2015Hd2500

Mine has almost 200k miles and wines. Has to be the pinion bearing. Base this on the experience and the pinion is the only thing spinning fast enough to wine and this is under a load. Axle bearing rpm is a lot slower and hardly ever fails. It is easy enough to check the pinion bearing for play. Block the wheels, put in neutral and with you hand grab the pinion flange and check for any slop up and down and in and out. Should be zero play. Then pull the plug and check the magnet. Should be clean. Even if you don't find anything will be the bearing. Find a good mechanic with references with warranty backed. You can verify the location or source using a magnetic pickup and stick it to the transfer case and measure the Hz and amplitude at speed on hwy. Then do the same on the rear end. The one with highest amplitude is your source. I use a guitar pick up and a 12vdc amplifier. Works the best.