Recently had a junk yard transfer case put on my truck as I'm still in college as most of you know. Truck drove fine for a couple of days until I took it up to the mts (300 mile one way) to help my family do some upkeep work on our cabin. When I was getting ready to back down into the driveway, I shifted it into reverse and started to back up until I heard a slight bang and we came to a dead stop. After thinking I backed into a tree or pile of wood I moved forward and tried again. This time I could move in reverse but had a noticeable rattling sound. I was able to get the truck home but it acted up a couple of times at stop lights. Could this be the transfer case or the transmission like I am thinking?? All help would be appreciated!!