CV joint in a car: what it is responsible for, how it works and how to check for malfunctions

Have you ever heard a strange crunching sound when you turn the steering wheel to a full angle? Or did you feel jerking when accelerating? Most likely to blame CV joint - a part that many drivers only find out about when it breaks. Meanwhile, this is one of the most loaded components in the suspension, without which a modern front-wheel drive (and not only) car simply would not be able to drive normally.

In this article we will figure out what is the CV joint responsible for in a car?, how it works, why it fails and what to do if you suspect a malfunction. You will find out whether it is possible to drive with a faulty CV joint, how much it costs to replace it, and how to distinguish the crunch of a grenade from the knock of a bearing. And also why some CV joints last 200 thousand km, while others break down after 50 thousand.

What is a CV joint and where is it located in a car?

CV joint (constant velocity joint) is a mechanism that transmits torque from the gearbox to the wheels at an angle. Without it, front-wheel drive and all-wheel drive vehicles would not be able to turn their wheels without losing power. People often call this part a “grenade” because of its characteristic shape.

Where to look for CV joints in a car:

• 🔧 External CV joints — located on the wheel side, closer to the hub. They are the easiest to diagnose as they fail more often.
• 🔧 Inner CV joints — are located closer to the gearbox, on the differential side. They break less often, but replacing them is more difficult and expensive.
• 🔧 For all-wheel drive vehicles — CV joints are located on both the front and rear axles (depending on the drive design).

Most modern machines use ball CV joint of the "Rtseppa" type (named after the inventor). It consists of:

• 🔄 Housings with grooves
• 🔄 Inner clip (fist)
• 🔄 Six balls in the separator
• 🔄 Retaining ring and boot

What is the CV joint responsible for in a car: main functions

The main task of the CV joint is transmit torque from the transmission to the wheels without loss, regardless of the steering angle or suspension travel. Without this mechanism:

In addition to transmitting torque, the CV joint performs several other important functions:

• 🔹 Compensates for vibrations — smoothes out impacts from road unevenness, protecting the transmission.
• 🔹 Provides smooth acceleration — without jerking even at the maximum angle of rotation of the wheels.
• 🔹 Reduces load on wheel bearings — distributes force evenly between suspension parts.

It is interesting that on rear-wheel drive cars with a classic layout (front engine, rear drive), CV joints are not used - there the torque is transmitted through the driveshaft. But on machines with independent rear suspension (for example, BMW 5-series or Audi A6) CV joints are also located at the rear.

Signs of a CV joint failure: how to recognize a breakdown

The most obvious symptom of a CV joint problem is crunch when turning. But there are other signs that are worth paying attention to:

Crunching when turning the steering wheel (especially at a full angle) | Jerking when accelerating with the wheels turned out | Vibration on the steering wheel or body at a speed of 20-40 km/h | Extraneous sounds (grinding, knocking) when driving over uneven surfaces | Lubricant leaks on the inside of the wheels (damaged boot) -->

How to distinguish a CV joint crunch from other faults:

• 🔊 CV joint crunches only under load - when turning with acceleration. If the sound occurs when braking or coasting, the problem is most likely in the wheel bearing.
• 🔊 The outer CV joint crunches when turning, internal - when moving in a straight line (for example, when starting off).
• 🔊 The sound gets louder in winter — when cold, the parts shrink and the play becomes more noticeable.

⚠️ Attention! If you heard a CV joint crunch, do not delay diagnosis. A damaged joint can jam the wheel while driving - this will lead to loss of control and an accident. It is especially dangerous to ignore the problem on highways.

To accurately determine which CV joint is crunching, perform a simple test:

1. Turn the steering wheel all the way to the left and drive off - if the crunch is on the right, it’s faulty right outer CV joint.
2. Repeat the same with the steering wheel to the right - a crunch on the left will indicate left outer CV joint.
3. To check the internal CV joints, you need a pit or a lift - with the wheels hanging, check the drive play.

Why do CV joints break: the main causes of breakdowns

Average CV joint resource - 100–150 thousand km, but in practice it can fail after 30 thousand and last 300 thousand km. It all depends on the operating conditions and the quality of the part. Here are the main causes of breakdowns:

The most common cause of failure is boot rupture. When the rubber cracks, sand, water and salt (in winter) get inside the CV joint. This leads to:

• 🔸 Corrosion of balls and grooves
• 🔸 Washing out the lubricant
• 🔸 Accelerated wear of the separator

On some models (for example, Volkswagen Golf or Skoda Octavia) CV joint boots are a weak point from the factory. It is recommended to change them preventively every 50–60 thousand km, even if there is no visible damage.

Is it possible to drive with a faulty CV joint?

Short answer: possible, but highly undesirable. You can’t drive for a long time with a crisp CV joint for three reasons:

⚠️ Attention! If the CV joint is already crunching, this means that the balls and grooves are worn out 30–50%. Further exploitation will lead to:

• 🚗 Wheel jam at speed (especially dangerous on the highway).
• 🚗 Destruction of the drive shaft — replacing it will cost 2–3 times more than a CV joint.
• 🚗 Wheel bearing damage due to beating.

How long can you drive with a crisp CV joint?

• 🔹 External CV joint - from 500 km to 2–3 thousand km (depending on the degree of wear).
• 🔹 Inner CV joint - up to 5–10 thousand km, but the risk of jamming is higher.

If you are forced to drive with a faulty CV joint, take the following precautions:

• 🔸 Avoid sudden acceleration and full steering turns.
• 🔸 Do not load the car (do not tow, do not transport heavy loads).
• 🔸 Check the drive shaft play regularly.

💡

You can drive with a crisp CV joint only to the nearest service station. If the part has already “fallen apart”, the risk of the wheel jamming while driving is ~30% during intensive driving.

How to check the CV joint yourself: step-by-step instructions

Diagnostics of the CV joint can be carried out without a lift, but to accurately check the internal joints you will need a pit or overpass. Here's what to do:

Inspect the boots for cracks and grease leaks | Rock the drive shaft with your hands (play of more than 1-2 mm is a sign of wear) | Drive with the steering wheel turned and listen to the crunch | Check for vibration on the steering wheel during acceleration | Inspect the splines on the shaft (wear or corrosion is a signal for replacement) -->

Checking the outer CV joint:

1. Turn the steering wheel all the way to the left.
2. Drive away and listen - a crunch on the right indicates a malfunction.
3. Repeat the same with the steering wheel to the right.

Checking the inner CV joint:

1. Drive the car onto a pit or lift.
2. Grasp the transmission drive shaft with your hand.
3. Rock the shaft in different planes - play of more than 1-2 mm indicates wear.
4. Inspect the spline joint - if there are signs of corrosion or wear, the CV joint will soon fail.

To visually check the anthers:

• 🔦 Inspect the inside of the wheels - look for traces of grease (it looks like a dark, greasy substance).
• 🔦 Check the integrity of the boot rubber - even small cracks are dangerous.
• 🔦 Pay attention to the clamps - if they are loose, the boot may fly off.

What to do if the boot is torn, but the CV joint is not crunching yet?

If you find damage to the boot, but the CV joint is not yet making any extraneous sounds, proceed as follows:

1. Don't wash your car (especially wheels under pressure) - water will accelerate corrosion.

2. Remove the drive shaft (or contact service) and wash the CV joint with kerosene.

3. Replace the lubricant - use special lithium grease for CV joints (for example, LIQUI MOLY LM47 or Molykote BR2 Plus).

4. Install a new boot - don’t skimp on quality (it’s better to take polyurethane instead of rubber ones).

5. Tighten the clamps - they should fit tightly, without gaps.

If you do this on time, the CV joint will last another 30–50 thousand km without replacement.

Replacing a CV joint: cost, complexity and nuances

The cost of replacing a CV joint depends on the make of the car, the type of joint (external/internal) and the region. On average prices are as follows:

Type of work	Cost (₽)	Opening hours
Replacement of outer CV joint (one)	3 000 – 8 000	1–2 hours
Replacing the inner CV joint (one)	5 000 – 12 000	2–3 hours
Replacing the boot (without removing the CV joint)	1 500 – 3 000	30–60 minutes
Complete replacement of the drive shaft (with CV joints)	8 000 – 20 000	3–5 hours

Is it possible to replace the CV joint yourself? Yes, but it's hard workwhich requires:

• 🔧 Special tools (pullers, torque wrench).
• 🔧 Experience with suspension (you need to properly tighten the hub nut).
• 🔧 Be careful - if you install the CV joint incorrectly, it will quickly fail.

Tips for choosing a new CV joint:

• 🔹 For budget cars (Lada, Renault Logan, Kia Rio) will fit GKN or Metelli.
• 🔹 For premium cars (Audi, BMW, Mercedes) take the original or SKF.
• 🔹 Avoid cheap Chinese analogues - they last 2-3 times less.
• 🔹 Check the package - the box should contain lubricant, dust cover and clamps.

⚠️ Attention! After replacing the CV joint be sure to do a wheel alignment. Even if you haven't touched the tie rods, changing the drive angle can affect handling.

FAQ: Frequently asked questions about CV joints

Is it possible to restore the CV joint or just replace it?

Theoretically, the CV joint can be disassembled, washed and worn parts (balls, separator) replaced. But in practice this is impractical for three reasons:

1. The cost of the repair kit (~2,000 ₽) is comparable to the price of a new CV joint (~3,000–5,000 ₽).
2. The quality of the restored CV joint will be lower - the service life will be reduced by 2-3 times.
3. Not all workshops undertake such repairs due to the complexity and risk of rapid failure.

The exception is rare or very expensive cars, where the original CV joint costs >20,000 rubles.

Which CV joint breaks more often - external or internal?

Repair statistics show that external CV joints fail 3–4 times more often than internal ones. Reasons:

• Larger operating angle (up to 45° versus 20° for the internal one).
• More severe conditions - mud, water, impacts from wheels.
• Smaller size means parts wear out faster.

Inner CV joints usually break due to destruction of the separator (more often on machines with powerful engines, for example, Subaru Impreza or Mitsubishi Lancer Evolution).

How long does a CV joint last after the first signs of failure?

It depends on the degree of wear and operating conditions:

• Light crunch when turning — 5,000–10,000 km.
• Constant crunching noise when accelerating — 1,000–3,000 km.
• Vibration and jerking — 500–1,000 km (risk of jamming is high).

On domestic cars (for example, Lada Vesta or Granta) CV joints “live” longer after the first symptoms than on foreign cars, due to the simpler drive design.

Is it possible to drive without a CV joint boot if it is torn?

Categorically no. Without a boot, the CV joint will last from 500 to 2,000 km (depending on weather and roads). What happens next:

1. In the first 100–200 km, the lubricant will be washed out and accelerated wear will begin.
2. After 500–1,000 km, a crunching sound will appear when turning.
3. After 1,500–2,000 km, the CV joint may jam.

If the boot breaks on the road, temporarily wrap it with electrical tape or a plastic bag with clamps, but don't delay replacement!

What is the difference between CV joints on front-wheel drive and all-wheel drive cars?

Structurally, CV joints on front-wheel drive and all-wheel drive vehicles are similar, but there are key differences:

Characteristics	Front wheel drive	Four-wheel drive
Load	High (engine + transmission weight)	Distributed between axles
Working angle	Up to 45° (outer CV joint)	Up to 30–35° (less due to drive design)
Number of CV joints	2 external + 2 internal	4 external + 4 internal (on some models)
Resource	100–150 thousand km	150–200 thousand km (due to lower loads)

On all-wheel drive vehicles (for example, Toyota RAV4 or Nissan X-Trail) are often used reinforced CV joints with a large number of balls (8 instead of 6) to increase reliability.