2008 GMC Sierra 1500 Pickup Owner's Manual - Page 350

Brake Wear Your vehicle has front disc brakes and could have rear drum brakes or rear disc brakes. Disc brake pads have built-in wear indicators that make a high-pitched warning sound when the brake pads are worn and new pads are needed. The sound can come and go or be heard all the time your vehicle is moving, except when you are pushing on the brake pedal firmly. Some driving conditions or climates can cause a brake squeal when the brakes are first applied or lightly applied. This does not mean something is wrong with the brakes. Properly torqued wheel nuts are necessary to help prevent brake pulsation. When tires are rotated, inspect brake pads for wear and evenly tighten wheel nuts in the proper sequence to torque specifications in Capacities and Specifications on page 5-116. If you have rear drum brakes, they do not have wear indicators, but if you ever hear a rear brake rubbing noise, have the rear brake linings inspected immediately. Rear brake drums should be removed and inspected each time the tires are removed for rotation or changing. Drum brakes have an inspection hole to inspect lining wear during scheduled maintenance. When you have the front brake pads replaced, have the rear brakes inspected, too. Brake linings should always be replaced as complete axle sets. {CAUTION: The brake wear warning sound means that soon the brakes will not work well. That could lead to an accident. When you hear the brake wear warning sound, have your vehicle serviced. Notice: Continuing to drive with worn-out brake pads could result in costly brake repair. 5-38