Every time a technical term is used, there is a lot of misunderstanding among people. Now, the definition of an axle is relatively simple. So, what does it mean exactly when you hear of a 2-axle, 3-axle, or 4-axle vehicle?
An axle is where the wheels are connected on either side. The number of axles a vehicle has will determine the maximum number of wheels used. A vehicle with two axles can have three, four, or six wheels. Vehicles with three axles can have six to ten wheels, while those with four can have eight to fourteen wheels. Most cars have two axles. Cars and trucks have one axle for every pair of wheels. These are known as “2-axle” cars, which most of you see on the road today. Motorcycles have two axles as well.
Read on to learn more about a 2-axle, 3-axle, or 4-axle vehicle and how many axles a car or truck can have.
What Is a 2-Axle, 3-Axle, and 4-Axle Vehicle?
You can think of an axle as a central shaft for a revolving wheel or gear in a vehicle. In other words, it is the major structural component to which the wheels are fastened and which runs the length of the vehicle. The number of wheels on a vehicle depends on the number of axles.
What Is a 2-Axle Vehicle?
It is a type of vehicle that has three or four wheels. Most cars, SUVs, and pickup trucks are the 2-axle type of vehicle.
What Is a 3-Axle Vehicle?
3-axle vehicles can have six to ten wheels. An example of a 3-axle vehicle is a tractor-trailer, also referred to as a semi-truck or an 18-wheeler.
What Is a 4-Axle Vehicle?
Although they are less common, 4-axle vehicles exist today and can have up to 14 wheels. Garbage trucks are an example of a 4-axle type of vehicle.
What Is the Main Role of an Axle?
Support the Vehicle’s Weight
Its main function is to support your vehicle’s and its cargo’s weight. The number of axles will certainly increase with weight, as illustrated in the FHWA vehicle classification. That is why semi-trucks and garbage trucks feature many axles due to the necessity to sustain a large amount of weight.
Transmit Power from the Engine to the Wheels
Another function of the axle is to transmit power from the engine to the wheels. A gearbox called the differential contains several gears that the axle uses.
The differential enables each wheel to spin at a separate speed. This is important since the outside wheels of a turning vehicle must go a longer distance than the inside wheels.
Impacts a Vehicle’s Mobility
The number of axles can also have a big impact on the mobility of the vehicle. For example, garbage trucks need to be able to make sharp bends to get into narrow locations, which is why they have four axles.
How Many Axles Does a Car Have?
Cars Typically Have Two Axles
Cars typically have two axles, which rotate the wheels. A larger car with more wheels and passengers may have more axles.
Check Your Car’s Side
Finding out how many axles your car has is simple. All you need to do is take a side view of your car and count the number of pairs of tires. Most cars have two sets of tires, one in the front and one in the back, for four tires. Two axles are equal to two pairs of tires.
What Determines the Type of Axle in a Car?
What kind of axle a car needs depends on several things. For instance, choosing the right axle depends greatly on the technical specifications and the amount of force generated in your car.
Axles in certain cars are pre-made and come in conventional sizes. Others have axles specially made to meet the demands and requirements of the vehicle.
Since they give the user more precise control over the wheels, customized axles function best for cars. These axles have a finer range of adjustment for the torque and speed of the wheels.
Types of Axles
There are three main types of axles:
1. Rear Axle
This type of axle delivers a lot of power for the driving wheels. Its two parts are the half shafts joined together by the differential. Generally speaking, the rear axles spin along with the vehicle’s wheels.
2. Front Axle
This axle helps to steer and absorbs shocks from the road’s irregular surface. The front axle’s four primary parts are the beam, swivel pin, track rod, and stub axle.
Front axles must be as strong as possible, often made of nickel or carbon steel.
3. Stub Axle
The stub axle is an axle that only supports one wheel and is carried at its other end by the vehicle’s chassis or another object. This type of axle is where the road wheel mounts. You use kingpins to join the front axle to the stub axle.
Essentially, these stub axles revolve around a kingpin, a small drive fitted into the eye of the axle beam and secured by a taper cotter pin.
Types of Rear Axle
The types of rear axles vary depending on the support and mounting techniques used. There are three different kinds of rear axles:
1. Semi-Floating Rear Axle
This axle securely fastens the wheel to the flange outside the axle shaft. A semi-floating axle must be large since it has two bearings to deliver the same torque. The axle shaft is supported by one bearing, while the other is located inside the axle casing.
Semi-floating axles are used in cars, sport utility vehicles, and mid-size trucks such as light-duty and half-ton pickups.
2. Full-Floating Axle
This axle type actually “floats” in place and retains its position, living up to its name, thanks to two bearings. It is only intended to transfer driving torque. Full-floating axles are often better for larger vehicles like heavy-duty trucks.
Full-floating axles can also be useful for mid-size trucks with higher towing capabilities or those that often use four-wheel drive.
3. Three-Quarter Floating Axle
In addition to being more reliable, this type of axle is more sophisticated than a semi-floating axle. It not only manages side thrust and driving torque but also helps in maintaining wheel alignment.
Types of Front Axles
These are the two different types of front axles:
1. Dead Front Axle
These front axles don’t rotate with the wheels. They remain stationary. Most dead front axles and differentials have coverings that keep them out of the mud or water.
2. Live Front Axle
Unlike dead front axles, which transfer power from the gearbox to the front wheels, live front axles do the opposite.
Types of Stub Axles
There are four different kinds of stub axles:
This axle consists of a kingpin, a yoke, and a cotter.
2. Reverse Elliott
This one features a reverse configuration.
Instead of a yoke-style hinge, this stub axle has an L-shaped spindle.
4. Reverse Lamoine
Its design is the polar opposite of a typical Lamoine stub axle.
Things to Consider When Choosing Your Car’s Axle Ratio
- You can find the fuel efficiency information for the standard axle ratio on the window sticker of your car.
- The fuel efficiency is automatically reduced if the truck has a specific axle ratio option.
- You cannot compare the optional axle ratios from various automakers.
- Lower axle ratios are sometimes referred to as tall gears, and higher axle ratios as short gears by dealers. While the latter can transport bigger loads, the former typically gets superior gas mileage.
Again, what are 2-axle, 3-axle, and 4-axle vehicles? An axle connects the wheels. It determines the number of wheels allowed. A 2-axle car can have three, four, or six wheels, a 3-axle vehicle can have six to ten wheels, and a 4-axle vehicle can have eight to fourteen wheels.
How to Choose the Right Axle Ratio for a Pickup Truck
Many vehicles have custom axle ratios and unique torque, motor, and transmission specifications. According to Edmunds, a drive shaft revolves 3.55 times for every time a wheel turns once when the axle ratio is 3.55:1.
Regular Axle Ratios for Vehicles That Do Not Haul Heavy Loads
A regular axle ratio usually works well for drivers who do not expect to haul heavy loads. However, you would want the largest axle ratio possible if you tow hefty trailers or move enormous weights.
How to Know If Your Axle Needs Repair
Maintaining your axles’ appropriate functionality is important because they are necessary for your vehicle to function well. The axle is prone to wear and tear since its role is demanding. You can know that your axle needs repair if you see one of the following symptoms:
- You experience vibrations when you drive your car
- When you shift into “drive,” your car makes a loud clank
- Misaligned wheels
- The universal joints of the car may also have a crack
If you experience these symptoms, it’s time to take your vehicle to a technician. They will advise you if a full repair or part replacement is needed.
Axle Replacement Cost
Generally speaking, rear axles are not that expensive since they are made of metal, with replacement costs as low as $150.
You can save potential high repair costs by getting regular checkups.
How Many Axles Does a Truck Have?
Trucks with 18 driving wheels sometimes have two tandem axles and one axle beneath the front bumper of the trailer.
Two axles are connected in a straight line. A tandem axle is a configuration in which one axle follows another instantly. Thanks to this, the load weight is uniformly distributed between the two axles. The loader will be able to maintain the load within the permitted limits.
There usually are ten forward gears on an 18-wheeler, along with two reverse gears. This design is the most popular despite anything from nine to thirteen to fifteen or even eighteen gears.
Drivers of 18-wheelers use a “double-clutch” when changing gears. Driving a truck is entirely different from operating a vehicle with a traditional gearbox.
When a semi-truck is fully loaded with a trailer, it has five axles overall. In the strictest sense, a semi-truck without a trailer will have three axles.
Some pickup trucks have additional axles, depending on their hauling. Some have so-called drop axles, which are only lowered when required to support the extra weight.
As we laid out earlier, a typical vehicle always has two axles because they have two wheels, even if they are just standard straight trucks.
On the other hand, a truck towing a tow dolly or a front-wheel-drive vehicle will also have more axles.
A straight truck will have four axles when towing a car trailer but only three axles when towing a tow dolly. Those with two axles have a front and a back axle. They are often small such as light trucks.
Trucks with three axles have a front and two rear axles in place. These are often larger trucks and lighter semi-trailers (tractor-trailer combinations).
Heavy Rigid Trucks
Heavy rigid trucks with four axles have either two driven rear axles or two front axles that are both steerable.
Additionally, large semi-trailers with one front axle and three rear axles exist. You can see this on large vehicles that tow huge loads.
6 Symptoms of a Broken Or Damaged Axle
The tires typically will not spin when an axle breaks, whether suddenly (from striking a curb) or repeatedly (carrying too much freight).
In any case, you will usually notice there is a problem since the wheels will not move. The following signs may indicate a damaged axle or point to a fractured one:
1. Car Not Moving
When your car’s tires do not spin, it is the most evident indicator of a broken axle. It will be easy to start the car. When you rev the engine, it will sound as content as a clam.
Moreover, you are certainly not going to experience any electrical problems. There will be no strange clicking sounds or dashboard warning lights. Nothing. The car will not move.
This usually happens because of a bent axle joint that snapped like a Slim Jim. Remember that you will need a tow truck to transport it to a nearby repair facility for an examination and axle damage repair.
2. Strains on the Car
Although car axles are fairly durable, you may feel some strain on them when pressing the gas pedal. Your car will start to struggle when you have a damaged axle.
When you shift it into “drive,” you will immediately notice that the power is not being transferred to the wheels (i.e., it moves slowly out of the starting gate).
However, a strained vehicle does not always indicate a faulty car axle. This should be seen along with other indications of axle deterioration.
3. Sputtering Sound
The car may struggle to move and produce noises like sputtering, banging, or clunking. This is due to the axle’s inability to transmit power to the wheels adequately.
When the car starts to move and spin the wheels, these awful axle sounds will be audible to anyone around.
4. Wheel Vibrations and Wobbling
Your car may vibrate due to underinflated tires, misaligned wheels, and loose lug nuts. But pay attention to any further indications of axle damage! Once you experience vibrations brought on by a damaged axle or other suspension issues, your car will be hazardous to drive.
5. Misaligned Brake Pads
Once your car axle fails, you will experience some braking problems. As the brake pads start to move and misalign with the wheels and rotors, you may notice that the car skids or slides to a stop. The brakes will finally stop working entirely over time.
An AWD or 4WD vehicle’s driveshaft brake seal may shift and leak a little oil. This will be obvious if you inspect the brake drum.
Grease leaks from axle CV joints are also possible, though less obvious. However, once this happens, the joints will begin to accumulate dirt, dry up, and quickly degenerate over time.
Conclusion – What Is a 2-Axle, 3-Axle, and 4-Axle Vehicle?
Knowing what an axle is and how it works on a vehicle helps. An axle is a central shaft for a rotating wheel or gear, and there are different types of axles: rear axles, front axles, and stub axles.
The number of axles will determine the maximum number of wheels a vehicle can have. A 2-axle car may have three to four wheels. A 3-axle vehicle can have anywhere between six to 10 wheels, while a 4-axle vehicle may have eight to fourteen wheels.
Though most cars and SUVs on the road today have two axles, including motorcycles, generally, there is one axle per pair of wheels, whether a car or a truck.
While axles can support significant weight, they may eventually become weak or damaged over time. Watch out for any potential symptoms, and always do regular checkups to save yourself some potential high repair costs.