What is a 3.73 axle ratio good for?

A 3.73 axle ratio is a mid-range rear-end gear that balances everyday drivability with capable towing. In short, it offers stronger off-the-line response and hill-climbing ability than lower numerically geared setups, while not being as aggressively geared for towing or as fuel-thirsty at highway speeds as higher ratios.

How a 3.73 gearing changes your drive

Understanding the math helps explain the practical effects. A 3.73:1 final-drive means the engine turns about 3.73 times for every wheel revolution. That translates to more torque at the wheels and quicker acceleration from a stop or when pulling a load, but it also means the engine runs at higher RPMs at highway speeds compared with lower-numbered gears like 3.55 or 3.21. The net result is better low-end performance and hill-climbing ability, with a potential hit to fuel economy on long highway trips, depending on tire size and engine/transmission pairing.

Trade-offs for acceleration and towing

With a 3.73, you’ll typically feel stronger launch performance and improved climb-out when towing light to moderate loads. The trade-off is a bit more engine work at highway speeds, which can reduce mpg slightly versus a taller (lower numeric) gear. The exact effect depends on engine torque, transmission gearing, and tire diameter.

Impact on highway cruising and fuel economy

At steady highway speeds, the engine operates at higher RPM with a 3.73 than with a lower-numbered ratio. If you regularly drive long distances at speed with little towing, you might notice modestly higher fuel use. That said, modern transmissions and engines can minimize this difference, and real-world results vary by vehicle, speed, and tire size.

Best use cases

Drivers who want a practical balance between everyday driving comfort and the ability to tow or haul moderately should consider a 3.73. The following scenarios are where this ratio tends to shine.

• Moderate towing and hauling, such as small trailers, boats, or campers within a vehicle’s rated capacity.


• Everyday driving with frequent hills or mountain roads, where better low-speed torque helps with acceleration and negotiating grades.


• Vehicles with mid-range or smaller engines that benefit from increased wheel torque to feel responsive in city or suburban driving.


• 4x4 or off-road setups where reliable low-end performance aids crawling and ascent on inclines, while still keeping highway performance reasonable.

In practice, 3.73 is often considered the middle ground for pickups and SUVs that need to tow or haul occasionally but aren’t built for extreme payloads. It pairs well with many V6 engines and some smaller V8s, especially when a transmission with multiple gears can optimize the engine’s torque curve.

Considerations when choosing a 3.73 axle

Before selecting this gearing, weigh how heavy your typical loads are, your typical driving terrain, and how tire size interacts with your final drive. The following factors influence the real-world feel of a 3.73 setup.

• Engine torque and transmission gearing: More torque and a well-matched transmission can maximize the benefits of a 3.73.


• Tire diameter and wheel size: Larger than stock tires effectively raise the gearing, increasing RPM at speed and potentially reducing acceleration and economy.


• Payload and towing needs: If your loads are consistently heavy, you may prefer a lower numerical ratio (e.g., 3.55) or a higher one (e.g., 4.10) depending on the vehicle.


• Terrain and climate: Hilly or mountainous regions and frequent starts on grades favor a higher torque gear like 3.73; flat, long highway cruising may benefit from a taller gearing.

Consult your vehicle’s manufacturer specifications and consider a test drive with the gears adjusted (or simulated via tire size changes) to verify the effect on acceleration, braking, and fuel economy before committing to a swap.

Who benefits most

Vehicle profiles likely to benefit

Owners of mid-size or full-size pickups and SUVs that regularly tow or haul moderate loads tend to gain the most from a 3.73 axle. It’s a common choice for models equipped with mid-range engines (often V6 or smaller V8) where extra low-end torque improves daily usability without sacrificing too much highway efficiency.

• Trucks and SUVs used for light-to-moderate towing (up to the vehicle’s rated capacity).


• Vehicles that see mixed driving: city commutes plus occasional hills or mountain roads.


• 4x4 setups where predictable low-speed torque aids off-road traction without needing extreme low-range gearing.

For drivers who mostly drive highway with little to no towing, or for those who frequently travel long stretches at steady speeds, a taller gear like 3.55 or 3.31 may offer better fuel economy. Conversely, heavy-duty towing or extreme off-road crawling often benefits from gears like 4.10 or 4.56, depending on the vehicle and drivetrain configuration.

Summary

A 3.73 axle ratio serves as a practical middle ground that enhances low-end torque and acceleration for moderate towing and mixed driving, while keeping highway performance acceptable for everyday use. It’s a sensible choice for many trucks and SUVs that need occasional towing or hauling without stepping up to more extreme gearing. Always consider engine torque, transmission, and tire size, and verify with manufacturer guidance to ensure the setup matches your typical duties.

What's the best gear ratio for highway driving?

The best gear ratio for highway driving is typically a numerically lower one to keep engine RPMs low, which improves fuel economy and reduces noise. For a vehicle with an overdrive transmission, a ratio like 3.25 to 3.70 is often a good compromise, while a ratio around 3.42 is a common and efficient stock setting for modern vehicles. 
This video explains the basics of gear ratios and how they affect performance: 1mGearFX DrivelineYouTube · Feb 10, 2023
Common gear ratios for highway driving

• 3.25: A good choice for pure highway cruising and long road trips, especially with a non-overdrive transmission, as it keeps RPMs very low. 
• 3.42: A popular and well-balanced ratio often found in factory vehicles, offering a good blend of fuel economy and acceleration for daily driving. 
• 3.55: A good option for prioritizing fuel economy on the highway, though it sacrifices some acceleration compared to higher ratios. 
• 3.70: A strong compromise that provides a good balance between highway cruising and better acceleration for daily driving or occasional spirited driving. 

Factors to consider

• Transmission: Vehicles with an overdrive gear (where the driveshaft spins faster than the engine's output shaft) can use a numerically lower gear ratio and still achieve low highway RPMs. 
• Tire size: Taller tires require a numerically lower gear ratio to avoid excessively high RPMs at highway speeds. 
• Engine and vehicle weight: A more powerful engine or a lighter vehicle can handle a numerically higher ratio without a significant penalty to highway performance, while heavier vehicles may need numerically lower gears for better performance. 
• Driving goals:
  • Maximum fuel economy: Go with the most numerically low ratio possible. 
  • Balance of fuel economy and acceleration: Choose a ratio in the 3.55 to 3.70 range. 
  • Frequent towing or heavy loads: You will generally want a more numerically high gear ratio for more torque, but this will result in higher RPMs on the highway. 

This video explains how to choose the right gear ratio for your vehicle based on your needs: 56sLate Model Restoration (LMR)YouTube · May 18, 2025

Is a 3.73 ratio good for towing?

Yes, 3.73 gears are good for towing because their higher numerical ratio provides more torque, which improves performance when pulling heavy loads. While they offer better towing power and low-end acceleration, they result in higher engine RPMs, lower top speed, and poorer fuel economy compared to lower gear ratios like 3.55. 
This video explains the benefits of 3.73 gears for towing: 1mGetty's GarageYouTube · Jun 1, 2024
Advantages for towing

• More torque: The higher gear ratio gives the vehicle a mechanical advantage, translating more engine torque to the wheels for pulling heavy loads. 
• Better performance: They provide better performance for towing, especially for heavy loads and stop-and-go traffic, and are an upgrade for trucks with lower gears like 3.15 or 3.55. 
• Improved acceleration: They can improve off-the-line performance and acceleration, which is helpful when getting a heavy trailer moving. 

Disadvantages for towing

• Higher RPMs: The engine will operate at a higher RPM while cruising, which can lead to a less comfortable ride and worse fuel economy. 
• Lower top speed: The overall top speed is reduced. 
• Fuel consumption: Fuel economy is generally lower, especially on the highway, compared to a truck with a lower gear ratio. 

You can watch this video to see the effect of gearing on RPMs while towing: 58sGreat Lakes PowerstrokeFX4YouTube · Mar 14, 2025
When 3.73 gears may not be ideal 

• If you have a vehicle with a high-revving engine, like some V10s, 3.73 gears may keep the engine out of its optimal powerband, leading to a miserable towing experience, as detailed on Quora. 
• If your primary use is highway cruising and you rarely tow, lower gears like 3.55 are better for fuel economy and a quieter ride. 

What are the benefits of 3.73 gears?

The main benefits of 3.73 gears are improved acceleration and better pulling power, ideal for performance driving, off-roading, and towing. This is because they increase the torque sent to the wheels, allowing a vehicle to accelerate faster and handle heavier loads more effectively. The downside is that 3.73 gears can lead to lower fuel economy and higher engine RPMs at highway speeds compared to taller gears. 
Improved acceleration and performance 

• Increased torque: 3.73 gears provide more torque multiplication, which results in quicker acceleration from a stop and in the mid-range. 
• Better "off the line" feel: This gear ratio can make a vehicle feel much more responsive, especially when compared to lower ratios like 3.08 or 3.21. 
• More power in the powerband: For many vehicles, 3.73 gears place the engine in a more optimal powerband for street driving, making it feel less "lugging". 
• Good for racing/performance: The enhanced acceleration is ideal for drag strip performance or performance street driving. 

Enhanced towing and load-carrying capacity 

• Better for towing: The increased torque is beneficial for pulling heavy trailers, as it provides more pulling power. 
• Handles heavy loads: This gear ratio can be ideal for trucks that are regularly used for hauling or for off-roading with heavy equipment. 

Potential downsides

• Lower fuel economy: Because the engine runs at a higher RPM for a given speed, gas mileage often decreases, especially on the highway. 
• Higher highway RPMs: At highway speeds, you will likely be turning higher RPMs, which can increase engine noise and may be less desirable for long-distance cruising. 
• Potential overdrive pairing issues: If you have an overdrive transmission, 3.73 gears might need to be paired with the correct overdrive gear to balance highway cruising and city performance. 

Are 3.73 gears good for 35 tires?

3.73 gears are generally okay for 35-inch tires for daily, flat-terrain driving, but not ideal for performance, heavy towing, or mountainous areas. You'll likely experience a noticeable decrease in acceleration and fuel economy, and the vehicle may constantly shift gears on the highway. For a better experience, especially with aggressive off-roading or towing, a re-gear to a lower ratio like 4.10 or 4.56 is recommended. 
Downsides of 3.73 gears with 35-inch tires 

• Reduced acceleration: The larger tires create more leverage, making the engine work harder to get up to speed. 
• Poor fuel economy: You'll likely see a drop in gas mileage. 
• Transmission hunting: On the highway, the vehicle may have to downshift frequently to maintain speed, especially on inclines. 
• Strained drivetrain: The engine and transmission will be under more stress, particularly during heavy loads or towing. 

When 3.73 gears might be acceptable 

• Flat terrain: If you live in a mostly flat area, you may be able to manage without re-gearing. 
• Daily driving: If you're not concerned about performance and are using the vehicle for everyday driving, it can be a workable solution for a while. 
• Diesel engines: Vehicles with diesel engines have more torque and may handle the larger tires better, often without the need to re-gear. 

When you should re-gear

• If you plan to tow or haul heavy loads .
• If you frequently drive in hilly or mountainous areas .
• If you want better performance and acceleration .
• If you want to reduce strain on the drivetrain and avoid transmission issues .