I have developed a knocking noise from the front driver’s side wheel area. Sounds a little like a brake that is seized on freeing itself. Happens when I engage reverse on a slight slope with my foot on the brake and also when the gearbox downshifts at lower speeds. I can’t reproduce the noise by accelerating hard and immediately lifting off (I thought it might be a driveshaft) and it is intermittent. Anybody have any ideas? 2013 SD4 Auto.