rear wheels off the ground/in neutral either bearhugging a wheel & rotating it forward and backward how much play are you estimating you are feeling/hearing in the rear end? further up .006-.010" was posted as a normal "backlash" dimention or just grab the pinion yoke by hand & rotate it back & forth. Up front I ain't a tranny guy but I would do the same thing & others will advise further & didn't we cover checking the ext housing bushing wear? I ain't thinking the ujoint(s) are causing the clunking but if one or both of em are binding/not moving smoothly they will wear out fast (you said they were a bit tight but no looseness correct?) & then clunk. this might be a combo of the R&P backlash and something going on in the trans but from prior I'm leaning (barely) toward the trans. post that video with good sound & keep the ex noise out of it as much as you can.