65 Suburban Posi Noise When Hot - Additive Didn't Help

[RoyL]

Sorry, this seems to have discussed in several places, didn't want to tag onto an old thread, but bring what I read to my situation and see what I can learn.

Had the Burb since January. Got her running and have been taking short trips checking things out. Didn't notice the noise until after a longer trip. After reading several similar threads here and elsewhere, my posi noise sounded typical, "clunking" when turning from a stop or turning at very slow speeds. The clunking is pretty severe, feels like the rear end is gonna fall out. I tried the most recommended solution: Add the posi additive and the noise will go away. So I drained the diff, added the gear oil (80w-90) and the posi additive (generic at OReilly's). I saw no metal shavings in the diff oil when I drained. Thought that worked but once it got up to temp, the noise was back. Tried circling around in a parking lot left and right turns to "work the lube in?" No help.

What do I try next, before taking to a rear end shop? Axle bearings?

Thx,
Roy