Anti-chucking pin box devices

stsmark wrote:
I always thought that airbags are kind of a twofer, leveling and cushioning. The pinbox does not know where the cushioning is coming from.

Yes it does, even with bags the truck will still transfer all of it's movement into the hitch and vice versa. The air pin box allows it to almost float on the truck and absorb movement from the truck and trailer.