HELP WITH MY TRUCK?!?!?!?!?

ohkay.. its a 1997 ford f150 5.4 triton v8. and when im going down the road going through gears, its fine but when its in low gear and i give it gas. it starts bouncing and jumping around. but when its in a high gear fixing to transfer into another gear its fine..what the freak is goin on with it?