Whinning noise comming from the rear at higher speeds

[frohara]

Whining noise comming from the rear at higher speeds

I have a whining noise coming from the rear of my 2010 Mazda 3s (75,000 miles) that seems to be getting worse. It is louder the faster the car is going. I suspect it is the rear wheel bearings. Can I replace just the bearings, or do I have to replace the entire hub? Should I replace both rear hubs at the same time as I can't tell if it is one or the other? Is there a way to check the bearings to determine which wheel it is? Is it foolish of me to take it on a long road trip with this happening? Could it be something other than the rear bearings?

Apologies for all the random questions, and thanks in advance for your input!

 

[JiinXC]

From your description I would probably guess wheel bearings as well. If the noise is just starting you can probably keep driving on it for a little while, but I would get it repaired sooner than later. My old accord needed both rear wheel bearings replaced and it was so bad the brake rotors were fused to the bearing.

The way I know to check the wheel bearings is to see if there is any play in the wheel. It will be easier if the car is jacked up, but you can take the wheel in your hand and see if you can move it left/right and up/down. If there is a lot of play that is probably the cause of the noise and would indicate the wheel bearing is defective. Here is an example: https://www.youtube.com/watch?v=Nq1zGxnF8Qk. You can see what he does around the 15 second mark. Disclaimer: I would not suggest putting your hand under the wheel like he did while the car is in the air in case the jack fails and the car suddenly drops.

 

[BrianM3GS]

I suspect it is the rear wheel bearings. Can I replace just the bearings, or do I have to replace the entire hub?

Just do a Google search for "2010 mazda 3 rear wheel bearing replacement", and you'll see photos of a hub assembly (plus links to various discussions of replacing them). At $156 each, the extra cost of the whole hub (compared to just a bearing) is probably justified by the labour saving compared to pressing out and in just bearings, or disassembling and reassembling traditional bearings... so if the whole hub has to be replaced, that's okay with me. This design has been common practice for decades.

It looks like the second-generation Mazda3 rear wheel bearing assembly is the same design (perhaps the same part?) as the first generation, which is shown in this blog: Mazda 3 Rear Wheel Bearing/Hub Replacement. Looks straightforward.

 

[concept]

A common symptom of a worn wheel bearing is an increase in noise when the car is rounding either a left or right corner. The bearing noise will be more obvious during one or the other turns. The best way to verify is getting the wheel/tire combo in the air and rocking the tire with your 2 hands at 180 degrees apart while grabbing its outer periphery.

My MX5's front bearing was recently replaced as the whole hub unit. Total cost was about $300, I believe (parts and labor).

 

[MrCX9]

Had to do the drivers side rear wheel bearing hub in my 09 CX9. The sound got louder after a month or so, I was waiting for parts. Problem is I got all the way down to the hub and there are 4 Torx bit bolts on the back side that hold the hub in. These were not coming out as I couldn't get leverage or the straight shot needed with the car only jacked off the ground. The ABS tone gear is absolutely in the way. Normally I take these jobs on but this was one for the shop. Lots of expensive labor and a stabilizer bar. I ended up out $400 bills. After I already bought the bearing.