Hey guys about a year or so ago I noticed my truck started getting a weird vibration right around 70mph but only under a load, it seems to do it when accelerating somewhat hard but it comes and goes fast until you hit 70mph, then it will stay till about 78 or so. Its only under a load and the more the load the louder/worse the vibration is so far I've had my trans and transfer case rebuilt, new tires and alignment, changed all the fluids and changed the u-joints and even tried a whole nother drive shaft as well as removing the from and it still does it!!! anyone have any ideas??