Hi, I have a 1985 cucv blazer with the NP208. The truck drives quietly for about the first 10min of driving. After that a grinding/rattling noise seems to come from the transfer case. I replaced all the universals and just rebuilt the rearend. The noise gets louder in reverse and especially at highway speeds. I am thinking it could be the chain. If anyone has any idea what this is please post. I have a whole new bearing set and chain but would only replace the chain for now due to time constraints if that was most likely the problem. Thank you.