First rule of four-wheel drive. DO NOT engage 4WD on dry pavement unless you have a full-time system. When you put it in 4wd the front and rear driveshafts are turning the same number of revolutions. When you make a turn, the front and rear tires are not turning the same number of revolutions. Because everything is tied together mechanically something has to give to keep those driveshafts in synch. The difference in rotation is causing the binding, chirping, etc.. Your differentials may be open, but there is no differential action at the transfer case to allow for differences between front and rear. If you're lucky, traction is lost momentarily at the tires and the slip, spin, or whatever to ease the binding. If you're not lucky, something gives inside the transfer case and you get a big, fat repair bill. Leave your vehicle out of 4WD unless you are on dirt, snow, mud, or something which will allow some "give".