says the noise increases when steering wheel is turned slightly to the left or the right. To help pinpoint where the noise may be coming from and be more certain that it is a worn hub assembly, there are several technologies available. One popular one is Chassis Ear, a system that uses six wireless mics with alligator clips so they can be attached anywhere in a vehicle’s compartment or ride control system while the vehicle is being driven.
That is all when and good, but what if there is no noise or one that a technician can with certainty distinguish as being a failed hub and bearing assembly?  Certainly, it is a challenge for even the most experienced of technicians. However, checking for wheel hub assembly and bearing problems can, in fact, be made part of a routine vehicle inspection or included as part of a check during other work on a vehicle such as ride control maintenance or brake replacement.
Steve Cartwright, chassis curriculum manager with Federal-Mogul Corp., makers of Moog hub assemblies, said once a technician has a car in the air “grab the tire at the 12-and-6 o’clock positions and move the assembly and feel for the ‘play’ in the bearing. If (the technician) has the tire and rotor off, it is also not a bad thing to grab the hub bearing by the studs that hold the wheel and feel for any noises or roughness when turning the assembly. Sometimes, if the vehicle is a front-wheel drive, if a bearing as a roughness in it or there is a ball that has some damage in the raceway, you will feel that in the rotation of the hub. You are feeling for roughness or looseness in the bearing.”
In many cases, a wheel hub assembly or bearing failure can be caused by road conditions, so it is important to ask the driver if problems and noises started after they hit a particularly bad patch of road or a deep pothole with a high amount of force.
“The number one issue we see with hub assemblies is contamination, water or dirt contamination,” added Timken’s Domin. “This sometimes happens when the hub assembly reaches operating temperatures and you suddenly immerse the hub assembly in water, say hitting a flooded pothole and then there is a rapid change in temperature. That change in temperature could cause (the hub assembly) to suck in some moisture or other contamination.”
Also, a technician should keep in mind that if some ‘play’ is found in the assembly, it does not automatically mean it must be replaced. While it is common to replace the assembly if ‘play’ is discovered, some makers of hub assemblies do allow for a small amount of ‘play’ to happen in the system. It is best to check the manufacturer’s specifications to see if this is the case and what range of ‘play’ allowed.
When it comes time to install a new hub assembly, Federal-Mogul’s Cartwright said it is critical to takes things slowly. Too many shops rush the repair, with some technicians bragging they can do a wheel hub assembly removal and replacement in fifteen minutes.
“That worries me because it suggests they are not cleaning the components,” he added. “The hub bearing has to fit into the knuckle freely. It is quite common, when you are doing a hub bearing replacement on a truck, like a Dodge 4-Wheel drive model, that there is a lot of rust accumulation around the hub bearing where it fits into the knuckle. Once you get the old one out, you just don’t cram a new one into all that rust. You want to clean out the hole in the knuckle to make sure the hub bearing fits freely into it.”
Cartwright also recommended that technicians avoid using an impact gun when removing the nut so as to avoid dropping rust into the area where the knuckle will fit into or damaging the internal components of the new hub assembly.
Also to keep in mind is to replace a worn hub assembly with a quality part.
“The most common cause of premature bearing/hub failure are manufacturers cutting corners, such as not using quality steel, not finishing the bearing surfaces properly, not using high-quality grease, not setting the pre-load properly, not using a high-quality sensor or improper heat treating,” Beck/Arnley’s Fritsche said. “You need to do your homework in your quality investigation.”