Ball joints are the spherical bearings which fasten the control arms to the steering knuckles. They consist of a bearing stud and socket enclosed in a casing; all of these parts are made of steel. Almost universally used in the front suspension but can also be found in the rear suspension of a few higher performance autos. Ball joints play a critical role in the safe operation of an automobile's steering and suspension.
Ball Joints Parts for Dodge, Ford, GM Trucks
Sealed ball joints do not require lubrication as they are "lubed for life", but most ball joints have grease fitting and are designed for periodic addition of a lubricant. Standard ball joints will almost always outlive sealed ones because eventually the seal will break, causing the joint to dry out and rust. Adding new lubricant pushes out old and dry lubricant, extending the life of the joint. There is no exact lifespan that can be put on sealed ball joints, but they can fail as early as 80,000 miles. Signs of a failing ball joint start with a clicking, popping or snapping sound when the wheel is turned and eventually turn into a squeaking sound at the end of a stop, when the gas pedal is used and/or also when hitting bumps.
Another symptom could be 'thud' noises coming from front suspension when going over bumps. When your ball joints get dry, you're going to notice a huge increase in the amount of friction. The steering can even stick! If one of these joints fails, the results can be catastrophic. The wheel can become unconstrained, stripping you of control of your vehicle, bringing you to a complete halt.