Same info I found but some people in this thread are deadset as it being something broken, its literally a feature and works damn well too it just sounds awful. Other vehicles have similar software controlled "BLD" and they too make weird noise its just a side affect of dragging the brake. Now I will say that I wish you could turn it off when you don't want to have it on...Actually just found this in the manual, so apparently it is normal. In 4WD Low even though the ESC is turned off (or in 4WD High and OffRoad+ is on, which also turns off the ESC), the BLD will continue to operate "aggressively" - so the ABS isn't kicking in but instead this BLD system is kicking in when in 4LO first gear and/or wheels turned sharply....
Page 162 in manual -
"Traction Control: Aggressive brake lock differential tuning at slower speed or FIRST gear"
(not sure if that is supposed to say "turning" or if they meant "tuning"???)