What Is Axle?- Definition, Uses | Types of Axles

An axle is a rod or shaft that rotates the wheels and supports the weight of your vehicle. Axles are essential components of any vehicle and come in three main types: front, rear, and stub.

Let’s break down the types of axles and look at how to choose the right axle ratio for your vehicle.

What is an Axle?

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle.

In the former case, bearings or bushings are provided at the mounting points where the axle is supported.

In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type of axle is referred to as a spindle.

Factors That Decide the Type of Axle in a Car

Several factors determine which type of axle a vehicle needs. For example, the technical requirements and the force generated play a major role in the decision on the type of axis.

Some vehicles have pre-built axles in standard formats. Others have bespoke axles that meet the needs and specifications of the car.

Custom axles are best for cars as they allow more individual control over the wheels. These axles can fine-tune the speed and torque of the wheels.

Types of Axles

There are typically three types of axles – the rear, front and stub axle.

#1. Front axle.

Located in the front of the vehicle, this axle is responsible for assisting with steering and processing shocks from the uneven surface of the road. They have four main parts, which are the beam, the swivel pin, the track rod, and the stub axle.

Front axles must be as sturdy as possible, and that’s why they’re usually made from carbon steel or nickel steel.

For the front axles on vehicles, they can either be a live front axle or a dead front axle.

• Live Front Axle: As mentioned before, these axles deliver power to the wheels. These types of axles are commonly used in Front Wheel Drive (FWD) cars, Four Wheel Drive (4WD) cars and All-Wheel Drive (AWD) vehicles.
• Dead Front Axle: These are used to support the weight of the vehicle and also do not actively spin the wheels. Most dead front axles and differentials have housings that prevent them from coming into contact with water or dirt.

#2. Rear Axle.

Similar to the front axle, rear axles also can be either live axles or dead axles. For example, a front-wheel drive vehicle will have a dead rear axle.

Also, rear-wheel drive and all-wheel drive will have live rear axles. This axle is responsible for delivering power to the driving wheels.

It comes in two halves, known as half shafts, which are connected by the differential. In most cases, rear axles are live, meaning they rotate with the vehicle’s wheels.

There are a few types of rear axles on vehicles. These include Semi Floating Axles, Full Floating Axles, and Three-Quarter Floating Axles. These axles differ based on what support the vehicle needs and where the axle is mounted.

Types of Rear Axles:

Full Floating Axle: These types of axles do not support the weight of the vehicle, instead they are used to just send power to the rear wheels through the differential. The weight is instead supported by the spindle that is attached to the axle housing. Also, the wheel hub is attached to this spindle.

These types of axles are commonly used on heavy-duty trucks. This is because the axle’s load capacity is larger. Also, because of how the wheels are mounted, an axle shaft can be removed if damaged while the wheel is still able to spin unpowered.

Semi-Floating Axle: Compared to the full floating axle, the semi-floating axle partially supports the weight of the vehicle while also being used to transmit power to the wheels. The wheel housing connects to the axle through a bolted flange. This type of axle is popular on light or medium-weight 4WD trucks and cars.

Three-Quarter Floating Axle: The three-quarter floating is a combination of the semi-floating axle and the full floating axle. Instead of the axle supporting the weight of the vehicle, the bearings on the wheels are attached to the axle casing and hub. The weight of the vehicle is then moved to the axle casing rather than the axle.

Also, this removes any shearing stress from the axle but other loads such as bending loads affect the axle. This type of axle is also used on lighter trucks and cars but is not as popular as the cheaper semi-floating axle.

#3. Stub Axle.

The stub axle, also known as a stud axle, is a car axle that attaches to one wheel. These can be used in vehicles such as front or rear-wheel drive vehicles to support the wheels that do not have power going to them.

For example, the rear wheels in a front-wheel drive vehicle may be supported by stub axles. Additionally, these axles have a wheel bearing that supports the wheel hub. These types of car axles also attach to an axle through a kingpin.

If you didn’t know, a kingpin is a large bolt that is used as a pivot. And, the cotter is a pin or wedge that goes through a hole in the kingpin to connect it to the axle. It makes sure the kingpin does not come out of the connection between the stub axle and the other axle.

There are four main types of stub axles.

Types of Stub Axles

• Elliot: An Elliot stub axle connects to the axle by fitting inside the yoke of the main axle. Then, the stub axle is connected through the yoke by a kingpin and a cotter.
• Reverse Elliot: For the Reverse Elliot stub axle, the stub axle has the yoke and fits around the main axle. The Reverse Elliot stub axle then connects the two axles with a kingpin and a cotter
• Lamoine: This axle uses an L-shaped spindle that connects to the axle with a kingpin and cotter. The cotter also locks the axle in position. This is a common stub axle on tractors and other heavy vehicles.
• Reverse Lamoine: As the Lamoine stub axle forms an L-shaped spindle, the Reverse Lamoine forms an inverted L shape. It connects in a similar to the Lamoine stub axle with a kingpin and a cotter.

How many axles does a car have?

Generally, a vehicle will have one axle for every two wheels it has. The axle connects one wheel on one side to another wheel on the other side. And because cars have four wheels, they have two axles.

As you might expect, larger vehicles sometimes have more axles. There might be an extra axle in a large pickup truck, for example.

How to Know When Your Axle Is in Disrepair

Because axles are essential to your car’s operation, it’s important to keep them working properly. if you see one of the following signs, you can tell that your axle is in disrepair:

• You hear a loud clunk when you put your car into gear.
• You feel vibrations when you operate your car.
• Your vehicle won’t move forward or backward even though it’s running.

Why Should You Inspect Your Axles?

Regular axle inspection is an important part of car maintenance because spotting trouble early on can help you avoid expensive repairs in the future. The cost of axle repair can increase drastically if you have to replace any of the axles.

What To Look for When Inspecting

Most car mechanics will inspect your axles whenever you bring in your car – but you can also conduct an inspection yourself. You won’t need any tools to do it, but you will need to get underneath your vehicle.

Depending on how low your car is, you might need something to lift it up off the ground. You can use carjacks or vehicle ramps to do this.

Visual Inspection

The easiest part of the inspection is taking a close look at the boot, which is responsible for keeping joints lubricated and preventing dirt and water from getting in. They explain that the boot has ribs in it to allow it to flex and move with the vehicle.

Check for holes, splits, or grease that is leaking. Next, you should inspect the shaft for any nicks, dings, or dents, as well as if there are signs that anything is rubbing on it.

You also need to check the clamps that connect the boots to the shaft to ensure there are no leaks.

Driving Inspection

You can also take a test drive to determine if there is anything wrong with your axles. If you notice any of the following signs, your axle might be in disrepair:

• When you put your car into gear, there is a loud “clunk” sound.
• Your car vibrates when you operate it.
• There is a clicking or popping noise when you turn your car.
• Your car is running, but it won’t move forward or backward.

Top 6 Signs of a Damaged or Broken Car Axle

When a car axle breaks, either abruptly (like hitting a curb) or due to frequent overuse (like driving with too much payload), you’ll usually know there’s a problem because the tires simply won’t spin.

However, there are some signs and symptoms of axle damage that might indicate a broken axle—and a visit to an axle repair shop is on the horizon.

#1. Car Won’t Budge.

The most obvious sign of a broken axle is when your car tires won’t rotate. The car will turn on fine. Its engine will sound happy as a clam when you rev it. There aren’t any electrical issues—no dashboard warning lights, no weird clicking sounds. It. Just. Won’t. Move.

Why does this occur? It’s usually the result of a bent axle joint that’s finally snapped like a Slim Jim. You’ll need a tow truck to haul it to a repair shop near you for an inspection and axle damage repair.

#2. Vehicle Strains.

Car axles are fairly resilient, but when they’re under pressure, you’ll feel it in the gas pedal. When an axle is bent or damaged, your vehicle might begin to strain.

You’ll put it into gear and notice right away that power isn’t getting transferred to the wheels (i.e., it’s slow to get going).

A straining vehicle doesn’t necessarily mean that you have a bad car axle, however. This should accompany some other signs of axle damage (below).

#3. “Sputtering” Noises.

Along with straining to move, the vehicle may also make sputtering, bumping or clunking sounds. This is because the axle is not able to transfer adequate power to the wheels.

These bad axle sounds will be audible when the car begins to move as well as when turning the wheels.

#4. Wheel Wobbling & Vibrations.

Underinflated tires, unaligned wheels and loose lug nuts can also make your vehicle vibrate.

But if you notice any other signs of axle damage, don’t disregard it! Your car is incredibly dangerous to drive once you begin noticing vibrations caused by a damaged axle or other suspension problems.

#5. Brake Pad Misalignment.

You’ll notice some braking issues once your bent axle starts going bad. The brake pads will begin to shift and become misaligned with the wheels and rotors, and once that happens, you may notice the vehicle skids or slips to a stop.

Over time, the brakes will eventually cease to function at all.

#6. Leaking.

The brake seal on an AWD or 4WD vehicle’s driveshaft may shift and begin to leak small amounts of oil. This will be noticeable when looking at the brake drum.

Axle CV joints can also leak grease, which is not as detectable. However, once this happens, the joints will collect dirt dry out, and deteriorate quickly.

How Do I Know When To Replace The Axles?

The great thing about axles is that they are durable and thus incur damage only when extreme force has been applied. But if you start having problems, they do show common symptoms. These are:

• Car vibrations. If you went over an especially challenging pothole, unexpected curb, or other such objects, you might have caused your axle to get damaged. If you did, then you’ll experience vibrations along with a rumbling sound underneath the vehicle or even tire wobbling. These will be noticeable during accelerations, decelerations, or turns.
• Loud clanking, clicking, or clunking. The axle was damaged if you hear loud clanking or clunking as you put your vehicle into gear or the car struggles to get power to move.
• Grease leak. If there’s a puddle of grease underneath your auto or inside the tire edge, this is a sure sign of trouble. Even though the axle may not be damaged just yet, an insufficient amount of grease may cause further problems.
• Your vehicle doesn’t move. If your engine is revving, but the vehicle doesn’t move an inch, the axle joint was damaged, and you need to service the car.

How Much Does It Cost To Replace One?

Because there’s a lot to take in when dealing with axles, it’s best to leave the repairs to a qualified mechanic. What’s more, it’s even better not to drive to the auto shop and call a tow truck just in case something else happens with the vehicle.

After some diagnosing, the mechanic will explain the problem and give you the price. Here, everything depends on what exactly happened.

On average, replacing one is around $880, and $959 for an axle shaft. Repairing a front axle is about $550-$740, with the rear one approaching $480-$550.

Luckily you won’t have to do this often, and the replacement should last you for a while. However, it’s highly advisable to service your car when you notice any of the symptoms.

Are Car Axles Covered by Insurance?

If your car axle is damaged or broken as a result of an accident or hazard, it may be covered by your car insurance (depending on your specific policy). Damage from wear and tear or aging is not covered by car insurance.

It is possible to buy warranty coverage for major components, such as the engine and transmission, but this is separate from insurance and subject to its own set of rules and restrictions.

FAQs.