What is the rear axle ratio for a truck?

Axle ratio is an easy concept to understand once you understand the basics of how it works. Depending on the type of truck you are looking for and the purpose it will serve, the axle ratio plays an essential role in its overall performance.

Whether it is an all-wheel drive, front-wheel drive, rear- wheel drive, or four-wheel drive, axle ratio is a crucial factor to consider when purchasing a truck. Often, many car manufacturers offer the option to upgrade the rear axle ratio for a truck to increase its acceleration. Therefore, what is the rear axle ratio for a truck?

What is rear axle ratio?

Rear axle ratio is the overall number of revolutions the driveshaft or output shaft makes to spin the axle one complete rotation. It refers to the number of gears in a truck’s differential, the machine that links the driveshaft to the rear axle and then to the engine.

Expressed in the form of ratios, such as 3.42:1, this number denotes that the driveshaft turns 3.42 times for each wheel turn. However, this ratio is usually referred to as 3.42, or simply ‘three forty-two.’

Differentials and axles have gears that allow power transfer from the driveline and engine to the wheels of the truck. The transmission and engine turn a driveshaft that’s linked to a durable pinion gear within the axle.

In turn, the pinion gear links and turns the ring gear, which is connected to a differential case that has many smaller gears that send power to the wheels.

Generally, as the rear axle ratio number goes up, the lesser the fuel economy and the more its towing capacity increases. Lower numerical rear axle ratios mean the lesser the energy the truck utilizes when cruising on highways; thus, an increase in fuel economy.

What does rear axle 3.42 ratio mean?

Rear axle ratio is often a simple ratio, like 3.42. When a truck’s rear axle ratio is 3.42, it means its drive shaft and pinion gear has to revolve 3.42 times to turn the axle shafts once. Similarly, when a truck has a 4.10 gear ratio, it means the pinion gear and the drive shaft has to spin 4.10 times for a complete axle shaft rotation.

How to know the axle ratio of a car?

Calculating a vehicle’s axle ratio involves counting the number of teeth on the pinion gear as well as the ring gear and dividing the ring gear’s teeth number by the number of pinion gear teeth.

Luckily, modern trucks come with a sticker on the outside of its differentials, where you can easily find axle information.

Alternatively, you may also opt to lift the vehicle in the air and put it on neutral to ‘roughly’ see how many revolutions the driveshaft makes for a complete axle rotation.

This observation will provide an estimated figure since you will find the closest axle ratio to your number. For example, if you count four revolutions, then you most likely have a 4.10 axle ratio.

Is it better to have a higher or lower gear ratio?

Axle ratio directly affects a truck’s towing capacity, fuel economy, and torque. A truck with a high axle ratio number means more towing capacity, decreased fuel economy, and a lower top speed.

More mechanical power of the engine’s available torque is sent to the rear tires, improving off-the-line acceleration and more power for pulling heavy trailers and hauling hefty loads.

A truck with a low axle ratio number means the vehicle will go faster and improved fuel economy, but lower towing capacity. The vehicle’s engine will work less when speeding on highways.

A vehicle with a lower numerical axle ratio is said to have a high gear or high rear end ratios while vehicles with a higher numerical ratio have low gear or low rear end ratios. Therefore, trucks with high gear ratio are best for cruising while those with low gear ratios have fast acceleration.

Whether it is better to have a higher or lower gear ratio depends on what purpose your truck will serve. If you are looking for a truck to carry heavy loads or pull heavy trailers, you will need one with a lower gear ratio as it has more towing capacity and vice versa.

A small engine truck has a low gear ratio to give it adequate acceleration, while a high-powered engine truck has a high gear ratio to provide relaxed cruising at higher top speed.

Similarly, trucks with short tires require a high gearing ratio to travel the same distance as a taller-tired truck. This means their engines need to produce more power and this is only possible by increasing the gear ratio.

What is the best gear ratio for towing?

Typically, gear ratios intend to balance performance, fuel economy, and the vehicle’s capability. Automakers select a final drive ratio that lowers the engine’s rpm; thus, efficiently meeting the government’s mileage standards.

Optional axle ratios give more towing ability by increasing the engine’s available torque delivered to the axles. If you are looking for a truck for towing, the highest possible axle gear ratio is what you need.

A numerically higher axle ratio knocks off about a mile per gallon from the truck’s fuel economy. Therefore, a car with optional 4.30 gears will tow a heavier trailer than one with optional 4.10 gears.

Conclusion

It is crucial to consider the purpose a truck will serve before approaching a dealership to purchase one. Similarly, it is vital to understand the rear axle ratio for a truck and how it affects its overall capability.

Understanding your hauling needs and the concept of rear axle ratios for trucks is crucial. It helps you purchase a vehicle that is more suitable for your needs.

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