whining noise...

At first I thought it was coming from the front of the car, maybe my alternator. It's a faint whining noise that becomes louder the faster I go. Then I sat in the back the other day while my sister drove home and it was much louder from the rear of the car. So what the heck is it? Sort of a whistling/whining sound as if a gear is getting old. My friend said UH OH, YOUR REAR. But I'd like you guys' opinions. What do you think it is?

Put the car up on hack stands (rear) and start the car and put it in gear, give it some gas and see if the noise is in the rear...go back under there when someone has it in gear giving it some gas and see if you can pinpoint the noise. Next, pull the differential pan and have a look. If it looks OK, put the pan back on (with new gasket) and fill 'er up with synthetic gear lube. take it out for a drive and see if it is still there.

You only hear it when the car is moving?

Yes, it's only when the car is moving that I can hear it. It is definitely coming from the back though, and it doesn't sound like the fuel pump. I know (unfortunately) what they sound like when on their last dying breath lol.

Do you have stock gears?

Do you have stock gears?

:1:

Larger gears can be talketive. could be improper backlash setting if they were replaced, but that would create a noticable clunk when you get on it.

it could also be the rear wheel bearings, or we're certain that the gears are the problem?