First time some clown left turns in front of you and you hit the brakes and your truck and the trailer come to a complete stop in a straight line you'll thank the Good Lord above for your trailer brake controller. And that clown isn't just around on long trips or if you pull more than 6 to 8 times a year. Without a trailer brake controller and while the truck is trying to stop itself what do you think the trailer is doing? Cuz your truck isn't going to stop the trailer. PS-the tow haul switch has to do with shifting...stops gear hunting. You need to do some studying.