I have a problem with my Explorer and it only seems to occur in the 35-40mph range. I keep trying to duplicate the noise with not much luck. I guess you could say it sounds like a grinding noise but I like to describe it as someone trying to release flem from their throat. Last time I heard it I was going 38mph and the RPM's were barely over 1k and I was maintaining that speed with foot barely on the gas peddle. As soon as I release my foot from the gas the sound goes away. If I'm accelerating at a normal acceleration I never hear this. It only happens when I'm cruising and happen to be at the 35-40mph speed with my foot barely on the gas. Anyone have any idea what could be wrong? No sensors have come on since I've noticed the sound.