Difference between 3.55 and 3.92 axle ratio

Automakers manufacture vehicles with different axle ratios, motor transmissions, drivelines, and torque. The different gearing options make all the difference in your vehicle’s performance; thus, the need to understand axle ratios. Standard axle ratio works well in your truck if you do not plan on using your truck for any heavy-duty hauling or for pulling trailers regularly.

To use your truck for hauling or towing a trailer requires you to understand axle ratios and how they affect your truck’s performance and overall fuel consumption. For instance, you should be able to explain the difference between 3.55 and 3.92 axle ratios.

What is the difference between 3.55 and 3.92 axle ratios?

Axle ratio refers to the gears in the differential of the truck, a mechanical device that connects the driveshaft to the rear axle and then to the engine. It is the number of revolutions the driveshaft or output shaft makes to the rear axle. Axle ratios are numerically expressed in a ratio, representing the number of teeth on the ring gear to the number of teeth on the pinion gear.

3.55 axle ratio
For example, a truck with a 3.55:1 gear ratio means that the output shaft has to turn 3.55 times for one complete rotation of the rear axle. Similarly, a vehicle with a 3.92:1 gear ratio means the driveshaft has to turn 3.92 times for one full wheel spin. Often written as only 3.55, instead of 3.55:1, both forms of axle ratios mean the same thing.

Fuel efficiency

Fuel economy is one of the most crucial factors to consider when buying a vehicle. Even when fuel prices are low, you do not expect them to stay down forever. Axle ratio contributes to the fuel efficiency of any vehicle. Automobile makers use axle ratio in transmissions to prevent your engine from operating within an unsafe and uneconomical operating rpm range. As the numerical digit of the axle ratio goes up, fuel economy goes down. For instance, a truck with an axle ratio of 3.55 burns less fuel at highway speeds than compared to that with 3.92 ratio.

Lower numerical axle ratios have better fuel economy because there are lesser revolutions per minute, meaning the vehicle accelerates much slower. Higher numerical axle ratios accelerate faster, meaning more RPMs, and less fuel economy.

Performance

determine my axle ratio

Different axle ratios affect the overall drivability of vehicles. The bigger the axle ratio number, the faster the vehicle can accelerate. For instance, a truck with an axle ratio of 3.55 will accelerate much quicker than a truck with an axle ratio of 3.92. It does not matter if the truck is carrying a load or not; it is pure mechanics.

Similarly, vehicles with higher engine power require higher axle ratio numbers to enable them to provide a higher top speed and relaxed cruising. Alternatively, vehicles with low engine power have lower axle ratios that provide adequate acceleration at highway speeds.

Towing ability

Generally, the standard towing axle ratio for trucks made post-2010 is 3.55 or 3.73. These ratios offer more than enough acceleration power with gas, whether diesels or v-8s. However, trucks with more than 8-speed automatics work better with lower axle ratios, such as 3.31. Newer transmissions, like those in 8-, 9- to 10-speed automatics, have a lower first and second gear than the older 4, 5, or 6-speeds, aiding in offsetting the axle ratio acceleration deficit.

Trucks with numerically higher axle ratios offer more mechanical advantage, sending more engine torque to the front tires, in cases of four-wheel-drive trucks, and to the rear tires. Therefore a truck with 3.92 axle ratio has better towing capability than one with 3.55 or 3.31 axle ratio. It will also consume more fuel due to the increase in the number of RPMs.

high gear ratio
Importance of knowing your axle ratio

One of the significant benefits of understanding the axle ratio is that it gives you a mechanical advantage. There will be a trade-off in rotational power, that is, between torque and speed. When the rear end gear ratio is 1:1, the amount of speed and torque is similar. Therefore, increasing the axle ratio reduces the amount of torque and significantly increases speed, and if you reduce the axle ratio, you reduce speed and boost the torque.

Conclusion

Axle ratio plays a huge role in your truck’s overall performance as well as fuel economy. It is responsible for improving the car’s towing capacity and improves its acceleration if adjusted appropriately. By understanding the difference between 3.55 and 3.92 axle ratios, consumers make better decisions when purchasing a truck; hence, buying one that best suits their needs.

For those towing trailers or hauling heavy loads, we recommend 3.73 or 4.10 axle ratios. Similarly, when driving a new truck, monitor the speedometer and your driving habits to maximize fuel economy. You will find that the truck has better performance when your lower gears work their magic, whether you are towing a trailer or not.

 

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