Hello. I have a 2006 chevy silverado 2500hd 4x4 duramax. A little while ago I was driving when a loud grinding started coming from under the truck. At first I thought it was just the driveshaft support bearing do to the bushing be shot. After replacing the bearing I took it for a test drive and the grinding continued. As well as the transmission will no longer shift into reverse. From what I've seen the grinding is most likely coming from the transfer case but I've never heard of a bad transfer case causing no reverse. Should I look into rebuilding the transmission or should fixing the tcase fix the problem?