About a month or so ago, my 2000 Taurus began to make a grinding noise at speed. It started when I would let off the gas at about 45 mph, but now it does it at about 25 mph. I can't hear it if I give it any gas at all, but I don't know if it's just masking or if it goes away. The car has about 125k miles on it, up to date on everything right now but alignment. Had trouble with a coolant hose, IAC sensor, and a vacuum tube, but all of those are resolved. I believe the grinding is coming from the front, but having a tough time pinning down the exact location. Can anyone point me in the right direction of what to look for, or at least an idea so I can get it looked at? I have a trustworthy mechanic, but he can't pin down the location.