Ram used to put that info on a sticker inside the glove box, but not any more. Most trucks will have the 3:55 as that's the standard ratio. A couple things you might think about on a 12 or 13, is although the two years are almost identical they are worlds apart. Almost every bit of electrical, the frame, the trans(mid year got the 8 speed), the steering(electric now), and many other things were changed for the 13 model year. Get a 13 if you can afford it. In my own experience, it almost pays to buy a new truck, as the prices I found made them close enough I bought new. Good luck