Rear Differential Ratio Calculator
A Zeemods utility designed to help you determine a suitable rear differential ratio for use with American Truck Simulator, built around Eaton transmission data and intended to complement Zeemods drivetrain content.
This tool is designed around Eaton transmission data. It is not intended to produce realistic results for unrelated transmission families.
If you need realistic tire data, check the truck garage and use a wheel/tire mod with proper real-world specifications shown in-game.
Calculator
Launch the calculator in a separate tab, then follow the prompts. The result should be treated as a practical setup reference rather than a universal drivetrain rule.
The calculator works best when opened directly, as it needs normal keyboard input and can be interrupted by embedded browser verification when loaded inside the store page.
Launch CalculatorOperation types
Choose the operation type that best matches the truck’s intended use. Different applications typically favour different axle ratio ranges.
Best suited to long-distance highway work, where fuel efficiency and steady cruising are priorities. This usually favours lower numerical axle ratios to reduce engine RPM at road speed.
A middle-ground option for varied driving, balancing flexibility, fuel efficiency, and pulling ability for mixed routes and more frequent stop-start operation.
Best for heavy work where torque multiplication matters most. This typically favours higher numerical axle ratios to help with pulling power and difficult terrain.
A lower numerical ratio generally reduces cruise RPM and can improve highway efficiency. A higher numerical ratio generally improves pulling ability and low-speed control, especially with heavier loads.