The Constant Velocity (CV) joint, also known as the CV axle, plays a crucial role to ensure the smooth running of your vehicle. It transmits power from the transmission to the wheels.
The proper operation of this part is essential for enabling your vehicle to move in both forward and reverse directions. When the CV axle becomes faulty, it may lead to different issues. This article explains the bad CV axle symptoms, causes, and how to prevent them.
What is a CV Axle?
A CV axle or Constant Velocity axle is essentially a shaft that helps transmit power to the wheels even while they are turned without any velocity fluctuations.
Although a CV axle is most commonly used in front-wheel drive vehicles, these types of axles can also be found on all-wheel-drive and some rear-wheel-drive vehicles that use independent suspension.
Early front-wheel-drive configurations like the one seen on the Citroën Traction Avant and the front axles seen on all-wheel-drive vehicles such as Land Rovers used universal joints. These joints are equipped with a cross-shaped metal pivot that sits between two forked carriers.
Even though these joints aren’t of the CV type, they did allow a variation of the angular velocity. While they benefited from being easy to make and strong in construction, they were prone to becoming notchy which would cause difficulties when steering at extreme angles.
Not long after, front-wheel drive configurations were gaining popularity, and cars like the Mini used a compact transverse engine layout.
Universal joints weren’t favorable in such configurations as their limitations were quite evident. To counter this problem, constant velocity joints based on a design by Alfred H. Rzeppa were used. Thanks to Rzeppa’s design, power delivery became smoother, and the axles granted an increased range of angles.
Symptoms of bad CV Axle
The efficient working of the CV axle is very important for the efficient working of the vehicle. As the CV axle goes bad, it produces one of the below-given signs:
- Constant vibration while driving
- Grease oozing out of the inside or the edges of tires
- knocking sound
- Clicking noise on turns
- Bouncy ride
#1. Constant Vibration While Driving.
If you have a worn or damaged CV joint, your vehicle will vibrate even on flat, even surfaces. This is because a bad CV joint will not be able to balance properly during rotation, and as you step on the gas pedal and accelerate, the vibrations will become more severe.
With increased speed, you risk losing control of the vehicle, putting you, your passengers, and other drivers on the road in danger.
You also risk the CV joint disintegrating while driving if it is not repaired or replaced promptly, which is obviously a potentially dangerous situation.
However, identifying this symptom can be difficult because numerous factors can cause vibration while driving.
#2. Grease on the Inside or Edge of the Tires.
The CV axle joint is protected by boots that contain grease while the axle spins, preventing leaks. However, if this grease is thrown into the wheel or tire edges as the axle continues to turn, the resulting lack of lubrication may cause the CV joint to fail prematurely.
When you see grease along the edge of your tire, especially near a tear or tiny crack, it could be a sign of a bad CV joint. You can also turn the wheels at various angles and inspect the outer and inner boots for cracked or split rubber and/or grease.
Remember that replacing a torn boot is less expensive than replacing an axle, so inspect the boot regularly and check the inside edge of the tire for any grease leaks.
#3. Knocking Sound.
When driving, a worn-out CV is known to make a distinct knocking sound. The source of the noise can be found in the inner or outer joints of a front-wheel-drive or rear-wheel drive vehicle, respectively. The sound could also be coming from the differential gears.
Put your vehicle in reverse and drive while rotating from decelerating to accelerating to determine if the knocking sound is caused by a faulty CV joint. If the noises become louder as you drive, it indicates that your CV joint is not functioning properly.
While the knocking noise does not always originate from the CV axle, you must remain vigilant and keep an ear out for it to become rhythmic.
Read More: Reasons Of Engine Knocking
#4. Clicking Noise.
A damaged CV axle frequently makes a loud and distinct clicking sound as you turn the vehicle, and this sound will most likely become louder as you begin to move. The sound may be a loud click at times, or it may feel like a pop, and you will not forget it once you hear it.
To put this to the test, shift into reverse, turn the wheel to one side, and then step on the accelerator. As you move backward in a circle, the pooping or knocking noise will become louder. This is a clear indication that you have a faulty CV joint.
Once you’ve identified the symptom, you should take your vehicle to a service center right away. Depending on the severity of the joint’s condition, you may need to replace the entire shaft assembly in addition to the CV joint.
#5. Bouncy Ride.
If you’re driving down a paved road that’s flat and free of bumps and potholes, any vehicle that’s working normally should be completely stable. However, if your vehicle is bouncing around even on a flat paved road, it could be a sign of a bad CV joint.
As soon as you notice this problem, have a mechanic inspect your suspension components, including your CV joints, to determine the source of the problem. Don’t wait too long, or the situation will worsen, especially if you’re on a bumpy road, putting your safety at risk.
Causes of a Bad CV Axle
Poor lubrication is one of the major causes of a bad CV axle or CV joint. It may also go bad due to many other reasons such as water, contaminants, manufacturing faults, wrong installation, age, or accidents.
Let’s discuss the main causes of a bad CV Axle.
#1. Poor Lubrication.
The proper lubrication of the vehicle’s moving parts is very important to achieve optimum performance. The proper lubrication of the CV axle is crucial to ensure smooth movement and reduce friction.
If there is insufficient lubrication, it may lead to increased friction and accelerated wear of the CV joint and axle components over time.
#2. Manufacturer Faults.
In some cases, production defects, such as the use of low-quality material or poor construction, may be present in a CV axle. These flaws can lead to premature failures of the axle and its components.
#3. Water and Moisture.
If the axle encounters water, moisture may enter the CV joint boot. When the boot is damaged or not correctly closing, moisture can seep in, leading to corrosion and potential damage to the CV axle.
#4. Contaminants.
Your vehicle’s CV axle may come into contact with contaminants (such as gravel, mud, dirt, and debris) while driving. When these contaminants accumulate near the CV joint in large amounts, they can cause surface abrasion, leading to premature wear and tear of the axle.
#5. Poor Installation.
The proper installation of the CV axle is very important for it to work efficiently. The poor or wrong installation of the axle may lead to its premature failure.
#6. Impact or Accidents.
An accident or a significant impact, like encountering a pothole, hitting a curb, or being involved in a collision, may lead to the failure of your car’s CV axle. This force has the potential to cause fractured CV joints, bent shafts, or the loosening of components, all of which can diminish the overall performance of the axle.
#7. Age.
The age of the axle may also cause its failure. As your car ages and accumulates mileage, the CV axle undergoes regular stress. The continuous movement and torque applied over time can lead to wear and tear in the CV axle, ultimately leading to its failure.
How to Prevent a Bad CV Axle
To prevent your CV axle from going bad, you need to follow below-given control measures:
- Proper lubrication of the axle
- Periodically inspection of the CV axle
- Follow the owner’s manual maintenance instructions
- Avoid aggressive driving
- Avoid off-road driving
- Ensure the proper installation of the axle
- Always use good quality axle
- Protect your CV joint boots from water or moisture
Here’s How To Change Your CV Axle
The process below is a general guide on the steps to replace a CV axle. Your vehicle may be slightly or drastically different, depending on the make and model. Refer to your vehicle’s service manual to see the exact steps that you’ll need to follow.
You’ll also notice that we recommend using an impact wrench to remove the axle nut, but note that doing the job by hand is safer when done while the car is on the ground. If you’re following the by-hand route, step five should be performed before jacking up the car.
Let’s do this!
Replacing The CV Axle
- Make sure the vehicle is in Park or that it is in gear with the parking brake set.
- Jack up the car and remove the wheel on the side where you will be working.
- Locate the axle nut. It will be in the direct center of the hub or wheel assembly where you removed the wheel.
- Some vehicles have a cotter pin to secure the axle nut. You’ll need to remove it using pliers to straighten the pin so it can be pulled out. You can spray it with lubricant if it’s rusted or stuck.
- Now it’s time to remove the axle nut. In some cases, this step may require quite a bit of effort. If this is the case, your safety bet is to do this step before jacking the car up. This is where the optional impact wrench will come in handy. The wrench will help you safely remove the axle nut without having to use a pry bar.
- Carefully remove the bolts holding the brake caliper brackets in place and remove the calipers. Instead of dropping the caliper to dangle on the brake line, use a carabiner or other small hook to support the caliper and keep pressure off the brake line.
- Loosed the bolts holding the outer tie rod to the steering knuckle. If there’s another pin here, you’ll again need to use pliers to straighten it out. In some cases, the steering knuckle and tie rod will not want to be separated. This will require a few light taps with a hammer or mallet.
- Remove the bolts holding the hub to the strut tower. You’ll need to keep the nut from turning while unbolting the hub.
- Look further down the axle to see where it meets the transmission. Use your pry bar to pry the axle from the CV joint. You should be able to remove the axle at this point. You might see transmission fluid or have some leak while prying the axle. This is completely fine, but you may want to set up a pan or tray to catch the fluid.
- Insert the new axle into the transmission where the old one was removed. You can use your mallet or a hammer wrapped in a towel to carefully coax the axle into position.
- Attach the new axle to the hub and begin replacing the bolts you removed earlier in the process: Hub/strut tower, Tie Rod/steering knuckle,
- Replace the axle nut. Here, as before, use an impact wrench if you have one to safely tighten the nut. If you don’t have one, get the nut as tight as you can without yanking on it while it’s up on stands.
- Replace the wheel and lower the vehicle. If you need to tighten the axle nut further, it’s best to do it with the vehicle on the ground, so that you can really push on a wrench or bar to tighten without worrying about the vehicle falling.
Replacement Cost of CV Axle
The replacement cost of the CV axle varies according to the area where you live and the type of brand.
Early detection of a damaged CV joint boot can save you a lot of money. If you caught the problem in time, all you may need is a simple boot replacement and repacking of the CV joint with new grease. However, any delays might cost you more as you might have to replace the entire CV joint or drive shaft.
We strongly recommend using genuine CV axle parts provided by a manufacturer because they will be the strongest available, but you can obtain them from other channels at a lower cost.
In a repair shop, the replacement cost of the CV joint boot is between $180 and $350, and a driveshaft replacement can cost between $380 and $800. However, if you perform the service yourself, you can significantly reduce the replacement cost.
FAQs.
What happens if a CV axle is bad?
If the CV Axle begins to fail, one of the vehicle’s wheels will lose power and your car will pull to one side. And if the CV Joint Breaks While Driving, the wheel will no longer turn and the car will not move at all.
How much does it cost to replace a CV axle?
On average, a single axle replacement costs between $300 and $1,500, depending on the type of vehicle and labor hours. The cost of parts ranges between $760 and $1,030, while labor cost is between $170.00 and $180.
What does a CV axle do?
A constant velocity (CV) axle, also known as a half shaft, takes power from the vehicle’s transmission and differential and transfers it to the wheels, allowing the vehicle to drive forward.
How do I know when my CV axle needs replacing?
Drive in a parking lot or open area and make sharp turns at low speeds. If you hear a clicking or popping noise, it’s likely the outer CV joint is worn. While driving at a range of speeds, pay attention to any abnormal vibrations or shaking that may suggest an imbalanced or failing axle.
What happens if a CV axle breaks while driving?
In severe cases, a broken CV joint can lead to a complete loss of control over the vehicle. If the joint breaks while driving at high speeds or while making a sharp turn, it can cause the vehicle to veer uncontrollably or even result in an accident.