Axles are among the most crucial components of a vehicle. They are sturdy metal rods or shafts that join the wheels and assist them in rotating in the right direction. Your car would not be able to move without axles. The engine delivers power to the axles, which distribute that power to the wheels, enabling the vehicle to travel forward or backward.
In most cars, axles contribute to movement in addition to providing support to the vehicle and the load that the car might be carrying. In a live-axle suspension system, the axle doubles up – aligning the wheels as well as transferring power from the engine to the wheels. It is used extensively in trucks, SUVs and heavy vehicles.
Specific axles, such as the front beam axle of large buses and trucks, are intended primarily for support and not power transmission. Non-driving axles, however, do not transfer power from the engine; they merely assist in suspension and steering. Most front-wheel drive vehicles have robust rear hubs rather than conventional rear axles because only the front wheels are powered. Recognizing the various axle types and functions is essential for understanding how your vehicle works.
In this post, we will discuss everything you need to know about axles: how they work, the different kinds, and, most importantly, how many axles a car has. Other provisions for discussion will include its replacement timing, cost, and much more. Let’s take a look.
What is an Axle?
An axle is a mechanical element that transmits power from the engine to two opposite wheels, connecting them through a differential. A differential helps the wheels rotate at different speeds, which is very important for making smooth turns, especially on dry or high-friction surfaces.
In many vehicles, the axle is also part of the suspension system to support the car’s weight and keep its wheels aligned. Axle designs vary between vehicles, from solid axles to IRS (Independent rear suspension), affecting handling, performance, and weight distribution. It commonly describes a system of wheels that are in line with one another, although there may be no direct physical element holding them together, such as the front axle of a rear-wheel-drive vehicle.
The term axle is often used in this way in modern toll systems that charge based on the number of axles. It is understood that more axles generally indicate more weight and wear on the road. It is not only helpful for mechanics to understand axles but also drivers, tolling systems, and the auto industry in general.
Types of Axles
When talking about cars, axles are the vital structure that allows anything else to move. Broadly, there are two types of axles found in a car:
- Dead Axle: This type of axle does not operate in connection with the engine and normally supports the vehicle’s weight.
- Live Axle: This axle operates in conjunction with the wheels and transmits power to the wheels from the engine to move the car forward.
These two axles are united through a constant velocity (CV) joint which provides smooth movement while steering and crawling through bumpy terrain.
These aside, axles can be broadly divided into three types:
- Front Axle
- Rear Axle
- Stub Axle
Let us discuss each in detail.
1. Front Axle
The front axle is the axle located in the front of a vehicle and aids in steering. It also absorbs shock loads from bumps and uneven road surfaces, giving a more comfortable ride. Front axles are made from high-strength carbon steel or nickel steel, which gives them durability and resiliency to meet extremely difficult driving conditions. A sturdy front axle is specially for off-roading or driving on rugged terrain.
A front axle consists of four major components:
- Beam: The main structural part of the axle.
- Swivel Pin: Connects the stub axle to the beam, to allow controlled movement.
- Track Rod: Prevents mechanical damage by keeping the alignment and steering response intact.
- Stub Axle: It carries the wheel assembly and facilitates free rotation.
Depending on the design of the vehicle, there can be two types of front axles:
- Dead Axle: Carries the load weight of the vehicle but does not deliver power.
- Live Axle: Transfers power into the wheels, which help in propelling the vehicle forward.
2. Rear Axle
As the name itself indicates about the rear part, the rear axle is placed at the end of the vehicle and is basically used to transmit power from the differential to the wheels so that the car can move. The majority of rear axles are live axles, i.e., they actively contribute to propulsion.
Rear axles are divided into two halves, known as half shafts, and are linked by the differential of the car. The differential enables the wheels to turn at various speeds, something that is very essential while turning.
Three principal types of rear axles exist:
- Semi-floating axle: Typically used in cars, SUVs, durable mountain vehicles, mid-sized trucks. It is attached to the wheel and a flange on the outside of the axle shaft. Two bearings are used in this design—one to bear the axle shaft and the other attached to the axle casing.
- Full-Floating Axle: In heavy-duty trucks, this type of axle utilizes two bearings and can “float” in its position while conveying torque. More stable, it is suitable for trucks carrying heavier loads or used on rough ground.
- Three-Quarter Floating Axle: Providing better stability compared to a semi-floating axle yet still keeping wheels aligned, it is more sophisticated but offers smoother travel and reliability.
3. Stub Axle
The stub axle is smaller than the others and is seen on rear-wheel drive vehicles, with its fittings visible on the front wheels. The front axle is connected via a kingpin through which the front wheel is allowed to rotate when steering.
The following are the four types of stub axles:
- Elliot Stub Axle: Joined to the front axle via a kingpin, cotter, or yoke type.
- Reverse Elliot Stub Axle: The same as Elliot but inverted.
- Lamoine Stub Axle: This axle uses an L-shaped spindle rather than a yoke and offers a different structural approach.
- Lamoine Reverse Stub Axle: Reverse designed Lamoine Stub, offers a different setup.
How Many Axles Does a Car Have?
The number of axles in a vehicle is determined by its size, design, and purpose. The majority of standard vehicles have two axles, with one in the front and one in the rear. Axles hold the weight of the vehicle and allow the wheels to rotate smoothly, which enables the car to move correctly on the road. More oversized vehicles, like trucks, buses, or even some family-friendly SUVs, could operate with three or more axles. Additional axles increase load-bearing capacity and provide a sense of stability during operations. Depending on how the vehicle is designed, these axles can either be evenly or unevenly distributed across the chassis.
In the majority of automobiles, the front axle and the rear axle are the two main axles. The front axle plays a vital role in the steering of the vehicle by controlling the movement of the front wheels. The rear axle operates with the drive axle and is responsible for the power transfer from the engine to the wheels to propel the vehicle forward or backward.
The amount of axles can also contribute to the turning radius of a vehicle. Longer vehicles like semi-trucks and buses tend to require more space to perform turns, a defining characteristic of their longer wheelbase. This explains why large commercial vehicles have a much wider turning radius than regular cars.
More significant numbers of axles in a vehicle result in a larger turning radius. These vehicles with a more substantial axle number, such as buses and semi-trucks, therefore require more space to turn because of their considerable wheelbase. This is why more oversized commercial vehicles have a wider turning radius than passenger cars.
In general, axles are central to any vehicle and play a vital role in weight distribution and movement stability. The adequate number of axles ensures ride comfort while still meeting the driving and safety requirements.
How Does an Axle Work?
When you start the car, the ignition starts the engine, which then begins the spinning of the crankshaft and provides the torque. The crankshaft is responsible for transmitting this power into the drivetrain system via the coupling to several accessories. One of the components of that system is the axle.The axle acts as an interface between the engine and the wheels as it transmits rotational energy from the former to the latter, making the car move.
However, the axle is not just a simple link; between it and the wheels is a series of mechanical elements starting from the transmission that, in some way, help control the percentage of power passing through. So, the axle connects your engine to your wheels. Without it, your car would go nowhere.
Which Type of Axle Does My Car Have?
There are various types of axles fitted to broad types of cars, and an understanding of their type will help you anticipate performance, maintenance, and costs for repairs. An axle’s configurations depend on whether your car is front-wheel drive, rear-wheel drive, or four-wheel drive. Whether you own a vintage luxury sports car or a plug-in hybrid SUV, knowing the type of axle is very important.
Some have solid axles, while others have independent axles for better handling. The type of axle may affect weight, power distribution, and the stability of the entire auto. If you wonder what kind of axle exists in your car and how the axle affects your drive, let’s get into it in simplified terms.
- Sedan: Most of the sedans have been designed around the front axle. This is because sedans were built to provide comfort, excellent fuel efficiency, and smooth riding stress that originates from the front axle alone. The rear wheels follow the movement of the front wheels, ensuring ease while driving.
- SUVs: Though SUVs are a class of vehicles generally built with a rear axle design that enables weight balance and stability, this is given to better handling, mostly in rough road conditions. How many axles does an SUV have? Just know that, for some SUVs, this might go beyond two axles, depending on the weight of the SUVs naturally.
- Trucks: If you own a truck, it might likely have rear axles or a four-wheel driving axle design. Because they are built to carry heavy loads, trucks require full-floating axles. This design makes towing stable with a cargo weight on rough terrain.
- All-Terrain Vehicles: All-terrain vehicles and four cycles have specialized axle setups to conquer muddy roads, bumpy trails, and rocky outlying routes. In most configurations, two axles transmit torque to all of the four wheels to create traction and power distribution. According to the weight and overall vehicle setup, the design of the axle varies.
- Electric Vehicles: Electric vehicles have changed the axle game for good. Instead of traditional axles, many electric cars such as the latest Tesla Models have also adopted one based on electric hatchbacks, called E-Axles. The setup has all parts incorporated into a single unit: a gearbox, motor, and inverter—all in much less space than in a regular engine.
When Should You Replace Your Car’s Axle?
In today’s front-wheel-drive vehicles, CV axles (otherwise referred to as half-shafts) are responsible for transferring engine power to the wheels. With the spinning of the axles by the engine, the wheels rotate, which makes your vehicle move forward. The axles also consist of a sophisticated joint that provides smooth power transmission even when your front wheels turn or change direction over road bumps.
But as with any other car component, CV axles deteriorate over time—and when they do, they can get you into real trouble. Below are some indicators that show you have some axle issues and it’s high time to change your car’s axle before you get stranded.
1. Your Car Will Not Move
If your CV axle fails entirely, your vehicle won’t budge whatsoever. This will usually happen because of excessive damage, such as an accident that breaks the axle or the universal joint coming loose. In such a scenario, your best course of action would be to have it towed and the axle replaced ASAP.
2. Grease on the Inside Edge of Your Front Tires
Grease on your front tires is one of the first symptoms of axle problems. The CV axle joint is filled with lubricating grease and protected by a rubber boot. Eventually, this boot cracks or tears and lets grease out. When it does, you may notice a greasy, sticky residue on the inside rim of your front tires.
If you see this, pick up a flashlight and inspect under your vehicle closer. A leaking CV axle boot exposes the joint to dirt and moisture, and further damage is sure to happen if it’s not repaired in the near future.
3. Clicking Sound When Turning
The sound of a click upon turning sharp corners is an unmistakable warning that your axle is at the end of its life. When all the grease has leaked out, the metal components within the joint will wear against one another and emit a staccato-clicking sound that worsens when you accelerate or turn the wheel.
Please don’t ignore this warning, as it can result in total axle failure. If you hear clicking upon turning, have your CV axle inspected immediately.
How Much Axle Replacement Costs?
In general, replacing one axle can cost around $300-1,500, based on your car and the duration of the job. The parts themselves usually cost you around $760 and $1,030, while labor adds another $170 to $180.
Typically, replacing one axle takes about 1.5-3 hours. This requires more time, about 12 hours, and all four axles are being replaced, which naturally increases the cost of purchasing the axles as well as paying for labor. No need to panic. Fortunately, you don’t have to upgrade all four at once. In most cases, replacing just one is enough.
Here are a few things that greatly influence the cost:
- Vehicle Category: The car you drive makes a difference. Bigger cars and trucks generally require higher repairs since they have more significant parts and demand more time. However, the newer ones are meant to go for longer before needing a car maintenance service.
- Axle Types: Not all axles are the same. Some are more complex, especially if they have things like limited-slip differentials or electronic parts. These cost more because they need special tools and parts.
- Labor Costs: Labor costs may vary according to different places of residence as well as the mechanic’s experience. Some areas will charge a higher rate than others.
- OEM vs. Aftermarket Parts: When it comes to parts, you can choose between OEM (original equipment manufacturer) or aftermarket parts. OEM parts tend to be pricier, as they are manufactured especially for your car, while aftermarket parts are not always an exact copy, but they come less expensive.
Relevant FAQs
Do SUVs and sedans differ in axle configuration?
No, they typically feature the same axle configuration: two axles, one in the front and one in the back. There are, however, much larger size and design differences between these vehicles; in axle configuration, they remain essentially the same, no matter whether it is a compact sedan or a huge SUV.
How do axles affect the handling and efficiency of a car?
Axles play a significant role in the handling and performance of one’s car. While supporting its weight, they also deliver power to the wheels. A suitable axle setup enhances turning smoothness, better stability, and complete control. Indeed, even the type of axle—solid or independent—also impacts ride quality and how responsive a car is on the road.
Do axles impact the towing capacity of a vehicle?
Yes, The more axles, the more towing power it tends to get because the extra axles will help disperse the weight better, relieving the frame of some of its stress. Trucks and trailers with more axles can, therefore, haul heavy loads more safely and prove particularly useful when pulling recreational boats, campers, or anything needing that extra bit of support.
What are the signs that your car has developed a lousy axle?
Car axle problems can be hazardous, but there are a number of warning signs. When a car refuses to move forward even with the engine running fine, you should be alarmed. Some of the other signs include heavy acceleration, clunking or sputtering noise, vibrating or wobbling ride, possible failure with both brakes or some oil leakage just near the axle. Once you notice any of these signs, please don’t delay any further when you want to try to fix it; deal with it quickly before it worsens.
In conclusion, when talking about how many axles a car can have, it goes beyond just mechanics—this knowledge will be helpful in everyday driving, maintenance, and even choosing the right vehicle for your needs. While cars typically have two axles, larger trucks, SUVs, and performance vehicles will likely have more axles.
If you’re curious about how axles affect handling, towing, or repairs, this knowledge will help inform better vehicle usage decisions. So, the next time you drive, you’ll know what’s going on under your vehicle.
