2000 Venture Engine started a rumble (sound) during idle
2000 Venture with 240K miles on original drive train. The engine started a rumble noise in the front of the motor around the serpentine belt at low idle when the motor is placed in drive (load). In neutral, the noise never appears. Speeding up the engine off idle at load, the sound goes away. The engine idles and runs smoothly during all of this. It almost sounds like a bearing on one of the pulleys going bad. Suggestions?