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3.42 vs 3.73 Rear Axle Ratio:(Why Gear Comparison is Important?)

The axle ratio also referred to as the gear ratio, is an important element to focus on when purchasing a pickup truck. Together with suspension, transmission, and engine, it dictates the overall performance of your truck.

With an understanding of how important it is to your truck; you can perfectly pick the configurations that suit your needs. In this article, I will focus on the 3.42 vs 3.73 rear axle ratio comparison and how each can be effective.

“Your axle ratio selection determines the output you receive from your truck. Some gear ratios will enable you to accelerate faster with fewer rotations while others will produce less power with more rotations.”

What Rear Axle Ratio is Best?

There are several factors to consider when choosing the best rear axle ratio and they include, towing capacity, acceleration when the truck is loaded and when empty, fuel economy, and cruising speed.

In this case, if you are looking forward to a higher cruising speed and better fuel efficiency, the 3.42 axle ratio will fit you well but if you want more acceleration and torque, the 3.73 axle ratio is your option.

Moreover, after depth research we found the best gear ratio is 3.55 with high acceleration.Since, 3.55 gear ratio is an even balance with high power and your desired fuel economy.

Understanding The Gear Ratios

The gear ratio represents the number of teeth in transmission, and it determines the number of revolutions the driveshaft makes in one rotation of the wheel.

For instance, if a vehicle has a 3.42 gear ratio, it means the driveshaft revolves 3.42 times in one turn of the wheel.

According to the general rule of thumb, the higher the axle ratio, the more the towing capacity and the greater the torque and acceleration.

That is why you will find heavy-duty pickup trucks and racing cars having a higher gear ratio. They generate more torque and horsepower.

They require fewer revolutions per minute to accelerate from 1 to 60 and can quickly hit top speed.

However, vehicles with a higher axle ratio have a slower top speed. On the contrary, vehicles with a lower axle ratio will hit a higher cruising speed but will not accelerate as fast.

In this context, if two vehicles that differ in gear ratios were to compete in a race, the outcomes at a stationery start are likely to be different compared to outcomes at a rolling start.

Although other details may emerge, this explanation is enough to make you understand more about gear ratios.

What is the Difference Between the 3.73 and 3.42 Axle Ratio?

Although some noticeable differences can be observed in the 3.42 vs 3.42 rear axle ratio, both can be considered heavy-duty axle ratios and they can easily be found in Chevy Silverado trucks. They have great pulling power.

However, when it comes to the taking off speed and the 1 to 60 time, the difference is evident.

In a city driving or drag racing, the 3.73 will easily maneuver compared to the 3.42 gear ratio.

Also, when driving for long distances on a highway, the story changes as soon as the 3.73 gear ratio hits top speed allowing your vehicle to hit higher cruising speed and giving you better fuel economy.

On the other hand, the 3.42 gear ratio will help you balance fuel efficiency and acceleration under the same circumstances.

If you are a regular highway and city traveler but occasionally need to haul heavy loads, the 3.42 gear will serve you best.

If you regularly do heavy-duty towing as you enjoy more acceleration, the 3.73 gear fits you well.

How Do I Know My Rear Axle Ratio?

Knowing your rear axle ratio is important, especially when you want to select the right gear configuration in transmission when upgrading your transmission, when calibrating the speedometer gear in your transmission, or when seeking professional assistance with a new axle ratio for your application.

There are different ways in which you can identify the axle ratio in your vehicle:

01. Do a Driveshaft Turn Test?

Lift the rear end of your vehicle on a hydraulic lift or jacks and turn one of the rear wheels. Use chalk, tape, or soapstone to mark the driveshaft where it meets the rear pinion.

Mark the tire as well. Rotate the marked tire once and count the number of times the drive shaft rotates in one spin.

For example, if the driveshaft revolves 3¾ times, that will translate to a 3.73 axle ratio.

02. Check the Axle and Differential cover

If the first method does not yield results, check the rear axle and the differential cover. You may find a sticker or a small metal plate with the gear ratio printed on it.

However, spotting the gear ratio can be challenging if the axle and differential covers are damaged or rusted.

03. Calculate the Ring and Pinion Teeth

Open the rear axle and count the number of teeth on the pinion and the ring gear.

Divide the large number (ring gear teeth) by the smaller number (pinion gear teeth) to find the axle ratio. In some cases, the number of teeth is stamped on the ring gear.

Are 3.73 Gears Good for 35″ Tires?

There is a direct correlation between gear ratio and tire size and different trucks are designed to be operated with specific tire sizes to maintain overall performance.

Changing a tire size may have different effects on different trucks depending on the uses.

That is why some people change both the tire size and gear ratio at the same time to get the optimum power ratio of their vehicle while others will only change tire size without altering the gear ratio and still get the same optimum power ratio.

Increasing tire size to 35 for a 3.73 gear ratio reduces the power limit of your vehicle and you can only drive on the flat, town, and highways plus irregular towing.

If your towing needs are regular and on steep hills, you will have to upgrade your gears to match the tire size and to avoid crushing your transmission.

Is a 3.42 Axle Ratio Good for Towing?

The higher the gear ratio, the more the towing capacity and the lower the fuel economy and vice versa. There are some factors to consider before concluding whether a 3.42 axle ratio is good for towing.

Such factors include the towing capability of your vehicle engine, tire size, the speed you will be towing at, the weight to be towed, the terrain of the area towing will happen, and the transmission gear ratios as each one of them will contribute to the overall towing capacity.

The 3.42 gear ratio may be sufficient or insufficient depending on your needs.

It is a good ratio if you are occasionally towing slightly heavier loads on flat ground areas and will give you better fuel economy.

But if you intend to tow heavy loads more often, you need a higher gear ratio such as the 3.73 or more.

However, if you are looking toward balancing towing and fuel efficiency, you might consider a standard ratio like 3.55 (out of this context).

It is the best towing ratio for most of the post-2010 pickup trucks.

How Do I Choose an Axle Ratio?

Whether you want to upgrade your axle ratio or you are shopping for a new truck, whatever configuration you settle for will affect your truck’s performance and the ability to tow and haul.

Here are some considerations that will help you in choosing the appropriate axle ratio according to your needs:

01. Towing Capacity

A truck’s tow and haul ratings are determined by the axle ratio. When you understand the use of your truck, you will choose an axle ratio that matches that.

If you enjoy sporty speeds and you rarely tow heavy loads, a vehicle with a lower axle ratio will carry you a long way.

If you are an off-road person, driving up on hills, traversing rough terrain, and hauling large loads, consider a higher axle ratio.

What you plan to tow vs the pickup truck tow rating should guide you in choosing the right axle ratio.

Follow this link for more information on towing capacity and gear ratio:

02. Fuel Efficiency

When looking at fuel efficiency, consider the weight to be towed or hauled, the nature of the roads you to be traveled, and your speed expectations.

Your focus should be to keep the engine at the lowest RPM for a set speed no matter the weight of the load you are towing or hauling.

Consider the load you want to tow or haul when driving at your preferred top speed and the fuel efficiency you want to achieve.

A lower axle ratio will give you a driving experience that will enable you to tow or haul the load at high speeds yet with a slightly high engine RPM, unlike a higher axle ratio.

Therefore, if you want to drive at a high rate of speed while still maintaining low RPMs, go for a smaller numerical axle ratio.

03. Powertrain

The kind of powertrain that your truck has will also determine your axle ratio requirements.

With a powerful engine that gives you more torque, you may not necessarily need a higher numerical axle ratio to tow and haul huge loads on tough terrains.

That extra power will carry your truck a long way even with a lower axle ratio.

Diesel engines are known to have more torque compared to gas engines; therefore, consider the kind of powertrain you are going to be working with.

04. Tire Size

Every pickup truck has a set of final drive ratio that is determined by axle ratio and transmission. Manufacturers optimize the final drive ratio for fuel economy and the overall performance of the vehicle.

Axle ratio and tire diameter contribute to the acceleration and the overall performance of your truck.

A change in tire diameter will have an impact on axle ratio. An increase in tire size should be accompanied by an increase in axle ratio in an equal measure.

However, you may be adding rotating mass which reduces efficiency and negatively changes the dynamics of the vehicle for which it was designed.

That is why most manufacturers do not encourage changing tire size as it alters the handling and performance of the vehicle.

Frequently Asked Questions (FAQs)

How Important is an axle ratio?

An axle ratio is more than just a numerical figure as it influences different functions of your vehicle from torque to fuel efficiency, towing capabilities and many more.

The axle ratio you chose determines the amount of fuel your vehicle consumes when speeding on highways and the torque relayed on tough terrain.

What axle ratio is better for bigger tires?

An increase in tire size lowers the final drive ratio which causes the engine to function outside the RPM range resulting in sluggish performance and a reduced fuel economy.

To have an ideal axle ratio that matches your bigger tires, increase the axle ratio with the same percentage you increased the tire size with to maintain your truck’s overall performance.

There are many aftermarket gear ratios to compensate for a variety of tire sizes.

Can I change my axle ratio?

When purchasing a pick truck, go for the axle ratio that suits your needs.

But if you realize later that your axle ratio is no longer serving you as you intended or changed your tire’s diameter, there is a need to change the axle ratios.

Most pickup trucks are sold with optional axle ratio upgrades, and you can choose from the options though it can affect the overall performance of your truck.


Understanding axle ratios before buying a truck helps you in choosing the right axle ratio for the jobs you want to be doing with it.

The 3.42 vs 3.73 rear axle ratio comparison is enough to give you a clear picture of what to expect with a lower or a higher axle ratio.

When you choose the right axle ratio from the beginning, you escape the burden of upgrading later in the future.

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