Here’s something we as technicians see a whole bunch of….bad hub bearings. Whether they are causing the Antilock Brake (ABS) light to come on, or are just making a terrible grinding or growling noise as you drive, these are replaced almost daily at our shop on just about every model of vehicle. Today I had a regularly seen vehicle in the shop, a Chevrolet Equinox. The customer was complaining about both the ABS light being on, and a noisy condition while driving.
After a quick test drive, I heard the usual ‘growl’ type noise from the front end which is almost always a bad hub bearing assembly. Sometimes very worn tires can make this same type of noise, but it is usually discernable between the two with some experience. Along with the ABS light being on, I felt pretty sure just one of the bearings was at fault.
Getting the Equinox racked up so I lift it in the air is a great help since you can have the drive wheels turning and then get under and give a good listen to each hub. I found it was the left front that was making the noise. I also scanned the ABS system to check for trouble codes and found a code stored for the left front wheel speed sensor, a C0035. Now, with little other diagnosis, it was basically confirmed that the customer needed a new left front hub bearing assembly.
For those of you who don’t quite understand much about these hubs, let me explain a little. The hub bearing handles the load of the vehicle between the suspension knuckle and the actual wheel that is bolted to it. The ‘bearings’ inside it are not serviceable as it is a sealed unit. Also, the wheel speed sensor for the antilock brake system is an integral part of the hub assembly as well. There are windings and/or a reluctor ring inside that transmit the signal to the system.
When one or more wheels are transmitting a different signal than the others, or if one or more wheels has no signal at all, that’s when you will set the ABS light on and trouble codes will be stored. More often than not, it’s the hub assembly that has gone bad, but there are instances where the wiring is to blame outside the hub area and up into the actual ABS harness. Rubbed through areas, or ‘chaffing’ as it’s called can wreak havoc on a wheel speed signal, as well as moisture and corrosion. All of this should be checked out when diagnosing this type of problem.
As for this Equinox, it was indeed the hub that was bad, with internal failures causing the bearing noise and setting the wheel speed sensor codes. Replacement requires removal of the brake caliper and rotor, the axle nut, retaining hardware for the hub itself, and disconnection of the ABS harness connector. Pretty straight forward stuff, but this body style is known for excessive corrosion between the suspension knuckle and hub. Being different metals, steel and aluminum, they corrode excessively and basically become welded together. Removal often times requires the use of large hammers, air tools, prybars, and a lot of patience. I’ve even personally had a hub that was so badly stuck to the knuckle, that a press was needed to separate the two, and even ended up snapping the knuckle in two!
Luckily this particular hub came off pretty easily compared to others, and was a fast repair. Down the road they went, happy with a properly functioning ABS system and without the terrible noise they had before. Another satisfied customer!