This is driving me crazy. I have a 01 Limited 4runner 4WD with 149700 miles. This noise has been there for a long time. It is very low. If you have the radio on you can barely hear it. Whenever I accelerate from a stop I hear a very slight constant noise. It’s hard to explain the sound. Not really a metal on metal more like a noise caused by rotation. It speeds up and gets a little louder if I press the gas harder. Once the vehicle is at a constant speed it stops. I only hear during acceleration. I don’t hear it at highway speeds probably because of the road noise drowning it out. It sounds as if it is under the car around the passenger seat or under the middle console. If I roll down the window the wind drowns it out. I cannot pinpoint this. My first guess would be the drive shaft joints. But I have no idea. It does not happen while revving the engine. Thanks for any help.