Check the king bearings-I'm not sure on these trucks if it happens frequently, but on a big truck, bad king pin bearings will do that. Jack the front end up and grab the tire top and bottom; rock it back and forth and see how much give there is. Have a helper look and see if you have loose wheel bearings or if the knuckle itself rocks and forth. Again, not sure on these trucks, but it can be common on others to set a "preload" on the knuckle. This is done with shims and you use a fish scale to check essentially the amount of force it takes to move the knuckle right and left. I quickly looked through TM 9-8024, but will need to spend sometime and see if they show anything like this. Or maybe there is an overhaul manual that better covers this. Also check even tire pressures, and steering linkages-grab wheel on right and left when jacked up and rock back and forth and see if there is any play-again a helpers eyes are useful.