I think all the daks come with the tow/haul button wether it has the tow package or not. When you engage the button it disables 5th gear so you don't beat your trans when you have any kind of a load on or in your truck. The difference between 4th and 5th gear is only 400 rpm and your trans would do a lot of banging back and forth between the two if you don't disengage 5th w/ button. It won't take much weight to put a beating on those two gears.