The quickest way to know is to read the axle ratio from official labels or build data tied to your VIN. Look for a 3.92 on the door sticker, the rear differential tag, or pull up the build sheet or window sticker through your VIN or dealer.
Where to look for the axle ratio
These are the most reliable sources you can check in person or obtain from RAM or a dealer. Start with the easiest check and move to the VIN-based method if you don’t find a label.
- Driver-side door jamb placard: Look for a line that lists the axle or ratio. It may read “Axle: 3.92” or show “3.92:1.”
- Rear differential cover tag or stamping: Some Ram models include a tag or stamp on the differential housing that states the gear ratio (e.g., “RATIO 3.92”).
- VIN-based build sheet or data sheet: Your VIN can be used to pull the factory build data, which lists the axle ratio as configured at production.
- Original window sticker (Monroney) or dealership invoice: The axle ratio is typically listed in the vehicle’s original paperwork under the drivetrain options.
- Dealer or RAM customer support: Provide your VIN and they can retrieve the exact axle specification from the factory records.
If any of these sources are legible, they should clearly indicate the axle ratio. If labels are missing or unreadable, VIN-based verification is the definitive method.
How to confirm with the VIN or a dealer
When label information isn’t available, use official data tied to your vehicle identification number (VIN). These steps help ensure you get the exact configuration for your RAM.
- Use a VIN decoder or RAM’s official lookup: Enter your VIN on a reputable decoder or RAM’s service portal to retrieve the axle code; the result will show the rear axle ratio if configured with that option.
- Request a build sheet from the dealer: The build sheet (or order sheet) lists all factory-installed options, including the rear axle ratio.
- Check the original window sticker via VIN: If you have access to the window sticker (even online copies), it will show the axle ratio under drivetrain/options.
- Reference RAM’s official customer support: If you’re unsure, a representative can confirm the exact axle configuration using your VIN.
VIN- or build-sheet verification is the most reliable way to confirm the exact rear axle ratio when physical labels aren’t available.
Understanding what 3.92 means for your RAM
Impact on performance and speed
A 3.92:1 rear axle ratio means the driveshaft must rotate about 3.92 times for the wheels to complete one revolution (the precise gearing affects torque, acceleration, and towing capability). Higher numeric ratios like 3.92 typically provide stronger low-end torque and better towing performance at the expense of higher engine RPM at highway speeds, compared with lower ratios such as 3.21 or 3.55.
How it interacts with tires and gearing
The effect of a 3.92 ratio is also influenced by your tire size and axle configuration (2WD vs 4x4, crew cab vs quad cab, etc.). Changing tire diameter without recalibrating the speedometer can alter indicated speed and engine RPM, so it’s important to account for Tires-Plus-Gears when calculating real-world performance.
Typical RAM configurations that carry 3.92
The 3.92 rear axle ratio is used on various RAM models and trims, including some 4x4 configurations and heavier work-truck setups. Exact availability depends on model year, drivetrain, and option packages. Always verify with the VIN/build data to be sure for your specific vehicle.
Bottom line and best practices
To confirm whether your RAM has a 3.92 rear axle ratio, start with the door jamb placard or the rear differential tag, then verify with the VIN-based build sheet or dealer data if needed. Knowing the exact ratio helps with speedometer accuracy, towing calculations, and matching replacement parts. If you’re planning mods or tire changes, double-check the axle ratio to ensure correct gearing and calibration.
Summary
In short, check legible labels first (door sticker or differential tag). If labels aren’t available, use your VIN to pull a build sheet or have a RAM dealer verify the axle ratio. The 3.92 figure indicates a gearing setup that prioritizes torque and towing capability, with considerations for tire size and speedometer calibration. Always confirm with official records for your exact vehicle configuration.