What gear ratio is my transmission?

The gear ratio of your transmission is a crucial piece of information that can help you understand your vehicle's performance and capabilities. In simple terms, the gear ratio refers to the relationship between the number of rotations of the input shaft (connected to the engine) and the number of rotations of the output shaft (connected to the wheels).

What is Gear Ratio?

The gear ratio is a numerical value that represents the number of times the input shaft rotates for every single rotation of the output shaft. For example, a gear ratio of 3.45:1 means that the input shaft rotates 3.45 times for every single rotation of the output shaft.

The gear ratio is important because it determines the amount of torque and speed that is transferred from the engine to the wheels. A higher gear ratio, such as 4.10:1, will provide more torque to the wheels, making it easier to accelerate or climb hills, but at the expense of top-end speed. A lower gear ratio, such as 3.23:1, will result in a higher top speed but less low-end torque.

Determining Your Transmission's Gear Ratio

To determine the gear ratio of your transmission, you can consult your vehicle's owner's manual or look up the information online based on your make, model, and year. Alternatively, you can have a mechanic or transmission specialist inspect your vehicle and provide the specific gear ratio information.

Understanding the Importance of Gear Ratio

Knowing your transmission's gear ratio is important for several reasons:

• Performance: The gear ratio affects your vehicle's acceleration, top speed, and towing capacity. Choosing the right gear ratio can optimize your vehicle's performance for your specific needs.


• Fuel Efficiency: The gear ratio also impacts your vehicle's fuel efficiency. A higher gear ratio can result in better fuel economy at highway speeds, while a lower gear ratio may be more efficient for stop-and-go city driving.


• Customization: If you plan to modify your vehicle, such as by installing larger tires or a different rear axle, you may need to adjust the gear ratio to maintain optimal performance and drivability.

Understanding your transmission's gear ratio is an essential part of understanding your vehicle's capabilities and performance characteristics. By knowing this information, you can make informed decisions about how to best use and maintain your vehicle.

How do I find my transmission gear ratio?

The transmission ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. Alternatively, it can be calculated using the rotational speeds (RPM) or angular velocities (radians/sec) of the gears by dividing the input speed by the output speed, or the output speed by the input speed depending on the formula's convention. 
Using the number of teeth

• Formula: Transmission Ratio = Teeth on Driven Gear / Teeth on Driving Gear 
• Example: If the driving gear has 10 teeth and the driven gear has 20 teeth, the ratio is 20/10=220 / 10 equals 220/10=2, or 2:1. 

This video explains how to calculate gear ratios using teeth count: 59sMATH MADE EASY WITH LAURELYouTube · Mar 18, 2025
Using rotational speed

• Formula: Transmission Ratio = Rotational Speed of Driving Gear / Rotational Speed of Driven Gear 
• Example: If the driving gear rotates at 100 RPM and the driven gear rotates at 50 RPM, the ratio is 100/50=2100 / 50 equals 2100/50=2, or 2:1. 
• Note: This is an inverse relationship to the tooth count method. A ratio greater than 1 indicates an "underdrive," where the output shaft rotates slower than the input shaft, but with more torque. 

Where is the gear ratio stamped?

So let's zoom in here. You see that right there reads 411 which means 41 ring gear teeth 11 pinion teeth 41 divided by 11. Gives you 3.727.

How do you tell if you have 3.73 or 4.10 gears?

You can tell if you have 3.73 or 4.10 gears by manually counting, checking the differential cover for a tag, or finding the ratio stamped on the ring gear. The most direct method is to lift the rear wheels, rotate one tire one full revolution, and count how many times the driveshaft turns; 3.75 turns indicates 3.73 gears, while slightly over 4 turns indicates 4.10 gears.
 
This video demonstrates how to check your gear ratio by counting the driveshaft turns: 48sBent Motorsports OffroadYouTube · Sep 22, 2023
Method 1: Manual count (with the vehicle jacked up)

1. Jack up the vehicle: Safely lift the rear of your vehicle and secure it on jack stands. Ensure the wheels are off the ground. 
2. Mark the driveshaft and a tire: Place a mark on one of the rear tires and a corresponding mark on the driveshaft. 
3. Rotate the tire: Rotate the marked tire forward one full revolution. For an open differential, you may need to lift only one wheel and have someone hold the other stationary, or lift both wheels and rotate one tire twice while the other tire is on the ground. For a locked differential, lift both rear wheels and have one tire rotate once while the other rotates once in the opposite direction. 
4. Count the driveshaft turns: Count how many times the mark on the driveshaft has rotated. 
   • 3.73 gears: The driveshaft will turn approximately 3.753.753.75 times for one full tire revolution. 
   • 4.10 gears: The driveshaft will turn a little over 444 times for one full tire revolution. 

Method 2: Check the differential cover tag 

1. Locate the tag: Look for a small metal tag that is usually bolted to the differential cover. It may be on one of the bolts. 
2. Read the ratio: If the tag is still present, the gear ratio will be stamped on it. It will likely be a number like "3.73" or "4.10". 

You can watch this video to learn how to find the differential cover tag: 51sFlawed OffroadYouTube · Apr 18, 2022
Method 3: Read the ring gear stamps 

1. Locate the ring gear: This requires removing the differential cover to get a clear view of the ring gear.
2. Find the numbers: Look for two numbers stamped on the teeth of the ring gear, such as "41" and "11". 
3. Divide the numbers: Divide the larger number (teeth on the ring gear) by the smaller number (teeth on the pinion gear). 
   • 41÷11≈3.7341 divided by 11 is approximately equal to 3.7341÷11≈3.73 
   • 41÷10=4.1041 divided by 10 equals 4.1041÷10=4.10 

This video shows how to read the ring gear stamps to find the gear ratio: 46sJL LIFE OFFROADYouTube · Nov 18, 2022

Can I find my gear ratio with my VIN?

You may be able to tell the gear ratio from a vehicle's VIN by using an online VIN decoder, though not all manufacturers include this information in the VIN itself. If the gear ratio is included, it will likely be in the Vehicle Descriptor Section (VDS), which are the 4th through 8th digits of the VIN. For many vehicles, a sticker on the driver's side door jamb or on the vehicle's build sheet or owner's manual is a more reliable way to find the gear ratio. 
How to check the VIN

• Use an online VIN decoder: Enter the full VIN into a free online decoder. Some manufacturers have their own decoders, such as Mopar's decoder. 
• Look for the gear ratio code: Some VINs will have a code within the VDS that represents the gear ratio (e.g., "3731"). 
• Consult the manufacturer: If the VIN decoder doesn't provide the information, contact the vehicle manufacturer for assistance. 

Other methods to find the gear ratio

• Check the vehicle sticker: Look for a sticker on the driver's side door jamb or on the vehicle's build sheet. This sticker often contains detailed information about the vehicle's equipment, including the axle ratio. 
• Look at the differential: Some differentials have a metal tag with the gear ratio stamped on them, or there may be a sticker on the axle itself. 
• Consult your owner's manual: The owner's manual or other paperwork from the vehicle's purchase often lists the gear ratio.