When I depress the accelerator from slower speeds, I hear a constant high-pitched whine from the front left. It will disappear if I lay off of the accelerator, and won't return depressing the accelerator again. Basically, accelerate - whine appears. Lay off accelerator- whine disappears. Depress accelerator gently- whine stays gone. Depress accelerator kind of hard again- whine returns. I though at first it was at higher gears but it comes when I put it in first and accelerated. Wheel hub was replaced three years ago. Any ideas? 2009 OR, 178k.