What Is Axle Ratio in Trucks?

A vehicle’s differential distributes power to the drive wheels and provides an additional gear that increases the amount of torque at the cost of rotation speed. The axle ratio is essentially the gear ratio of a vehicle’s differential. The axle ratio expresses the number of revolutions that the driveshaft must spin to spin the drive wheels once. This number is typically presented as a ratio. For example, 3.42:1 would mean the driveshaft would need to turn 3.42 times to spin the wheel once.

The axle ratio is critical in trucks since their axle ratio is essentially a final transmission gear. The axle ratio can affect a truck’s acceleration, fuel economy, and carrying capacity. Vehicle manufacturers offer several axle ratios for trucks since the appropriate axle ratio can vary depending on the vehicle’s intended use.

How Does Axle Ratio Affect Vehicle Performance?

An axle ratio that has a value of around 3.55:1 to 3.73:1 will allow your vehicle to accelerate faster and tow heavier loads. This is because a higher axle ratio means the differential will use a larger gear to spin the wheels. A bigger gear allows the wheels to have more torque, letting it carry heavier loads. However, this comes at the cost of fuel economy since the engine will have a much higher RPM. The gears will also be a lot shorter, which means the transmission is going to shift through the gears much faster.

Conversely, trucks with lower axle ratios like 3.31:1 to 3.55:1 will generally lead to better fuel economy since the engine can cruise on the highway at a lower engine RPM. However, trucks with lower axle ratios will accelerate slightly slower and won’t be able to carry as much load.

Is There an Ideal Axle Ratio?

Manufacturers typically have a standard axle ratio, which they claim has been carefully selected to provide a good mix of performance, towing strength, and efficiency. This might be the ideal axle ratio for many people. For example, the GMC Sierra 1500 has an axle ratio of 3.42:1, while Chevrolet pickup trucks use a similarly balanced axle ratio that slightly leans towards efficiency. 

That said, the ideal axle ratio for you will still depend on your application. If you regularly use your truck to carry heavy loads or trailers, then a higher axle ratio will allow you to accelerate faster and climb hills easier with heavy loads. A higher axle ratio can also be more favorable for people who want to have a truck that has nimble acceleration. However, if you’re someone who uses their truck as an everyday driver, only occasionally carries heavy loads, and values fuel economy, then the manufacturer’s standard ratio might be your best option.

How to Find Your Truck’s Axle Ratio

If you want to know your truck’s axle ratio, you can do so by finding the sticker located outside your differential. If you own a Ford vehicle, you’ll need to visit the RV and Trailer Towing Guide on their website and search for your vehicle’s model year. You’ll be able to find the axle ratio in the table.

You can also count the number of teeth on the ring gear and the pinion. Divide the number of the ring gear’s teeth by the number of the pinion’s teeth. This will give you the axle ratio.

Tips for Choosing Your Ideal Axle Ratio

The prescribed characteristics of an axle ratio number can also vary between manufacturers. Axle ratios and their effects can’t be compared across vehicle manufacturers because of varying tire sizes, which essentially serve as the final gear in the system. Axle ratios will also fluctuate as truck manufacturers create transmissions with more gears. More gears give trucks more gear ratios to choose from. This allows trucks to have short gears for when they need to carry heavy loads, as well as long gears for when they need to be efficient on the highway.

A transmission with more gears, for example, might allow a truck manufacturer to offer a larger rear axle ratio (a 3.70 instead of 3.45) while providing increased towing and carrying capabilities.

You should check the towing and payload tables on the manufacturer’s website. Manufacturers can also assist customers in selecting the best powertrain for their unique requirements. You should also compare axle alternatives within a single brand to see how each one affects the towing ratings provided in that brand’s towing guide.

Finding the appropriate axle ratio for your next truck can be just as crucial as picking the right engine and drivetrain options. It can make a significant impact on the truck’s capability and fuel economy. That said, it might be good not to fixate on the numerical value too much and instead refer to the towing and payload guides offered by manufacturers. Just remember to keep in mind the truck’s intended use when selecting your truck’s axle ratio.