Have you inspected the rear-end gear oil?
I am kinda suspecting that it has some issues withthe side-gears and spider-gears in the differential.(just a possibility)
It would be a good idea to jack the truck up one end at a time. Put it on jack-stands to be safe.
Spin the rear tires and listen to the noises if any. (I had one truck that had cracked the differential side-gears and the axle-shaft splines would occaisionally slip inside the side-gear splines making a loud clunk noise).
shake, pull and wiggle each wheel to see what movement you get at each wheel.
Do the same with the front end. shake the wheel side-to-side, up and down and see what movement/noise you get there.
Also inspect all of the leafsprings really close for cracks or a broken leaf.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!