If your mechanicaly inclined and have the right tools, Ron's machine service sells oem AAM gears roughly 400usd that's with tax included. I recommend OEM gears. Not that chinese yukon crap like buying john deere parts made in china. If you plan on changing the carrier as well he sells Eaton trutrac with aam gears and install kit for like 900usd. If your running the 4 speed I recommend 4.10 gears. You have the 4l65e. Also if your truck didn't come with the heavy duty towing package I highly recommend a transmission cooler. If your going to 33s. Going 3.73 won't make a difference for the cost. Labor for a single axle cost 600 to 1500 depending on where you go. With that added weight of the grill gaurd and lift I highly recommend the gear swap to 4.10, especially if you tow. Also go to Oregon performance transmissions and buy there corvette servo for the 4l65e roughly 75$. It'll take you 1 to 2 hours to install just need a prybar snap ring plyers and and a large c clamp. Very easy install. It has more surface area and better apply pressure for 1-2 2-3 shifts. I installed on my wife's single cab 2010. Direct bolt on. If you change gears you will need to readjust your gearing in the computer so your traction controller works. So a tuner like diablo or a custom tune will do it or the dealership will do it for 150 with a tech 2.