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Build Planner / Crawl ratio

Crawl ratio calculator

First gear times low range times the axle ratio. The number that decides whether you idle down a ledge or ride the brakes, with how fast that actually is on your tires.

Your truck

Factory, a low range gear kit, or a case swapped in from another truck.

rpm

The tire only changes how fast you creep, not the ratio. A manual's crawler or first gear counts as first.

Add first gear, low range and your axle ratio.

How the numbers work

What is a crawl ratio?

The total gear reduction between the engine and the wheels in the lowest gear: first gear × transfer case low range × axle ratio. An FJ Cruiser automatic is 3.52 × 2.566 × 3.727, about 33.7:1. A Wrangler Rubicon with the 6-speed manual is about 84:1.

What's a good crawl ratio?

Around 40:1 handles most overland trails. 50 to 60:1 lets you idle down rocky descents without riding the brakes. Past 70:1 is rock crawling territory. Automatics get away with less, because the torque converter multiplies torque at low speed and lets you creep without stalling.

How does tire size change it?

It doesn't change the ratio, but a taller tire covers more ground per turn, so you creep faster and have less torque at the dirt. The creep speed here uses your tire, which is why a regear matters more after 35s than the ratio alone suggests.

How do I raise mine?

Deeper axle gears are the usual way, and they also fix highway RPM after bigger tires. Beyond that: a lower transfer case gear set (4:1 kits exist for many Toyota and Jeep cases), or a doubler or crawl box for the serious builds. Pick your truck and the list above shows the ones made for it, with what each does to your numbers.

Use at your own risk. These calculators are here to help you plan and to inform your decisions, not to sign off on a build. Many numbers are estimates worked out from factory figures, and some factory figures are not yet confirmed. Check every number against your own truck, its manuals and a qualified shop before you buy parts, cut, weld, lift, regear or drive on it. Long Range Desert Tools is not liable for anything you do based on these calculators or their results. The full terms are in our policies.