The definition and a video of sway has been posted. Lets discuss the mechanics of the push-pull. The front of semi tractors, large buses and motorhomes all push air off to the side when traveling down the highway. This air is commonly called a bow wave. Classic Petes, push more air than the aerodynamic Volvos. When the big vehicle approaches the rear of the trailer the bow wave pushes on the rear portion of the vehicle being passed, in this case a TT. Picture the passing vehicle in the left lane, the vehicle being passed is in the right lane. The rear of the trailer is pushed right, the pivot point is the axles and the front of the trailer goes left. This force on the ball to the left pushes the rear of the tow vehicle to the left requiring the driver to steer left to maintain a forward direction (sort of like driving in snow to correct a skid). Remember, the lever is a multi-thousand pound trailer. When the front of the passing vehicle gets to the forward section of the trailer the bow wave pushes the trailer and the rear of the tow vehicle to the right, while the rear of the trailer goes left, which necessitates the driver to correct to the right to keep going forward. With me so far? Good, now answer these questions for me. How exactly does the sway gimmick, with only a couple hundred pounds of resistance negate the leverage of a multi-thousand pound lever? Why, since my duelly is supposedly impervious to sway, is it not impervious to the push-pull?
So, set me straight. When driving a semi, you looked down at the hitch while passing a trailer and noted if it had some type of sway control gimmick device attached. The ones that had them did not push-pull or sway. The ones without would push-pull resulting in sway. Since we know what sway is, (the uncontrollable side to side motion of the trailer) how often did that happen? Every time? Once every five times? Once every 5-100 times? Once? I'm forecasting none of the above. Have you ever pulled your trailer without the sway gimmick installed to compare the push-pull affect, or is it the type that the WD and the sway apparatus are one? You see. I have pulled the same trailer with both types of hitches. Through a thunderstorm in Dallas, the desert wind of the southwest and about four thousand miles of freeway and 2 lane highways. Not one iota of difference, and I get passed by much faster semis and buses a lot since I tow at 57 mph.