Not sure about torquing the U-Bolts but if they have been tightened within spec, I would think you should be good there. I had the same issue with my '18 Sierra and after many trips to the dealer for multiple diagnostics, new U-Bolts, re-greasing everything, and new rear axels, it came down to stuffing some rubber into the leaf spring to stop the binding and the "popping". Been sound and pop free for about 50k miles now. Not positive thats your issue but it was certainly mine!