[Tom Roper]

And maybe this should go without saying, but to some people I've known, they put it in 4WD in the fall, and don't take out of 4WD until spring. It's a PART TIME system.

Clunking could be in the front diff, transfer case, driveshaft splines, u-joints. To the extent that you're able to crawl under it, you can grab hold onto parts like the driveshafts and turn them back and forth with your hands to check for freeplay, and locate clunks. You can also put the vehicle up of (4) jackstands, and run it in 4wd while someone listens for where the clunks/vibes are coming from. Could be as simple as low fluid in the transfer case or front differential, or a driveshaft u-joint.