Thanks for replies. First, never said lifted. New springs just put truck back to normal height. Tried looking at all bushings, did replace rear upper control arms a few years ago and saw what a bushing that appears normal looks like after removal and seeing it's cracked, dry rotted. Hence the quotes around "appear". Great suggestions and will take the next day or two to see what else I can see. Originally before replacing springs and shocks, was definitely hitting the bump stops above the axles and that may have been a slightly different sound (or maybe that doesn't make a sound at all) than now because there is no way I am hitting them now. But it sounds the same and possibly the sound I heard before was the same issue that was caused by worn suspension parts?

It's a ca-clunk when going any speed and no noticeable affect on driving. Can feel it. It feels like the rear axle is slamming the underside of the truck IN THE BACK. Definitely not a soft, springy feel over medium bumps. Small bumps feel fine, just those little larger ones that you hear and feel it.