What does the Universal Joint (U Joint) do?

Universal U joint repair

The universal joint (or U joint) is a component found in rear-wheel drive vehicles. U-joints operate alongside the driveshaft and help the car’s rear wheels to turn. 

Your vehicle will normally have two universal joints connected to one driveshaft. One some larger vehicles there can often be two smaller drive shafts each with two universal joint.  The purpose of the U-joints is to transmit rotating energy on an angle while holding the driveshaft in place, preventing it from creating vibrations from under the vehicle.

Learn more about how the U-joint works >


What are the causes of a failing universal joint?

Worn bearings – The U-joint bearing can wear over time. This is due to the large amount of pressure the component is regularly put under by transmitting all of the engine and gearbox rotating power to the rear wheels.

Lack of lubrication – Lubrication of the universal joint will greatly extend its life. On modern vehicles universal joint bearings are completely sealed, and designed to last the life of the vehicle. If the universal joint bearing seals do get damaged then water and grit will enter the bearing causing bearing damage and rust over time. This can lead to one or more of the universal joint bearings seizing onto the universal joint yoke.

For older cars with grease nipples, we recommend that you ask about getting your vehicle’s universal joints / U-joints greased when you bring your car in for a service. This will allow the part to operate smoothly without wearing.

Height modifications – If modifications have been made to the height of your vehicle, you may find that the universal joints will wear much more quickly as the steeper angle put much more pressure on the universal joint bearings and yoke.

Damaged or bent drive shaft or yoke – if you accidentally belly your vehicle or run over something large it is possible to bend, dent or damage your drive shaft or universal joint yoke. This will put much more strain and pressure onto your universal joints / U joints which means you are likely to have premature universal joint bearing failure.


What are the symptoms of a worn/damaged Universal Joint / U-joint?

Strong vibrations from underneath the vehicle – The driveshaft is carefully balanced so that it works smoothly and doesn’t vibrate. Damage to the universal joint / U-joint can result in the driveshaft becoming unbalanced and vibrating as you drive.

Noises from driveshaft – If you universal joint / U joint bearings are worn out, then as you drive, the driveshaft may produce loud, squeaking noises proportional to your vehicle speed. You may also notice a “clunk” when switching between drive and reverse.

Transmission fluid leaks – By this point, the driveshaft vibrations have damaged the transmission output shaft seal. This usually results in the transmission fluid leaking for the manual / stick shift or automatic transmission rear gear seal where the driveshaft enters the gearbox and pushes onto the output shaft spline. 

Driveshaft failure – Eventually, a broken universal joint / U-joint can cause the driveshaft to become loose from the rest of the vehicle and stop delivering power to the wheels. In this case, your vehicle will likely need a full driveshaft servic. Fixing your universal joint / U-joints early will save you money by preventing further damage to the driveshaft, transmission and under side of your vehicle. 


Universal Joint / U-Joint Ispection & Replacement in Hamilton

Is your vehicle’s universal joints / U-joints in need of replacement? If so, we can help! Grimmer Motors offers reliable, effective replacements for universal joints / U joints, CV joints, and driveshaft components.

Our experienced, qualified and skilled mechanics can give you quality advice on how the problem in your car’s universal joints / U-joints can be fixed. In many cases, it is strongly recommended that you get both universal joints / U-joints replaced at once. This saves additional labour if your other joint breaks.

For universal joints / U-joint replacement in Hamilton, contact Grimmer Motors today!

Please Note – we don’t generally stock or supply just “parts only” for this service. We are a general automotive repair workshop. If you are able to bring your vehicle to us, we can diagnose the problem, find and fit the necessary parts, or organise the appropriate service for you.


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