The GMC drive and serpentine belt systems use the rotation of the crankshaft to provide the centrifugal power for the many accessories located on the front of your engine. This mechanical power is provided in the most efficient manner possible so the electrical supply of the engine is not overtaxed. The drive and serpentine belt systems are different in their appearance, but not in their function. The drive belt system uses multiple belts to connect one or two components to the crankshaft, but the serpentine belt system is a single-belt system that rotates the pulleys on all components. It is the new style in use today on most GMC vehicles. The GMC drive and serpentine belts have a commonality in that both systems are inspected for the same types of flaws which could cause them to fail. This is evident when chunks are missing or the belt appears scored or frayed. This makes it weaker, which can cause them to fail when supplying power to the components on your GMC truck. The removal of the drive and serpentine belts is different. The tension on your serpentine belt is applied by a tensioner pulley. This is the single point of contact, and when the pressure is released the entire belt can be taken off. The drive belts are taken off by actually loosening the hold down bolts of each accessory like the A/C compressor or power steering pump. Both the drive and serpentine belts have to be in place and functioning for the engine to operate properly. This is why the drive and serpentine belts must be inspected at regular intervals on your GMC truck to ensure they are in proper working order or your truck can or be operated.