Transfer Case Ratio Calculator

Calculate transfer case low-range ratio effects on crawl speed, grade ability, and wheel torque for off-road vehicles.

Input Parameters

Results

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Overall Crawl Ratio
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Wheel Torque
lb-ft
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Crawl Speed @ Idle
mph
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Max Grade Ability
%
Note: Crawl ratios of 40-60:1 are typical for trail use. Rock crawlers run 80-100:1+. The Rubicon uses 4.0:1 low range. Maximum grade ability assumes adequate traction. SAE J2807 towing/grade standards.

Reference

Crawl Ratio = Low_range × 1st_gear × Final_drive Wheel Torque = Engine_T × Crawl × Efficiency (85%) Crawl Speed = (Idle_RPM / Crawl) × Tire_circ × 60/5280 Tractive Force = Wheel_torque / Tire_radius Max Grade = arctan(Force / Weight) × 100%