Rearend gear ratios

You need to find the RPO sticker on the vehicle to determine which gear ratio you have. It's usually on the inside of the glove box door. It will be a large sticker that says do not remove. You'll see letters and numbers in groups of three on the sticker. Those are your option codes. Take a picture of it and visit your local Dodge Dealer. They can tell you what options you have and the gear ratio you have. The last eight characters of your VIN mean nothing. The 4 is the model year (2004), S is the assembly plant (Warren Truck Assembly), and the last six digits are simply the sequential unit number of your truck. Hope that helps! Jim