1. Check the Vehicle Identification Number (VIN): The VIN contains coded information about your truck's specifications, including the axle ratio. You can decode the VIN using online resources or a VIN decoder. This is the most reliable method.
2. Look at the axle tag: The rear axle housing usually has a tag riveted to it. This tag will specify the axle ratio (e.g., 3.55, 3.92, 4.10). You'll likely need to get under the truck to see this. The tag might also list the manufacturer (Dana, Chrysler, etc.).
3. Look at the door jamb sticker: The sticker on the driver's side doorjamb sometimes lists some specifications, though it's less likely to specify the exact axle ratio.
4. Differential housing casting number: This number can be used to look up the axle ratio and other specifications, but requires a parts catalog or online database. It's located on the differential housing itself.
5. Measure the driveshaft revolutions: This is the least accurate method. You would turn the driveshaft a certain number of rotations and count how many times the wheel rotates. The ratio between these will give you the axle ratio, but this is difficult to do accurately and requires special tools.
The most reliable method is to decode the VIN. Use a free online VIN decoder and enter your truck's VIN. This will give you the most accurate information about your vehicle's specifications.
