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How to Tell if You Have a Bad U-Joint

By Alex Palmeri, April 26, 2018

A universal joint, or U-joint, is an integral component used on many rear-wheel, four-wheel and all-wheel-drive vehicles. They are used in pairs and help make up for the difference in height between parts of the drivetrain. For instance, U-joints are commonly used to transmit power from the transmission to the rear differential on bigger vehicles, such as four-wheel drive trucks or SUVs.  

Because they’re constantly moving, they can wear out. If yours is going bad, it’s critical to have a mechanic inspect it right away. A bad U-joint can render the vehicle inoperable and damage other nearby parts. 

Let’s take a look at how a U-joint works. Or, you can skip ahead to see symptoms of a failing one and get repair advice.

How a U-joint works

U-joints are used in pairs at opposite ends of a driveshaft to connect either the transmission to the rear differential or a transfer case to a front differential. They can also be used on an axle to transfer rotational force from a differential to a wheel hub.

Whatever the case, their function is always the same: to allow the up-and-down movement of the driveshaft or axle as the vehicle travels over uneven ground. 

Get it diagnosed by a professional
 

Symptoms of a bad U-joint

Clunking noise when shifting into drive or reverse: By far the most common symptom of a bad U-joint is a loud clunking or banging noise when you put your car into gear. This is due to excessive play in the joint and can also present itself when shifting gears on a manual transmission or upon heavy acceleration and deceleration. 

Vibration while driving: A worn U-joint will cause an axle or driveshaft to lose its balance. As the shaft spins, the vibration created by loose U-joints will be felt inside the vehicle.  

Squeaking noise while driving: If a U-joint loses lubrication, you’ll start to hear a high-pitched squeak while driving. This will sound like squeaking brakes, except the noise will change depending on speed and won’t be tied to using your brakes. You may also hear a chirping noise that can sound like a bad engine belt or pulley but is only heard while moving.

Your car goes into gear, but won’t move: Because the U-joints provide the connection from the transmission or differential to the wheels, a complete failure means your car won’t move. You may also hear a loud banging noise while in gear as the broken piece hits the surrounding area as it rotates. You’ll need to have your car towed to a repair shop. This rarely happens without any of the above warning signs occurring first.

» MORE: Get an estimate for your U-joint repair

U-joint repair advice

U-joints do not have a specific maintenance interval, but most manufacturers do recommend that they be inspected from time to time. Check your owner’s manual for specific mileage and time intervals or have them checked at every oil change. 

Some U-joints can be greased, while others aren’t serviceable. If you have a grease fitting on your U-joint, then you can use an automotive grease gun to lubricate the needles bearings in the cap. Greasing a U-joint can be done at home, but make sure you purchase a good quality, high-temperature grease designed to be used with U-joints. 

If you don’t have this kind of fitting, there’s no service necessary, only inspections as recommended by your owner's manual or outlined above. 

If you begin to experience any of the symptoms listed above, it’s important you call your repair shop immediately. A complete failure of a U-joint can be dangerous and destructive to a vehicle. At the very least, it will leave you stranded and facing a towing bill.

During a U-joint inspection, the technician will inspect the joints for excessive play. If the U-joints are on a driveshaft, they’re typically replaced in pairs, especially on higher-mileage vehicles. After the U-joints are replaced, the driveshaft may need to be rebalanced. 

Considering that U-joints are generally inexpensive and that they’re a very important part of your vehicle, it’s best to use original manufacturer-quality, or OEM, parts. 

The cost to have your U-joints replaced can vary drastically. The major factors here are the cost of parts, labor time and how many joints need to be replaced. When dealing with front axles on four-wheel drive trucks, costs can increase due to the additional labor needed to access the U-joints.

Due to safety concerns, U-joint replacement is best left to the professionals. If you want to save money on replacing your U-joints, and have the appropriate experience and tools, consider removing a driveshaft or axle yourself and bringing it to a shop for them to replace the U-joint and balance the shaft. 

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