At 45 miles an hours the jeeps shakes wildly why

Check for rocks stuck in tread , check for proper air pressure in tires, jack up each wheel/tire and spin it to see if tire or wheel is out of round (up and down motion) or wheel is bent (side to side motion) . Up and down could be either broken belt in the tire or a bent wheel either one. If it isn't a tire or wheel problem then you need to have a mechanic check steering linkage , ball joints, esp if they haven't been kept serviced regularly.