Transfer Case Ratio Calculator

The crawl ratio is the total gear reduction available to your 4WD vehicle in its lowest gear — a critical number for off-road driving over rocks, steep terrain, or obstacles that demand extreme slow-speed control. Select your Transmission Low Gear Ratio, Transfer Case Low Range Ratio, and Axle Differential Ratio, then enter your Tire Diameter to calculate your Crawl Ratio. Secondary outputs include Distance per Revolution, a Performance Rating, and a Best For summary of what your drivetrain setup is suited for.

inches

Check if using two transfer cases

Results

Crawl Ratio

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Distance per Revolution

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Performance Rating

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Best For

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Frequently Asked Questions

What is a transfer case ratio?

Transfer case ratio is the gear reduction provided by the transfer case in low range. It multiplies the torque from the transmission to provide better control at low speeds for off-road driving.

How do I calculate my crawl ratio?

Crawl ratio is calculated by multiplying transmission low gear ratio × transfer case low range ratio × axle differential ratio. For dual transfer cases, multiply by the second case ratio as well.

What crawl ratio is best for rock crawling?

For technical rock crawling, ratios of 70:1 to 100:1 are ideal. Higher ratios (100:1+) provide excellent control for extreme terrain, while 50:1-70:1 works well for moderate crawling.

What does distance per revolution mean?

Distance per revolution is how far your vehicle moves forward with each complete rotation of the engine. Lower distances mean more precise control and slower speeds for technical terrain.

Should I use dual transfer cases?

Dual transfer cases provide extremely high gear reduction ratios (often 200:1+) for the most technical terrain. They're typically used in competition crawling or extreme off-road situations.

How does tire size affect crawl ratio?

Larger tires effectively reduce your crawl ratio by covering more ground per revolution. Smaller tires increase the effective ratio, providing better low-speed control but reducing ground clearance.

What's the difference between 4Hi and 4Lo?

4Hi (high range) typically has a 1:1 ratio for normal driving speeds, while 4Lo (low range) provides gear reduction (usually 2:1 to 4:1) for maximum torque and control at low speeds.