Driveline Tools
Three precision tools for dialing in your driveline. Run the numbers before you wrench, get the right gear, the right crawl, and the right cruising RPM before parts hit the bench.
Whether you're regearing for taller tires, planning a transfer case swap, or just trying to figure out where your tach will sit at highway speed — these calculators do the math so you don't have to. Plug in your numbers, get instant answers.
Estimate engine RPM at a cruising speed.
For the Trail
Crawl ratio is the multiplied gear reduction at your slowest possible speed — first gear, low range, and your axle ratio combined. Higher numbers mean more torque, slower controlled crawling. Most daily drivers sit around 25:1; serious rigs run 70:1 or more.
Find your total reduction in low range.
Sizing Up Your Tires
Going from a 255/70R18 to a 285/75R17? That changes everything downstream, your effective gearing, your speedometer reading, your crawl ratio. Calculate the actual height first, then send it straight into the RPM calculator above.
Convert a tire size to overall diameter. e.g. 255/70R18