A differential gear ratio calculator allows you to determine the effects of changing tire size, gear ratio and speed on engine RPMs in rear- and four-wheel drive vehicles. The differential gear ratio impacts vehicle speed, power and fuel economy and can be changed to increase one factor to the detriment of the others. Numerically higher ratios provide more low-end power, while numerically lower ratios give more top-end speed and fuel economy.
Changing differential gear ratio impacts engine RPMs, and a gear ratio calculator helps to determine the correct gear ratio to achieve a desired engine RPM range. Calculators such as the one available at YukonGear.com allow users to input constants such as desired ratio, tire height and speed to calculate engine RPMs with a variety of transmission types. YukonGear.com also provides factory-guided ideal engine RPM ranges to compare with the results of the calculation.
For applications such as moderate- or heavy-duty towing, a numerically higher gear ratio gives the engine more low-end power to make moving the heavier load easier on the transmission and engine. Changing tire size also impacts the engine RPM and the ability to deliver power to the wheels. A differential gear ratio calculator also allows users to calculate the impact of changing tire size while leaving other variables constant.