Universal joints (also known as U-joints) are a vital connection between your vehicle’s driveshaft and axles. U-joints, allow driveshafts to move up and down along with the suspension while the shaft is moving so you can transmit power. They’re a pivot point that allows two shafts to rotate at the same speed no matter the angle. This flexibility allows the shafts to elongate or shorten to compensate for potholes and speed bumps out on the road. Without the u-joint and the connecting yokes, there would be no way to transmit power from the transmission to the wheels. U-joints are mostly found on rear wheel drive cars, four-wheel drive trucks, and SUVs at both ends of the driveshaft. Front wheel drive vehicles, on the other hand, use CV joints that also compensate for steering.
So, what causes them to squeak? While the bearing components come factory greased, depending on the u-joint there may not be a grease fitting allowing for further lubrication. The bearings of each u-joint twist with each rotation of the driveshaft becoming dry over time. This allows for metal on metal contact which causes a loud squeak as the drive shaft rotates. Other signs indicating u-joint failure include a clunk sound when shifting to drive from reverse, transmission fluid leaking from the rear, and a vibration in your car that strengthens as you pick up speed. Replacing a u-joint is no easy task, so bring your vehicle to an ASE certified mechanic for a replacement today!