My problem turned out to be mismatched races and bearings. I used the races that came in the Diamond axles, but those could have been 20+ years old, as it appears Diamond uses used knuckle balls, not new ones. Anyway, once I installed the races that came with the bearings I was using, it worked OK.

Hunter, my FSM says the knuckle preload is around 8-13lbs. Are you sure you're not referring to the wheel bearing preload?

Anyway, I ended up using one thick shim that was on before, and none of the others from the kit, or the other thin ones that were on before. Mine's a little tight - around 14lbs - I figure they'll settle a little and I'd rather they be a little on the tight side, anyway.

Mark