It was common with Military vehicles and some civilian ones (Mopar was always ahead of the game, engineering wise), to have the left side (I hesitate to say driver's side since many were built with right hand drive for the Brits) lug nuts with left hand threads. The theory as above, the spinning wheel will tend to keep them tight. All WM series Power Wagons have that feature, as do all WW2 Jeeps and post war jeeps up to about 1970 (which were not Chrysler). Funny thing; tank road wheels have all right hand thread, and they were all designed by Chrysler, and built there until the tank plant was sold to GD.