in my extensive towing expirence anything with a shorter wheelbase will cause a trailer to "fishtail" the heavier the load the worse the sway, also if the loaded traier is significantly undersized for the vehicle then it will sway too. so the 3/4 ton was too big and the s10 was too small, think of Goldylocks here people the correct vehicle for the load is key, for example never use a 1989 Full size Ford Bronco to haul a 16 foot flat bed trailer with a skidloader and 3 tons of pea rocks!!!