While driving my 2006 Ford F-150, when I press the gas and the RPM's go above 2, I begin hearing a Scratchy noise (Almost like a wheel bearing is broken) coming from the front driver wheel well area. However, I've had a broken bearing in the past on a previous car and that noise was constant. This noise only happens when the RPM's hit 2 or higher, and i'm accelerating. When I release the Accelerator, the noise stops.. Any ideas what this may be?