Strange humming noise

[HAULN-SS]

Hoping someone can help me diagnose a strange noise that started in the malibu yesterday. The best I can describe it, it sounds sort of like a truck with mud tires sounds going down the highway, just muffled.

It started randomly yesterday on the way home from work, and it seems to be tied to engine speed, but not one to one. In other words, if I am going down the road and accelerate, I hear the humming noise catch up to speed after the engine revs, not right as the engine revs.

Any ideas? :dunno:

[alteredspeed]

Sounds like it could be a front wheel bearing. When you drive it next go back and forth with the wheel like nascar guys warming up the tires at like 20 to 30 mph see if it gets noisier and quieter as you put more weight on a specific side. The side that is noisier on with pressure is the side that is bad. Just a hunch, Chevy's are known for there front wheel bearing issues.

[HAULN-SS]

thanks, will give it a try. Its not throwing any codes yet, and I am not good at diagnosing by noise

[alteredspeed]

It wont necessarily throw a code if the bearing is going bad. Some times they have to get really bad, because the only thing that will throw a code for that would be a wheel speed sensor that would show up as a ABS code.

[BLINGMW]

first figure out for sure if it's engine speed related or road speed related, that should be easy. Shift into 4th on the highway, don't change speed and see what it does.

Then find a big parking lot and make a left hand circle, then right hand, if it doesn't get any worse doing either one of those, then it's probably not a wheel bearing. Similar to what was suggested, but doing a whole circle usually gets more clear results.

If it does, now you know what side it's on at least.

Does it go away or stay the same with light brake application?

[HAULN-SS]

It is a steady noise at a steady speed. However, I dont hear it until about 30mph or so. And if, for example, I am slowing to a stop from 55mph at a red light, the engine revs seem to die down before the noise dies down. Can't hear anything at idle, but I havent tried revving it while staying still to see if I can hear it. Will try that next..good idea bout the parking lot.

[HAULN-SS]

So I have determined it is actually the wheel bearing. The question is - can I just buy a new hub assembly that already has a new bearing in it? I'm looking at this: <!-- m --><a class="postlink" href="http://www.autopartswarehouse.com/sku/Chevrolet/Malibu/Replacement/Wheel_Hub/2008/LT/4_Cyl_2-dot-4L/REPC283706.html?loc=Front&tlc=Brakes%2C+Suspension+%26+Steering&intcmpid=">http://www.autopartswarehouse.com/sku/Chevrolet/Malibu/Replacement/Wheel_Hub/2008/LT/4_Cyl_2-dot-4L/REPC283706.html?loc=Front&tlc=Brakes%2C+Suspension+%26+Steering&intcmpid=</a><!-- m -->

which is 112$, yet on that same site, the wheel bearing itself is 180$...am I missing somthing, do these hub assemblys not come with the the bearing installed?

[alteredspeed]

The one you have listed is the correct one and yes it is a hub bearing assembly. I have never seen any way to just replace the bearing. Not to bad of a job as long as you have a 36mm socket and a impact to get the CV shaft nut off, and some calm nerves.And make sure you torque the CV nut to the spec or you will be replacing the bearing again.

[HAULN-SS]

Did the wheel bearings today. Kind of a pain in the ass job. I ended up juts doing both of them. I wasnt quite sure which one was out, and figured if one was bad the other wasnt too far behind. 260$ for the parts..took about 3 or 4 hours, including the trip to Autozone. Not sure what the job would have cost if I had it done, but I guess I came out ahead by enough to make it worth it