How Cummins axles enhance performance and reduce emissions
Axles play a crucial role in powering commercial vehicles, especially in heavy-duty applications where performance, reliability, and efficiency are vital. At Cummins Inc., we’re dedicated to delivering advanced components that enhance vehicle efficiency, improve performance, and reduce environmental impact. Our innovation in drivetrain and axle technology is centered around improving drivetrain efficiency, which supports Cummins’ Destination Zero strategy — our commitment to a more sustainable, low-emissions future.
The role of axles in vehicle performance
Drive axles are critical components in the drivetrain, the system that powers the vehicle. These axles transfer power from the engine through the transmission and driveshaft to the wheels. In commercial applications, axles perform several important functions:
- Supporting vehicle weight: Drive axles bear the load of the vehicle and its payload.
- Transmitting torque: They direct torque from the drivetrain to the wheels, enabling the vehicle to move.
- Optimizing performance: By matching the correct axle gear ratio to the engine and transmission, axles help optimize the vehicle's performance by setting the appropriate road speed.
Additionally, drive axles perform other functions, such as supporting the suspension system, acting as a mounting point for the brake system, and accommodating the wheel hub, brakes, and bearings.
Axle types: Single and tandem axles
Cummins Inc.’s axle and drivetrain business produces various types of axles, including single (solo) axles and tandem axles, each with different key components.
For a single/solo axle, the primary components include:
- Carrier and caps mounting
- Ring gear and drive pinion
- Main differential
- Axle shafts
- Axle housing
A tandem axle consists of both a forward and rear axle. The rear axle is the same as a single axle, while the forward axle includes additional components, such as an interaxle differential assembly, helical gears, and a differential lock shift system.
Tandem axles are particularly important in heavy-duty applications, as they are designed to handle higher loads and provide better traction. Cummins offers various 40,000-pound tandem models to cater to different on-highway and off-highway applications.
How axles help increase efficiency and reduce emissions
Axles play an important role in vehicle emissions by impacting fuel economy. Simply put, better fuel economy means burning less fuel, which directly reduces emissions. The axle's gear ratio sets the vehicle's road speed and determines the engine’s cruising RPM (revolutions per minute). With a lower RPM, the engine uses less fuel, resulting in fewer emissions.
Power loss in the axle can also reduce efficiency and lead to higher emissions. This loss happens due to friction, gear churning, and heat generated during axle operation, causing both speed- and load-dependent inefficiencies. At Cummins, we test our axles for efficiency to measure and minimize power loss, so we can reduce emissions operating costs for our customers.
All axles must comply with EPA regulations and meet Original Equipment Manufacturer (OEM) certifications to ensure they adhere to emission and warranty requirements.
The drive axle has evolved significantly in the recent years specific to efficiency improvements. Specifically, we have employed proprietary Fuel Efficient tapered bearings., primary gearing with reduced frictional losses at the gear mesh., and we have expanded the use of our Patented Lube management system to reduce gear oil churning losses while simultaneously managing axle operating temperatures. These improvements result in an increase in axle efficiency and the overall drivetrain system.
The evolution of drive axles
Drive axles have come a long way. In the 1950s, tandem axles became popular to support heavier loads, and as engines moved from gasoline to diesel, axle gear ratios evolved to keep efficiency high.
Ten years ago, a fast axle ratio was 3.7:1; today, Cummins Drivetrain and Braking Systems (formerly known as Cummins-Meritor) offers ratios as low as 2.15:1, with plans for even faster options like 1.95:1 to improve fuel economy and cut emissions.
Axle ratios are calculated by dividing the number of pinion teeth by gear teeth—a lower ratio enables higher road speed at a given engine RPM, reducing fuel use and emissions. Cummins has also designed axles specifically for down speeding, where engines run at lower RPMs without sacrificing speed. For example, the 14X HE tandem drive axle includes a lube management system, high-efficiency bevel gearing, and fuel-efficient tapered pinion bearings. These features help cut friction and rolling resistance, boosting fuel efficiency.
Looking ahead: The future of axle technology
As the commercial transportation industry evolves, so do the demands on drive axles. Cummins Drivetrain and Braking Systems is leading this change, developing next-generation tandem axles with gear ratios as fast as 1.95:1. These axles are engineered to integrate seamlessly with Cummins engines and Eaton Cummins transmissions.
Cummins is making the industry more sustainable by advancing axle technology and combining it with key components like turbochargers, ECMs, and sensors. Innovations in gear ratios, downspeeding and power-loss reduction are helping customers boost performance and fuel efficiency while reducing emissions.
Cummins is making axles lighter, tougher, and more fuel-efficient. In the 40,000-pound tandem axle market, customers can now choose models built for specific applications, from long-haul trucking to other heavy-duty operations.
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