Was going through the Cascades in Washington State today, there was snow. Put the truck 4H and noticed a strange noise any time I even slightly lifted off the accelerator. Essentially unless I was applying power there was a slight high pitched whirring/whining noise. There seemed to be a high frequency vibration to it. But when I went back to 2H the noise/vibration stopped. Put it back in 4H noise was back. Truck currently has 7,500 miles on it, I purchased it in July. I had a 2011 F250 and it never made a noise like this in 4H. It’s not the type of whine you hear in 4L on every truck out there. It has a harmonic to it that I’ve not previously experienced.