Weird Noise - 2002 Malibu

Hey, I have a 2002 Malibu and we have had the car about 3 years and since we purchased the car it has what a humming noise from the front when changing lanes on the highway or when making curves on the highway only when turning left.

Being an avid Car Talk listener, I decided this was probably being caused by wheel bearings and I decided to tackle the job myself and changed both left and right front wheel hubs and the noise did not change, it is still there exactly as before ! I also replaced the brake pads and rotors while it was apart.

Remembering other car talk converstions, I decided next that it must be the tires, I replaced the tires which were due for replacement anyway and guess what ? The noise is still there exactly as before !

Out of ideas, I took it to a machanic and he said that he ran the car on the lift and was able to reproduce the noise on the lift and he felt it was coming from the differential within the transmission. While it was at the shop I had him do a wheel alignment as well to eliminate any sort of suspension issue.

My question, does this make any sense ? To me when the car is on the lift, the differentil really isn’t doing anything, the wheels aren’t turning at different speeds because they arent touching anything therefore to me, the diagnosis of differential doesn’t hold water.

Any Comments / Ideas ?

When on a lift, the tires rarely spin at the same speed. The slightest difference in friction from one side to the other will cause one wheel to spin faster than the other.

What kind of bearings did you use? It is possible for the noise to still be wheel bearings if you cheaped out in that area (which is tempting as they are rather expensive). I have found that, when it comes to wheel bearings, you truly do get what you pay for, and the cheap ones can be bad out of the box. If you’re lucky, they will last you a year before becoming loose or noisy. The only ones I will install are National or Timken. Everything else is cheap junk. The reason I suggest this is because wheel bearings are a common trouble area on these cars as they age. To check this yourself, chock the rear wheels, jack up the car, put the transmission in neutral, and spin the wheels by hand as hard as you can while listening to the sound made at that hub. Any growling or roughness when you spin that wheel indicates a wheel bearing problem. Differential gears are a possibility also, but not as strong a possibility as wheel bearings. As for the mechanic’s assessment and whether or not it holds water, it does. The bearings in the differential are turning any time the wheels are turning. You may be thinking of the job done by the spider gears, which allow the wheels to turn at different speeds without binding anything up. I just still think a wheel bearing problem is more plausible than a differential bearing problem unless the transmission has been chronically run low on fluid, starving the differential bearings of lubricant.

Used I believe Duralast hubs on both sides.

I would tend to agree that there could be a defective hub but, I guess I would expect to hear some difference in the sound, it hasn’t changed at all, the sound and speeds where I hear the noise is exactly the same.

I have spun the wheels dont hear or feel anything.

The problem with the Malibu is there is no tranny dipstick, I cant check the fluid.