CV axle vs. CV joint – How Do They Differ?

Several vehicle components work together to help move your car from point A to point B. Two of such components are the CV axle and CV joints. The CV axle and joints are components of the drivetrain that transmit power from the engine to your wheels. 

While they are components of the drivetrain, they function differently, but unfortunately, people often confuse one for another or even think they are the same components. That’s why a CV axle vs. CV joint side-by-side comparison can make things clearer for an informed decision.

cv axle vs cv joint pros and cons

What is a CV axle?

Constant velocity axle, abbreviated as CV axle, is a type of axle mounted on all front-wheel drive vehicles. It helps transmit power from the engine to the front wheels even when the wheel is turned.

The name “constant velocity” originates from the axle’s design pattern. The speed is constant, so regardless of the direction the outer wheels face, the speed at which power is transferred is the same as the inner section. And because the speed is constant, power transfer will be smooth.

The CV axle houses two CV joints—inner and outer CV joints. While the inner CV joints link the driveshaft to the transmission, the outer CV joints bind the driveshaft to the front wheels. The CV joints help keep the axle in place during different driving conditions while allowing it to rotate to transfer power.

Without the CV joints, the axle will clash or break whenever your vehicle corners or goes through a bump. That is why when the CV joints are faulty, the axle itself will start performing poorly.

It’s also worth noting that while people use CV axle and driveshaft interchangeably, they are not the same. So, CV axle vs. drive shaft, what’s the difference? While both components help convey power from the transmission to the drive wheels, CV axles are only found in FWD vehicles, whereas drive shafts are found in RWD,  4WD, and AWD.

More so, while CV axles use CV joints to connect to other drivetrain components, drive shafts use U joints. So, CV joint vs. U joint, what’s the difference? The CV joints are used in CV axles and turn at a constant speed regardless of the wheel’s direction. In contrast, U joints are used in drive shafts, and their speed is based on how the wheels are turned over the joints.

What is a CV joint?

Constant velocity joint, abbreviated as CV joint, is a coupling tool with bearings and cages that enables the rotation of axles and transmission of power at different intersections. It is a component of the CV axle and is located at the end of the axle.

CV joints house three components— balls, a cage, and an inner raceway, all filled with grease, enclosed in a casing, and covered with a rubber boot. This rubber boot serves as a protective covering for the CV joints. So when it’s damaged, grease will not only leak out, but external bodies like dirt or moisture will enter the joints, causing the joints to fail and, eventually, the axle.

Because CV joint failure often stems from its boot, the best way to prevent CV joints from failing is to replace the CV boots as soon as they wear out. Driving with a torn CV boot affects not only the joints but also the axle.

A bad CV axle will cause a clicking or knocking noise and vibration under your car. If the axle vibrating stems from bad joints, how do you know which joint is bad? Well, here is how to tell which CV joint is bad.

If you hear a clicking or knocking noise when going through a bend or turning the steering angle while accelerating, it’s possibly the outer CV joints. However, if the noise or vibration pops during a straight-line acceleration, the inner CV joint is probably the issue. 

Another bad inner CV joint symptom is vibration under hard acceleration. When the inner joint fails, your car will start vibrating under hard acceleration. As it worsens, the vibration becomes violent, especially under heavy loads.

Another way to spot a bad CV joint is by physically looking out for grease on the CV joint. When its protective boot is bad, the grease in its components will find its way out. If you leave bad CV joints long enough that it totally damages the axle, your car won’t move at all. Remember, the axle transfers power to the wheel to move.

CV axle vs CV joint: Differences

The CV axle and CV joint are linked and work together to deliver engine power to your front wheels. However, both operate at different levels, are built differently, and have different lifespans. Here are the major differences between CV axles and joints.

cv axle vs drive shaft

What do they do?

CV axles house the CV joints and help transfer engine power to your drive wheels. Whereas CV joints help link the axle to both the transmission and drive wheels. Because the Joints are inside the axle, it’s a component of the CV axle.

While the axle houses a rubber boot that protects the CV joints from damage, the CV joints prevent the axle from colliding or breaking when turning or going through a bump.

Materials or composition

CV axles and joints are made of different materials, and that’s because of what is inside them. CV axles are made of SAE grade 41xx seal, also called chrome moly steel or chrome-molybdenum. Some CV axles are also made from SAE grade 10xx steel, commonly called carbon steel.

On the other hand, CV joints are made of rubber and steel. While the components that make up the CV joint—cage, balls, and inner raceway are built with steel, its protective boot is made of rubber.

Replacement cost

Comparing a CV axle vs. CV joint cost is another way to differentiate them. A CV axle replacement costs $300-$1500, depending on the vehicle and labor time. With parts ranging $760-$1100, labor lurks around $170-180

In contrast, a CV joint replacement costs around $900-$1200, with a majority of the cost going for labor fees.

Are CV axles and CV joints the same thing?

CV axle and CV joint are not the same. CV joints are parts of the axle that connect your drive shaft to your transmission and drive wheels. They basically allow the rotation of the axle.

Whereas the axle helps in transmitting engine power to your drive wheels. However, for your wheels to move, both components must work collectively. Without the joints, the axle cannot rotate; if the axle fails to spin, your wheels won’t get any power to move.

That is why when the CV joints are bad, you start seeing the effect on the axle. The noise or other symptoms a bad axle shows are the same as that of a bad joint. So, in comparing a bad CV axle vs. CV joint noise, as well as a bad CV axle vs. CV joint symptoms, they are the same.

Final Words

By now, CV axle vs. CV joint analysis should have made all clear to you where these two differ and how much. While the axle helps deliver engine power from the transmission to the drive wheels, the joints help rotate the axle. They both work together in helping to move your wheels.

To ensure they deliver the correct wheel power, they must be in perfect working condition. In looking out for both components, one thing you must focus on is the rubber boot protecting the joints. If these boots get broken yet still driven, it will not only damage the joints but also the axle, resulting in rough and uncomfortable drives.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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