This is a 3/4 ton rear end with full-floating hubs, right? (axles can be removed from the center of the hub) Try pulling both hubs off and inspecting the inner and outer wheel bearings. It's beginning to sound like you've had a bearing roller come adrift and it's trying to lock up the hub occasionally. If that's the case, most of the metallic debris will be trapped in the hub with the bad bearing. Hub bearings can get VERY noisy and still keep rolling.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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