The GMC disc brake calipers on your truck apply the force that will bring you and the load you are carrying to a safe stop. The disc brake calipers are the receiver of the hydraulic pressure being applied to the system. This pressure pushes the piston in the disc brake caliper outward, forcing the brake pads against the disc stopping the vehicle's motion. The seal between the piston and the cylinder walls in the disc brake caliper is the only place hydraulic fluid can leak from this braking component on your GMC truck. Evidence of this seal failing is when brake fluid can be seen on the disc and on the pavement below. This leaking disc brake caliber will cause your braking system to fail leading to clumsy and uneven brake response. If not addressed immediately, total brake failure will be the result. This condition will also be felt in the brake pedal by it becoming soft and could go all the way to the floor when pressure is being applied. The replacing of the GMC disc brake caliper is one of the easiest repairs jobs on the truck. With the front wheel off, the brake hose should be removed. The next step is removing the two bolts holding the disc brake caliper in place over the rotor. Once removed, the new caliper can be put with the brake pads in place on your GMC truck. The only step left is to bleed the hydraulic line by having pressure applied to the system and the nipple on top of the caliper opened permitting the trapped air to escape. With the wheel reattached the GMC truck will be safe to carry a load again.