completely baffled, please help

Alright so on the truck in my Sig I've recently developed a nasty thunk in the floorboard I've replaced the shocks, track bar, all tie rods, and controll arm bushings, I've also tightens the hell out of each of the said items to no avail, also my balljoints are good I've been under the. Truck for countless hours with a pry bar and come along, and I can't seem.to replicated the issue, I though it could be the steering box but I feel nothing in my wheel, just under my feet, any advice on what to look at/for would be greatly appreciated this thing is driving me bonkers, also I should mention it feels very solid, not like a wire slapping the floorboard