Getting To Know Your Driveline: Axles

How Axles Help Move Your Semi-Truck

If you've been following our series on the driveline in your semi-truck, then it's likely you have some questions about axles. While they may seem like an overlooked component in your driveline, axles actually serve several important purposes. In this article we'll be discussing how axles help move your commercial truck. Read on to learn more about axles!

What Is A Semi-Truck Axle?

A drive axle provides motive power and propels the truck forwards or backwards. It is connected to the engine via the differential, driveshaft, and gearbox. A truck can have more than one drive axle, but it's not always possible to tell how many drive axles a truck has, or which ones they are. The more heavy-duty the requirements are for a truck, the more likely it is to have two drive axles.

How Many Axles Are On A Semi-Truck?

The tractor unit is commonly made with two or three axles. Trucks designed to move heavy-duty commercial loads can have as many as five, some often being lift axles. The most common tractor-cab configuration has a forward engine, a steering axle, and two drive axles.

What Is A Three-Axle Semi-Truck?

The definition of a tri-axle vehicle includes a truck, tractor, or trailer with three axles that are grouped together at the rear end of the vehicle. Tri-axle vehicles are most used with hauling heavy loads. Multiple axles and wheels provide improved weight displacement and enhanced stability over trucks with less axles.

Semi-Floating vs. Full-Floating Axles

There are two kinds of axles available when you are choosing which kind of driveline is best for your needs. These are semi-floating and full-floating axle configurations. There are several differences to look out for when you are choosing specifications for your truck.

Semi Floating Axle

A semi floating axle is designed to use a one-piece wheel hub that is directly connected to the axle shaft. This is supported by a bearing that is placed near the wheel end of the axle tube. The weight of the truck and any cargo will be carried by the axle shaft itself.

Full Floating Axle

A full floating axle is made using a wheel hub system that is a separate piece from the axle shaft. The full floating system uses a spindle bolted to the axle tube that supports the wheel hub by with a set of wheel bearings. In this case, the weight of the truck and cargo is transferred to the axle tube, instead of the axle shaft.

What Makes Up A Semi-Truck Axle?

There are several components that make up your axle system each of which is designed to make sure your truck moves smoothly. Components of an axle include:

1. Stub Axle

2. Seals

3. Cross Shaft

4. Pinion Gears

5. Input Yoke

6. Side Gears Profile

7. Helical Drive Gear

What Is A Drive Axle?

A front drive axle is designed to utilize the power that is transmitted from the transfer case via the drive shaft.

Universal joints, located on the outer ends of the axles, let the front wheels and hubs move while still transferring power. UV joints are included to make sure the front wheels on a front drive axle turn on the axle spindle arm by the axle shaft itself.

Vehicles that utilize a four-wheel drive axle require locking hubs for the front drive axle to function properly — locking hubs transfer power from the driving axles to the driving wheels on four-wheel-drive systems.

Read More About Drivelines

If you have been researching drivelines and would like to know more about some of the individual components that make up the system, we have several articles designed to help you do exactly that. Click on any of the links below to read more about each part!

· Getting To Know Your Driveline­

· Getting To Know Your Driveline: Clutches

· Getting To Know Your Driveline: Yokes

· Getting To Know Your Driveline: Driveshaft

· Getting To Know Your Driveline: U-Joints

· Getting To Know Your Driveline: Differentials

Shop Now For Semi-Truck Driveline Parts

For those looking into replacement parts for their semi-truck, you've definitely found yourself at the right location. No matter what driveline part you've been needing for your semi-truck, we have a full selection for you to choose from. Whether you are looking for clutches, axles, yokes, driveshafts, universal joints, or differentials, we'll have it from some of the most notable brands in the industry. Login or create an account to start saving on your next driveline component today!