On a recent road trip, started hearing an occasional moaning sound. Seems to happen when I accelerate pretty hard after braking. Say, if someone in front of me is turning, then I'm getting back up to speed. The noise sounds like a quick short moan, as if there was some metal rubbing. Doesn't seem to be coming from the motor, more like the under carriage area. It seems to only happen in the lower gears when I really push the throttle hard. It's a short noise that lasts for a second then stops. Truck has 19,500 miles on it and has been babied on our slow roads in the Florida keys.