3.42 vs 3.73 Rear Axle Ratio (Gears Comparison Guide)

In this post, I am going to be doing a 3.48 vs 3.73 rear axle ratio comparison. I will explore which one works best for your particular situation and how to calculate the ratio best suited to your needs.

The rear-axle ratio is also known as the gear ratio. It, along with the engine and transmission determines just how much power output your vehicle will give out. To get a clearer understanding of how it works, in principle, we can use the gears on a racing bike or mountain bike.

The output you get varies based on your gear selection. Specific gears will allow you to accelerate faster with fewer rotations while others produce less power with significantly more rotations. At a basic level, this explains how gear ratios work in cars as well.

In short, the core differences are the 3.73 gear ratio gives you a lot more acceleration and torque, the 3.43 has a higher cruising speed and better fuel economy. The question of which one is the better option can best be answered by the specific application intended for your vehicle.

Understanding Gear Ratios

To bring it closer to home, the gear ratio of a car is determined by dividing the number of teeth on the ring gear by the number of teeth on the pinion.

The pinion is attached to the axle which gets its rotational power from the engine. The gear ratio also denotes the number of times the axle rotates to produce a single rotation on the wheels.

Generally speaking the higher the gear ratio, the more acceleration and torque you will get from the vehicle. That’s why you will find that racing cars and heavy-duty pickup trucks will have a higher gear ratio.

They produce more horsepower and torque. They need fewer RPMs to accelerate from 1 to 60 and can reach top speed much faster. However, the higher gear ratio means they also have a lower top speed. A lower gear ratio, on the other hand, will not accelerate as fast but can reach higher cruising speed.

This means that the results if you were to race 2 cars with different gear ratios, the results may be very different in a stationery start as compared to a rolling start. There are a lot more factors that come into play but this simplified explanation will give you a good idea of what it all means.

Is There a Big Difference Between 3.42 and 3.73 Gears?

As explained above, there definitely is a difference between the two though both could be considered heavy-duty gear ratios. You will find these on trucks like the Chevrolet Silverado, for example.

They have great towing capacity. The difference is noticeable when it comes to take-off speed and the 0-60 time. In a drag race or city driving, the 3.73 will definitely be at an advantage.

Give them a long stretch and the story will change as soon as the 3.73 reaches top speed. It means that the 3.73 is better suited for the highway with higher cruising speed and fuel economy.

What Rear Axle Ratio is Best?

Out of the context of this post, the best gear ratio is the 3.55 gear ratio. This is because it is an even balance fuel economy and power.

If you have a truck that you use for hauling, towing, and other heavy-duty stuff, this will be a good compromise. Looking at the two we are comparing in this post, the best gear ratio for you depends on what you want out of your vehicle.

If you have a daily driver that you use for city and highway driving at fairly regular intervals and you do the occasional heavy-duty stuff, the 3.43 is best suited for you. If fast acceleration, heavy-duty towing, and hauling capability is your thing, the 3.73 will be the ideal fit for you.

How Do I Know My Rear Axle Ratio?

There are several ways of telling what axle ratio you have on your car. The first way is to lift your car on jacks or a hydraulic lift then turn one of the rear wheels.

Look at how many wheel rotations it takes for the driveshaft to make a full rotation. This will show you the gear ratio. The second way is to look for a small plate that is bolted onto the rear axle cover.

It will have the axle ratio printed on it. Sometimes though, it may be rusted or damaged so that you can’t tell the axle ratio. In such cases, you could open up the rear axle and count the teeth on the pinion and ring gear.

Divide the wheel gear teeth by the pinion teeth. This will give you the ratio. In other cases, the gear ratio will be engraved on the pinion shaft of the ring gear.

How Do I Choose an Axle Ratio?

The gear ratio on any vehicle is determined based on several factors that include the engine size, transmission, ground clearance as well as tire size.

In situations where modifications are made on the vehicle, the axle may no longer be sufficient. A typical example is when you do a lift on your car or truck.

This involves new suspension and possibly bigger tires. These may overwhelm the current axle. Fortunately, there’s a way to calculate the right rear axle ratio. The formula is new tire size x old axle ratio divided by old tire size. This will give you the new axle ratio.

The answer to the question of whether or not one gear ratio is better than the other is answered by what specific need you have for your vehicle. Answering that will help determine which one is the best option for you.