Hello, I bought a 91 explorer from a friend of mine and one of the major problems it has is the 4 wheel drive. I didn't test it durring the test drive but he said that while you can shift into and use 4wd, it makes loud noises when you shift into and out of it. Does anyone know whether this is a problem with the switches or the transfer case? I dont have the truck yet to take pictures as he was nice enough to go get it inspected for me, but just in case anyone might have had this happen, any ideas to what might be going wrong? and if it is teh transfer case, how much would it cost to replace? Thanks.