Stop in for a cup of coffee

Yeah I stopped running the Cooper SSTs for that very reason on our farm trucks.
As far as I can tell, hub/bearings spins smooth and straight

Okay, I had that on my 89 Suburban. Had shop rebuild entire front axle with Yukon axles, limited slip diff. They set preload too tight and bearing on one side only lasted a couple years, should have done the work myself. Spring bushings all good, have you gone under the truck and watched a full lock to lock?