I have a 2015 2500 with duramax. 140,000 miles. 4x4. Have had no issues with driveline and don't use it for heavy hauling. A few weeks ago it started giving me a metallic clunking sound when I would take off pretty quickly from a stand still. Like win the race from one stop light to the next kinda thing. Now sometimes it will give me two pops. Will also do it if I take off hard in reverse. I put it in 4 wheel drive and it doesn't do it. I pulled the rear drive shaft to check the splines coming out of the transfer case and all looked new. The u-joints seemed to be fine. It is a one piece shaft so that is the only slip joint. Any thoughts would be much appreciated.