[Rred]

So 4H is an open diff, meaning that the front drive shaft is free spinning except when the traction controls kicks in and the rear driveshaft is always locked in to drive. And 4H/4L locked is the center diff is locked and fully engaged with equal power continuosly going to the front and rear drive shafts. ???

Also, what is the button just below the trailer button for? It's located just to the left of the onstar button and the bottom one of the stack of three.