So i have a 1986 F250 with a 460, pretty sure t-18 4 speed, and it has 4x4. Sometimes when i shift at lower speeds and the engine gets kinda lugged i hear a couple knocks. NOT from the engine, but from below my feet. sometimes i can even feel it through the floor. Anyone else have this happen? should i be worried? thanks a bunch

 

More than likely you have a motor mount or the transfer case crossmember/mount is loose. I would check that stuff. Take a pry bar and try to move the tranny/transfer case around. You may find it's just laying in there and the rubber mounts have broken loose.