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Annoying humming from back of car

In January I purchased a front wheel drive 2010 Toyota Highlander with 23,000 miles. When driving just over 60 mph, there is a fairly loud humming sound at the back of the car (seems to be more toward the right rear). The dealership replaced the LEFT rear wheel bearing (they said the right bearing was fine) and performed road force balancing on the new Yokohama Geolander tires I purchased with the car. Unfortunately, the annoying humming sound has not gone away. Please advise. Thanks!

Get to an area with no traffic and go about 40mph while slowly weaving the car back and forth between lanes. If the sound gets louder when you’re weaving to the left, and quieter/disappears when you’re weaving to the right, it’s most likely the right wheel bearing as you suspected.

+1 to @shadowfax A helper standing along the road listening as you drive by each way can add to your data. Noises like that can be tricky to pinpoint. I replaced a rear wheel bearing once only to have to repeat the other side when I realized I hadn’t affected the problem at all… Oops!

Many shops have a gadget with 4 or 5 microphones they can place around the car, and then get in with a headset and switch between the microphones to isolate where the sound is coming from while driving down the road. I wouldn’t be surprised though to see you having the other rear wheel bearing done. Might be worth it to switch the tires around too.

Wheel bearings should be replaced on both sides when one is done. A bearing may feel fine while on the rack but when the weight of the car is applied to it noise may surface.

It’s very strange that a wheel bearing on a Toyota with only 23k miles on it would be failing anyway unless there is a history behind it such as being underwater at some point.

If not the bearing there’s always the possibility of tire tread noise or to a lesser extent; an exhaust system hum.

These kind of sounds can be impossible to isolate. But I’ll add a few suggestions.

Wheel bearings are typically checked by attempting to wobble the wheel (checking for looseness) and spinning the wheel and listening. Sometimes, however, bearing roughness can be detected by turning the hub by hand with the wheel and tire off. The wheel and tire can act as a damper.

A second thought is that sound travels, and bearing rumbling that you’d swear was coming from one end/side of the car is actually coming from the other end/side. All four corners should be checked.

Four years is young for this, but it’s also true that sound moves through beaten-down spring bushings and upper strut/shock mounts (which contain dampers). It can also move through control arm bushings, sway bar bushings, etc. The car is too young for this to be other than a last resort possibility, but I thought I’d mention it anyway.

I can also tell you with a heavy heart and from personal experience that Toyotas of these past years have wheel bearings that do not stand up well to potholes. Toyota has gone to “tapered” ball bearings to reduce rolling friction, and any first year engineering student can tell you that ball bearings do not stand up as well to high load spikes, like you get when you hit a pothole.

George made an excellent suggestion too. Any good shop should have a system that utilizes piezoelectric linear accelerometers that produce “traces” that can be monitored and recorded on a simple laptop computer with the proper programming. Each spike, called an “event”, can be seen by the “event recorder”. By strategically placing multiple accelerometers, a good tech can isolate the area that the noise originates from, and even possibly the component.

If I think of anything else I’ll post. Hopefully one of these thoughts will help.

I’ll chime in

I believe the dealer mechanics made some mistakes

First of all, I’m betting they did NOT use the chassis ears to determine exactly which bearing is bad . . . left rear or right rear. It seems like they guessed wrong

Diagnosis beats guessing

Second of all, after determining which side was bad, they should have told the customer "After using our chassis ears and determining x side bearing is bad, we recommend replacing both rear bearings, because if x side is bad, the other one may not be far behind, as it’s been subjected to the same conditions.

For the record, those Chassis ears aren’t even that expensive. I believe the kit can be had for less than $200, so a shop and/or mechanic can’t claim it’s some expensive, high tech, exotic gadget

Find the jack access panel and see if the jack is loose. Throw a few big rags in there and see if the noise goes away. Some SUV’s are just noisy.

Thank you all for your great feedback! I have an appointment with the dealership next Wednesday and I plan to share with the service manager your suggestions. I’ll report back what they find. By the way, they had my car over two weeks, trying to figure out where the sound was coming from.

what was it? Wheel bearing?