Off Road Gear Ratio Calculator

Crawl Ratio Formula:

\[ \text{Crawl Ratio} = \text{Low Gear} \times \text{Transfer Low} \times \text{Axle Ratio} \]

Crawl Ratio:

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1. What is Crawl Ratio?

The crawl ratio is a measure of a vehicle's off-road capability, representing the total gear reduction from the engine to the wheels. It determines how slowly a vehicle can move in its lowest gear, which is crucial for technical off-road driving.

2. How Does the Calculator Work?

The calculator uses the crawl ratio formula:

\[ \text{Crawl Ratio} = \text{Low Gear} \times \text{Transfer Low} \times \text{Axle Ratio} \]

Where:

\( \text{Low Gear} \) — Transmission's lowest gear ratio (dimensionless)
\( \text{Transfer Low} \) — Transfer case low-range ratio (dimensionless)
\( \text{Axle Ratio} \) — Differential gear ratio (dimensionless)

Explanation: The crawl ratio multiplies all the gear reductions in the drivetrain to give the total reduction from engine RPM to wheel rotation.

3. Importance of Crawl Ratio

Details: A higher crawl ratio allows for better control in technical terrain, improved torque at very low speeds, and reduced brake usage on steep descents. Typical values range from 20:1 for street vehicles to 100:1 or more for serious off-road rigs.

4. Using the Calculator

Tips: Enter your vehicle's transmission low gear ratio (often around 3-4:1), transfer case low range ratio (often 2-4:1), and axle ratio (common values 3-5:1). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's considered a good crawl ratio for off-roading?
A: For moderate off-roading, 40:1 is decent. Serious rock crawling typically benefits from 70:1 or higher.

Q2: Can I improve my crawl ratio?
A: Yes, by changing any of the three components: installing lower transmission gears, a transfer case with lower gearing, or higher numerical axle gears.

Q3: Does tire size affect crawl ratio?
A: While not part of the calculation, larger tires effectively reduce your crawl ratio by increasing the distance traveled per wheel revolution.

Q4: What's the difference between crawl ratio and overall gear ratio?
A: Crawl ratio specifically refers to the lowest possible gearing, while overall gear ratio can refer to any gear combination.

Q5: Why is crawl ratio important for off-roading?
A: It allows precise throttle control at very slow speeds, reduces strain on the drivetrain, and provides more torque to the wheels when needed most.