My car is making a random metalic sound under the hood at about 3000 rpm under acceleration. If i puppy it and keep the rpm down i do not hear it. It sounds like a rotational dry bearing chatter, and it is brief, does it for an instant then stops. I do not feel it in the car, only hear it. engine does not miss a beat, no feeling through the shifter. Just noise. kinda loud too. Any ideas guys?