Without the GMC power steering pump on your vehicle working properly, maneuvering of it will be difficult, if not impossible, for the driver to accomplish. Symptoms of this failure can be felt in the steering wheel when it is sluggish and jerky feeling in the turning process. The power steering pump itself usually will not fail by simply losing its ability to produce a pressurized fluid. The failure occurs when the seal on the pulley shaft will no longer be able to contain the hydraulic fluid in the pump. This condition can be observed with the presence of hydraulic fluid on the inside portion of the pulley and in extreme cases the formation of a puddle below the power steering pump on the pavement under your GMC truck. The seal on the shaft of the GMC power steering pump is made of a polymer which in time will wear out. Replacement of the entire unit is then necessary since the rebuilding of this pump manually is very time consuming and requires special tools. If you notice your power steering pump has a leak, the very first thing to do is to fill the reservoir up to the maximum level before driving it again. This will make it possible for you to go to the repair shop so the power steering pump can be replaced. If you continue to drive your GMC truck in this condition, the leak will do nothing but increase. Each time the fluid level drops below the minimum level, air will be introduced into the system causes the steering to increase in its difficulty of controlling the direction of the GMC truck. This loss of control over the steering of the vehicle is not desired or safe for not only the driver but others on the road new this vehicle.