Ford Speedometer Gear Calculator

Speedometer Gear Equation:

\[ \text{Gear Teeth} = \frac{\text{Drive Teeth} \times \text{Axle Ratio} \times \text{Tire Revs per Mile}}{1001} \]

Drive Teeth (teeth):

teeth

Axle Ratio (decimal):

ratio

Tire Revs per Mile (revs/mile):

revs/mile

Required Speedometer Gear Teeth:

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1. What is the Ford Speedometer Gear Calculation?

The Ford speedometer gear calculation determines the correct number of teeth needed on the speedometer gear when changing tire sizes or axle ratios. This ensures your speedometer remains accurate after modifications.

2. How Does the Calculator Work?

The calculator uses the Ford speedometer gear equation:

\[ \text{Gear Teeth} = \frac{\text{Drive Teeth} \times \text{Axle Ratio} \times \text{Tire Revs per Mile}}{1001} \]

Where:

Drive Teeth — Number of teeth on the drive gear
Axle Ratio — Vehicle's rear axle ratio
Tire Revs per Mile — Number of revolutions your tire makes in one mile
1001 — Ford's constant for speedometer calibration

Explanation: The equation calculates the proper driven gear tooth count to maintain accurate speedometer readings after drivetrain or tire changes.

3. Importance of Correct Speedometer Gear

Details: An accurate speedometer is crucial for proper vehicle operation, safety, and avoiding speeding tickets. Incorrect gear selection can cause significant speedometer error.

4. Using the Calculator

Tips:

Drive teeth typically range from 6-8 teeth for most Ford vehicles
Axle ratio can be found in your vehicle specifications or on the axle tag
Tire revs per mile can be calculated from tire size or found in manufacturer specifications

5. Frequently Asked Questions (FAQ)

Q1: Where can I find my current drive gear tooth count?
A: The drive gear is located on the transmission output shaft or speedometer cable. Tooth count is often marked on the gear.

Q2: What if my calculated gear teeth isn't a whole number?
A: Ford makes gears in whole tooth increments. Round to nearest available gear (typically available in 1-tooth increments from 16-21 teeth).

Q3: How do I find tire revs per mile?
A: Use a tire size calculator or look up your specific tire model's revs per mile from the manufacturer.

Q4: Does this work for all Ford vehicles?
A: This applies primarily to older Ford vehicles with mechanical speedometers (pre-1990s). Newer electronic speedometers may need different calibration.

Q5: What's the 1001 constant in the formula?
A: This is Ford's calibration constant that accounts for the speedometer head gearing ratio and other factors in their mechanical speedometer design.