Help with drivebelt.
Anyway, On to your question. It is easier to do this if you have a serpentine belt wrench. It looks like a fairly large flat bar with a socket on the end. If you don't have or can't get that then a breaker bar should work. You can use just a rachet but it is a pain.
There are 2 pullies. One pully is the idler and the other the tensioner. The lower one is the tensioner and has a left hand thread bolt on it. The other one has a torx head anyway, so you should be able to mix them up. So to loosen the belt put tension to the left or passenger side of the truck. Once the tension is removed slide the belt off the idler pulley then just release the tensioner. The remove the belt and reinstall new one in reverse order. Make sure you get it on the same way. There should be a sticker on the radiator support for the belt routing. If it isn't there make sure to remember how the belt was positioned.






