Which Axle Is the Drive Axle on a Semi-truck?

A semi-truck has two axles: the drive axle and the steer axle. The drive axle provides power to the wheels, while the steer axle enables the truck to turn. As the drive axle is closer to the truck’s cab, it typically bears more weight than the steer axle, providing traction when carrying a heavy load. The steer axle is positioned at the front of the truck, and its wheel is part of the steering mechanism, allowing the wheel to determine the direction in which the truck turns.


Which Wheels Drive on a Semi?

Contrary to popular belief, not all semi-trucks have four-wheel drive. Most semis have a tandem axle configuration, in which only the rear wheels are driven. This is because four-wheel-drive trucks are more costly to buy and maintain than tandem axle trucks, which are less fuel-efficient and shorter-lived. Tandem axle trucks are, therefore, the favored option for most trucking companies. However, some situations require a four-wheel-drive truck, such as traversing rough terrain or carrying heavy loads. Ultimately, the truck choice depends on the trucking company’s specific needs and the loads it will be hauling.

How Many Drive Axles Does a Semi Have?

A semi-truck has three axles: the front steering axle and two drive axles located under the trailer that power the truck. Each axle has its set of wheels, which the engine powers through a driveshaft. This configuration distributes the truck and trailer’s weight evenly, making it more maneuverable and helping to prevent tire wear and tear. Moreover, it provides excellent stability when carrying heavy loads. Occasionally, a fourth axle is added for additional support, but this is not always necessary. The number of axles on a semi-truck depends on the load’s size and weight.

How Does the Drive Axle Differ From the Dead Axle?

The drive axle is the axle that receives power from the engine to turn the wheels. In contrast, the dead axle does not receive power from the engine and is not used to drive the vehicle. Dead axles, which do not rotate, typically support the car’s weight and serve as a place to mount the brakes and suspension components. Sometimes, a vehicle has both a drive axle and a dead axle. For example, a semi-truck typically has a front-drive axle and two rear dead axles. This configuration distributes the cargo weight more evenly.

Is Drive Axle Part of Suspension?

The drive axle is a suspension part that links the wheels to the drivetrain, which transfers power from the engine to the wheels. Although typically situated in the vehicle’s rear, the drive axle can also be in the front. It consists of two parts: the shaft and the differential. The differential distributes power evenly to both wheels, allowing them to rotate at different speeds, making turning possible. While both wheels must rotate at the same speed for a vehicle to move forward, the differential lets each wheel rotate at a different speed when the vehicle turns.

Is CV Axle Same as Drive Shaft?

While their names may sound similar, a CV axle differs from a drive shaft. The CV axle is a component of a car’s suspension system, and its purpose is to transfer power from the engine to the wheels. In contrast, a drive shaft is part of the transmission system and delivers power from the engine to the differential. Although they serve different functions, the CV axle and drive shaft are necessary for a car to function correctly.


Determining the drive axle on a semi-truck is crucial for several reasons. The drive axle powers the truck, contributes to weight distribution, and connects the wheels to the drivetrain as part of the suspension system. Understanding which axle is the drive axle can enhance your comprehension of your vehicle’s functioning and prove beneficial if you need to replace any parts.

About the author, Laurence Perkins

Laurence Perkins is the passionate car enthusiast behind the blog My Auto Machine. With over a decade of experience in the automotive industry, Perkins has knowledge and experience with a wide range of car makes and models. His particular interests lie in performance and modification, and his blog covers these topics in-depth. In addition to his own blog, Perkins is a respected voice in the automotive community and writes for various automotive publications. His insights and opinions on cars are highly sought-after.