# What is Axle Ratio, and Why Does It Matter?

Car enthusiasts know that understanding axle ratios is important. However, not everyone knows what an axle ratio is and why it matters. In this article, we will define an axle ratio, how it is calculated, and why it matters for truck owners.

Contents

## Defining the Axle Gear Ratio

The axle gear ratio is a numerical representation of how much torque your engine produces in relation to the size of your tires. In simpler terms, it is the ratio of the driveshaft’s revolutions to that of the wheels’, determining how many times the driveshaft must rotate to turn the wheels once. The axle gear ratio affects a vehicle’s fuel economy and towing capacity.

## Calculating the Axle Gear Ratio

The axle gear ratio is calculated by dividing the driven gear’s teeth by the driving gear’s teeth, which are connected by an axle or chain. This figure determines how efficiently power from the engine is transferred, enabling comparisons between different types of engines and vehicles. Today’s vehicles typically have axle gear ratios ranging from 3.08-3.42.

## Expressing the Axle Gear Ratio

The following are the most common ways to express the axle gear ratio:

• Comparing input speed and output speed (i=Ws/We).
• The number of teeth on a ring gear is divided by the number of teeth on a pinion gear (T=Tg/Tp).
• The slippage ratio (S=Ns/Ne) measures the ratio in terms of rotational speed and not directly by gears.
• The driving gear’s number of teeth by the driven gear’s number of teeth (i=Ze/Zs).
• As a ratio or proportion (R=N1/N2), such as 4:1 or “four-to-one.”

## Finding Axle Ratios

To find your vehicle’s axle ratio, count the number of teeth on the ring gear and pinion or look for a sticker outside the differential. The sticker usually contains information about the axle ratio, which can be identified from its code. It is recommended to check the manufacturer’s website for further details if necessary.

## Selecting the Best Axle Ratios for Trucks

Selecting the best axle ratio for a truck can be a daunting task. However, understanding these factors in determining the ideal axle ratio can make this decision easier.

#### Fuel Economy: Lower Ratios Burn Less Fuel

When choosing the appropriate axle ratio for your truck, fuel economy should be one of your primary considerations. Lower ratios tend to burn less fuel, which saves money and environmental resources. The ideal axle ratio depends on the application. Heavier trucks require higher torque-to-weight ratios, while lighter trucks benefit from higher top speeds. Experts who understand truck engine capabilities can help balance torque output against fuel economy. Ultimately, the most cost-effective axle ratio should fulfill all driving needs while optimizing fuel efficiency.

#### Performance: Higher Ratios Provide Faster Acceleration

Performance is another critical factor when choosing the best axle ratio for your truck. Higher ratios for your axle provide faster acceleration than lower ratios, making them ideal for those who require good low-end power from their vehicle. With a higher ratio, you can expect more torque from less engine speed, reducing fuel consumption and tire wear. It is important to note that higher ratios increase noise levels and may not be suitable for all uses.

#### Towing: The Ideal Range for V8 Gas and Diesel Engines Is 3.55-3.73

Towing capacity is also critical to consider when selecting the best axle ratio for your truck. V8 gas and diesel engines are among the best options for towing. An axle ratio of 3.55-3.73 offers an outstanding balance between performance and tow power, making it suitable for most applications. With this range, you have good acceleration from low speeds and plenty of torque for mountain driving and towing heavy loads. Diesel-powered V8 engines may require a higher final drive ratio, such as 3.73 or higher, to meet their hauling needs, providing more power and torque at lower engine RPMs.

#### Trucks With Lower Ratios (3.31) Can Also Be Good Towers With Certain Transmission Types

While a higher ratio (4.10) is ideal for maximizing acceleration and hauling needs, those looking for better fuel efficiency should opt for a lower ratio (3.31). Lower ratios can still provide adequate power and torque for towing or hauling depending on the transmission type- such as manual or automatic. As a result, lower ratios can be an attractive option for both consumer and commercial-grade trucks.

## Conclusion

Understanding axle ratios is essential for truck owners as it affects their vehicle’s fuel economy and towing capacity. By calculating the axle gear ratio, expressing it in different ways, and finding the axle ratio of your car, you can select the best axle ratios for your truck based on its fuel economy, performance, and towing capacity.

Sources: