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Universal joints are commonly found on the driveshaft of rear-wheel drive cars and trucks. As they wear out, excess vibration or clunking noises may become noticeable.



What is a Universal Joint?

Universal joints allow the transfer of rotational energy without needing a “straight shot” to the fastener or rotating part. Universal joints are an important part of all rear-wheel and four-wheel drive drivetrains.

How do Universal Joints Work?

A vehicle’s engine and transmission are bolted directly to the frame or body, but the rear axle must swing up and down as you drive over bumps in the road. Universal joints allow the rotational energy of the engine to be transmitted to the rear axle of the vehicle.

Because the angle between the transmission and rear axle changes constantly as you drive, universal joints are required to keep them attached to one another. U-joints are a regular maintenance item on many rear-wheel and four-wheel drive vehicles.

How are Universal Joints Made?

Universal joints need to be strong and sturdy. They are constructed of forged and machined steel, using heavy factory machinery in a mass-production environment. Custom universal joint components can be manufactured by local prototype shops.

For the vast majority of vehicle applications, all that’s needed is a factory replacement or aftermarket universal joint. Universal joints come in a variety of sizes to fit most applications.

Why do Universal Joints Fail?

  • Under normal driving conditions, universal joints fail due to vibration and heat.
  • An unbalanced driveshaft may cause premature universal joint failure.
  • Failure to grease the universal joints during routine maintenance may cause premature failure.

Common Symptoms of Universal Joint Failure?

  • A loud clunking noise may be heard when starting from a stop.
  • Vibration that gets worse as engine RPMs increase may indicate a worn universal joint.
  • A slight lag may be present when starting from a stop, indicating a worn universal joint that needs to be replaced.

What are the Implications of Universal Joint Failure?

  • If the universal joint fails completely, the driveshaft may fall onto the road surface while driving.
  • Driveshaft vibration puts additional stress on the transmission’s output shaft or coupling and seal, which may result in damage to the vehicle’s transmission or other drivetrain parts.

Universal joints are an important part of your vehicle’s drivetrain. If you notice excessive vibration or noise when starting off or accelerating, start the repair process by diagnosing the issue.

If you have questions or concerns about universal joints or any of your vehicle’s components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.