Ford Repair: ford explorer sport trac 2003 vibration/ shacking, ford explorer sport trac, ford explorer sport

Question
hello I have a 2003 ford explorer sport trac, it has been vibrating or bumping for some time now, it does not seem to make any noise, the steering wheel or foot pedals do not seem to shake It feels like the whole truck is shaking, it feels kinda like with every revolution of the tires it hits a bump. Well this is whats been done so far, i had it aligned put new tires on it, and that maid it a little better for a couple of months but now its bad so i noticed a leak from the rear differential seal  and so i replaced the wheel bearings and seals on the rear wheels and a seal on the pinion, one of the rotors was trashed and the caliper was stuck so i replaced both of them, this did not help any so i replaced the front bearings, still no luck, the drive shaft seems good it has no play at all i think thats it. Like i said it feels like bump bump bump bump at all speeds, the faster you go the worse it gets

Answer
i know you have had tires put on it but humor me-

find a smooth not very busy road-slowly take off and get to 15-20 mph see if you not only have a bump sensation but see if the truck seems to be rocking back and forth at that speed if so you have a bad tire/bent wheel or axle-if not follow up.