I have a unusual whining humming noise coming from my engine. It's quite challenging to describe and has been equally frustrating to diagnose. The noise only occurs while the vehicle is in gear and driving. At least I haven't been able to replicate it in Park or neutral. The noise is however dependent on RPM. Being the most prominent in the $1,600 to 2200 range and very obvious when coasting in that RPM range. It will also show up when you let off the gas around the 3500 RPM range. When the noise is most obvious, it will also amplify by gently tapping the gas and letting off again. All u-joints have been replaced and the differential was serviced. The transmission and torque converter were recently replaced, which led to no change in the sound. The sound must definitely be coming from the engine or accessories in some way, but again only occur while the vehicle is in gear and moving. It's sort of a humming buzz and it's quite loud. I run a 4-in exhaust with a MagnaFlow. Joe, I can hear it clearly over that. For reference, the complete AC and cooling system with all accessory, pulleys and tensioner and belt were replaced within about a year and a half. I'm really quite baffled by this one. Anyone have any ideas. Also, I've searched all kinds of threads and forums and don't know that I can quite find the same issue.

 

Check your power steering fluid level. In my truck, the fluid level in the steering pump was very low, but the steering was still normal. My truck was making some weird noises like you described. I topped it off, and haven't heard the noise since.