Hill descent control

[Frank8]

You answered one of my questions. I thought you might be engaging HDC at too high of a speed (max is 50mph for engaging it) but that's clearly not it. Does it make sounds if you come to a full stop and then engage HDC?
Does it happen under any other braking situations in normal driving?

No, regular braking is fine at all speeds.
HDC becomes inoperative at 31 mph according to manual. If I have it on at 35 and slow to 30 I can feel it start. No growling. Down at 10 or 15 or so, if I slow even more then it growls. Not as bad as before.