First of all, all stock (engine, exhaust, etc). I've noticed this for a little while..I only hear it when the radio's off. It's a quiet (from in the cab) hum type noise I hear while driving along. I listened a little better today....It starts at 1300 rpms, regardless of which gear I'm in. Usually I'm either just feathering the gas pedal, or just driving easy, maintaining speed (30-40) down the road. It sounds like the hum you get when you blow across an empty beer bottle. So, to try and rule out gears/transmission, I put it in park when I got back to my driveway, and gently got the rpms up to 1300.....still heard the hum, although maybe not as loud, not sure, but still heard it. Always at 1300-1400, and goes away around 1500+. Weird.....any thoughts?

 

water pump, power steering pump, idler pulley

 

Oh beautiful.

 

open the hood and rev the motor, if it's engine related at least your closer to the source, may help pinpoint it.

 

Yeah, I'll do that. Now, the noise doesn't sound so loud/bad from the cabin....is it normal noise? Or a part about to fail?

 

I would check your fluid levels on everything. If the power steering pump gets low it will start to wine. Make sure you fill the power steering with ATF-4 (NOT POWER STEERING FLUID). If the power steering is low, make sure to check the lines for leaks. Also check under the rack and pinion boots for leaking fluid from the seals.

 

i have no hum from mine. it could be anything really, like superdak says, anything that is spinning could be the sourse, you have to narrow it down.