I don't really know either, but , I have a 4x4 myself, gmc 2500, maybe together we can see what it is. my gmc has a shift lever on the floor to change 2w, 4w, hi, lo range, n. I'm assuming so so you., is there a switch @ transfer case, that is @ fault ? hope that grinding stopped that you mentioned. seems to me the transfer case is where we should look at first. I'll get back to you