Universal joints are used on rear wheel drive vehicles. They allow the driveshaft to transfer torque at different angles as the vehicle travels over bumps in the road. If worn, universal joints will cause a clunk when the transmission is place into gear. They also cause driveline vibrations that increase with vehicle speed. A U-joint consists of the spider joint, four caps and their retaining clips. Each cap contains needle bearings held on place with thick grease. These bearings allow for high speed operation. As the joint wears, it can become loose and lose vital lubrication.