I have a 1998 Fleetwood Bounder with a P30 chassis. When on the interstate, and tractor trailers go by, it feels like it pulls the RV into the truck and with this sway, it almost feels like the RV is ...
That's called "laminar flow". The air being displaced by both the truck and your rig speeds up as it passes between the two and creates a low pressure. Your rig being the lighter of the two gets sucked into it. There's not much you can do about it, except keep a tight grip on wheel, sometimes you can lessen the effect by turning away from the truck. If the bushing and ball joints on you rig are worn, the more the effect.