It is your GMC ball joints that make it possible for the spindle to rotate vertically allowing your truck to maneuver where the driver needs it to go. These are critical steering components that must be routinely filled with grease so their life span can be prolonged for as long as possible. There are two ball joints in each of the front wheel areas on your GMC truck. They come in pairs with an upper and a lower ball joint. These are the components in the A-frame of the vehicle where the spindle is connected. The maintenance of the GMC ball joint should be scheduled during the routine brake jobs that occur approximately every 30,000 miles on your truck. For this maintenance to be performed correctly, the load on the wheels has to be relieved by lifting the truck in the air. This permits the grease to cover the entire ball joint. If there is a load on the wheels, then there will be a load on these joints and the grease will not be able to penetrate and cover its entire surface. Where the grease does not cover, premature wear will begin to occur. The danger of these steering components becoming worn out is that the spindles can become dislodged from the sockets they are resting in which cause the wheel to longer be able to support the weight of the GMC truck. The replacement of the ball joints is not an easy task to complete. Not only does the spring need to be compressed, but the entire pivoting system on the wheel disassembled. This is a time consuming process that most GMC owners wish to avoid. While this task is generally done at a repair shop, it is not required with the correct tools and facility.