Gearing & drivetrain calculators
Engine rpm and speed in every gear, crawl ratio, and the axle ratio you have or need.
Before you change gears
- Know what you have. The axle ratio is on a tag on the axle cover or in the door or glovebox sticker; the transmission’s ratios are on its spec sheet.
- Measure the real tire. Engine rpm depends on overall tire diameter, and bigger tires make every ratio act taller.
- Decide on a cruising rpm. Work out the rpm at your usual highway speed in top gear, and pick the ratio that puts it where the engine is happy.
- Check what your axle is made in. Not every ratio is available for every axle, and some need a different carrier.