5 Symptoms To Look Out For A Bad U-joint

You have used a car, truck or at least buses for transportation, right? Perhaps you have even experienced vehicle breakdown and failure due to faulty operations. 


Most breakdowns usually happen due to loss of power or the inability to transfer power from the engine to the wheels. The part of the vehicle which transmits power to the wheels is the transmission system which plays an integral role in the vehicle’s operation. If your transmission system fails or is faulty, your vehicle cannot move.


U-Joints are one of the main components of the transmission system. They are used to transfer power to the wheels of your vehicle and also to provide height misalignment during bumps and pits. 

A U-joint failure might lead to complete breakdown of the car. If a U-joint fails while the vehicle is running, it might cause fatal accidents. 

This article explains the basic operation of the U-joint, its importance in the transmission system, bad U-joint symptoms to look out for, as well as best practices to identify and repair a faulty U-joint.

For more in-depth information on U-joints, their classification and the theories and principles behind their operation, you can look at this article

How to fit and operate a U-joint


The Universal joint, a.k.a. the U-joint is a rigid joint or coupling whose axis or rods are inclined toward each other at a 90-degree angle.

The job of the U-joint is to transfer rotational power from the engine onto the wheels of the vehicle. One end of the U-joint is connected to the engine’s output shaft, and the other end is connected to the axle of the wheels.

U-joints are also used to adjust the height misalignment between the power transmission and the rear axle. They change the direction of rotational power and then transmit it to the wheels.

U-joints are not a common, velocity-type joint. They are designed to provide torque and avoid speed fluctuations. One of their great features is that they are noise-free and reliable in operation. Here is a video that may help you to better understand the mechanism of operation of a U-joint.

A Simple U-joint assembly

A Simple U-joint assembly

How to Identify a Bad U-joint

U-joints are an integral part of the drive shaft power transmission system. They transfer power from the engine to the wheels and also move the drive shaft up and down in the case of bumps and pits.

A bad U-joint may not be able to transfer power from the engine to the rear wheels, thus breaking the link between them. It may also lead to the breakdown of the vehicle while driving.

If a U-joint failure occurs, it may lead to the detachment of the joint or hinge from the drive system. If the U-joint fails while driving, you will lose control over your vehicle and it may tip over, leading to fatal accidents and irreversible damage.

A broken U-joint may impair the brake line, the power transmission and other parts of the vehicle and can cause damage to the vehicle or the driver.

So, it is of vital importance to check your U-joints periodically and replace them if necessary. Now let us look at the various symptoms of a bad U-joint so that you can avoid a vehicle breakdown due to U-joint failure while driving.

identify a bad U-joint

#1. Loss of lubrication

The bearing portion of the Universal joint twists and turns with each joint rotation. The bearing parts are always supplied with the required amount of grease or oil lubrication in the factory.

Lubricants are used to avoid the metal-to-metal contact in the bearings as well as to prevent overheating. After a continuous operation, the grease lubricant inside the bearing may evaporate or be pushed out, thus leaving the U-joint without lubrication. 

If the bearing is lubricant-free, you might hear a small squeaky sound while driving your car, although it may not be audible at speeds over 10-15 mph. 

The squeaky sound is a warning signal about the bad condition of the U-joint. The U-joint must be serviced by a mechanic, and lubricants must be added to increase its lifespan.

#2. Clunking Noise

Another sound that should spike your awareness is a small “clunk,” like the sound you hear when you switch your vehicle from normal drive to reverse. This “clunk” indicates the excess clearance in the U-joint bearing during the forward drive and its hard stop during the reverse drive. 

This is what you hear in the next stage of lubrication loss. It happens when the U-joint is in use with insufficient grease or lubricant. 

Servicing or greasing the U-joint may prevent this problem by extending the lifespan of the bearing. However, the damage to the bearing cannot be reversed, and a new U-joint must be replaced soon.

#3. Vibration in Vehicles

Your vehicle may experience vibration and imbalance when your U-joint is in a bad state or is broken. In the case of vibration, the U-joint bearing is worn enough to allow the rotation of the drive shaft outside its normal path. 

And since the drive shaft rotates at higher speeds, the vibrations are of high frequency. Thus, the worn U-joint may damage other parts of the vehicle as well, including the transmission system. 

It’s important to point out that these vibrations are caused by a fully worn-out U-joint bearing. You must get the the worn U-joint bearing replaced with a new one by a professional mechanic or service person. The new U-joint must operate with minimum maintenance and have longer life span.

#4. Transmission Fluid Leak

A badly worn U-joint causes vibration in the tail shaft bushing and damages the output shaft seal. When damaged, the output shaft seal causes leakage of transmission fluid from the rear end of the vehicle. You must check the rear of the vehicle for transmission leaks. 

The source of leakage must be detected and a suitable solution must be executed. The U-joint must be replaced if the diagnosis shows that it has caused the leakage of transmission fluid.

#5. Drive Shaft Breakdown

In the case of U-joint failure, the entire drive shaft assembly might break down or fall off your vehicle. You might have even seen some vehicles at the roadside with the drive shaft on the ground.

Drive shaft breakdown usually occurs due to the ultimate failure of U-joints. In that scenario, the drive shaft is literally broken and lies on the road. At this point, the bad U-joint is beyond repair, and the entire drive shaft should be replaced. 

Unfortunately, drive shaft breakage also leads to damage in other vehicle components. This may turn fatal if the drive shaft breaks while driving at a high speed.

Drive shaft breakdown might leave you helpless in the middle of the road. That’s why it is a good practice to periodically check and maintain the U-joints of your vehicle. If you fail to do that, your bad U-joints may cause damage to other vehicle parts, or even lead to a fatal accident for you and others driving nearby.

car under the sun

How Long Can You Drive With a Bad U-Joint

You must be able to identify the state of a bad U-joint so that you can estimate how much further your vehicle can travel. A vehicle with a bad U-joint breaks down in few hundred miles at the maximum. If above symptom are heavy such as transmission fluid leakage, it is recommended that you do not drive your vehicle as the U-joint may break down anytime which will cause damage to the brake line, transmission line, drive shaft, etc.

See more: 5 Leaky Intake Manifold Gasket Symptoms You Need To Know!

How to Repair a Bad U-joint

There are several ways to identify a faulty U-joint. Firstly, it causes vibration during acceleration and deceleration of the vehicle, and it also makes the drive shaft vibrate. 

Secondly, there is a clunking sound that occurs when you shift from forward drive to reverse. 

car repair

You should check for lubricant or transmission fluid leakage caused by the U-joint failure. It is possible to stop a small lubricant leakage and drive your vehicle to the nearest mechanic shop. For that purpose, there are ready made seals that can be used to stop the leakage temporarily. 

Transmission fluid or lubricants can be added to extend the lifespan of a U-joint. In the case of transmission fluid leakage, you are advised to contact your nearby service person for replacing your U-joint. 

An ATP seal can be pumped inside the U-joint to stop the leakage of lubricants from the U-joints. Here you will find the ATP seal product.

The girl is opening the lid of the car

Manual transmission fluid can be used as refill agent to make up for lost fluid, but that’s as far as road repairs go. . The next step is to move our vehicle to the nearest service center for U-joint replacement. Click here to access the manual transmission fluid link suitable for U-joints.

In the case of a complete breakdown of the drive shaft, your best option is to contact a mechanic or service person then tow your car to their service station. The complete drive shaft assembly must be replaced as it cannot be repaired. 

It is not advisable to disassemble or work on the U-joints without proper knowledge and experience. If you are confident enough to operate on your own, you can follow this step by step guide to repair your U-joints. Please watch this video for guidelines that might help you check, dismantle and repair a U-joint.

See more: How To Know If There Is Water In The Gas Tank?


Symptom #5 might leave you helpless and distressed on the highway or road. Some weird accidents while driving may even turn fatal to you and the people nearby.

U-joints are an integral part of the transmission system. Without them power from engine will never reach the wheels. A bad U-joint must be replaced at the earlier stages of failure or it may damage important vehicle components such as the braking line, transmission system, drive shaft assembly, etc. 

It is highly advisable to periodically check and maintain the U-joint as failure to do so almost always leads to fatal accidents while driving. It causes you to lose control over the vehicle which might then tip over. You may also cause damage to the vehicles and people in your vicinity because a U-joint may literally break away from your vehicle and hurt others.

Hand of auto mechanic with a wrench. Car repair

Hopefully, this article helped you to better understand the role of U-joints in the transmission system, the symptoms of a bad U-joint, and the importance of proper U-joint maintenance. You have now gained knowledge about the consequences and possible damage caused due to poor maintenance, so you know to periodically and carefully check your vehicle.

If you liked this article, please share it with your friends and family so it might be helpful to them as well. If you have any suggestions and useful tips about bad U-joint failures you have experienced, please share them in the comments below.


Hi there! I’m Jordan, chief editor of Crush the Road and I’m a self-confessed automative fanatic. Cars or vehicles has always been a passion of mine and will always be my favorite pastime. Now that I am married and has one adorable son, I have the time to write and share my personal experiences with other automative enthusiasts like me. Welcome to my fantastic blog!

Click Here to Leave a Comment Below 1 comments
Avatar for Sue
Sue - December 19, 2021

Hey Jordan, I have a question. My son drives a Ford Explorer that is shaking as he excellerates and he was told it is a spark plug missing or something like that and I’m wondering if it could be a ujoint because the whole vehicle shakes so badly. Would a miss in the engine cause the whole vehicle to shake? Your article on ujoints is very helpful to me because my van needs ujoint repair and the way you describe the shaking matches what his explorer is doing.
Thanks for the article and information!


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