I had the same problem with my '80 and it was worn out axle pivot bushings. That truck is too new to have anything worn out, so it means something is about to fall off. Get it to a front end man before you kill yourself. If you want to try and locate the problem yourself, jack the truck up so that there is no pressure on the front wheels and grab each one and rock it up and down and back and forth while looking at all the suspension components. The problem should become apparent. If not, seek professional help! | 
