2001 GMC C1500 Timing Belt or Chain

HI there, This is a chain drive engine, as with belts there is no set interval for replacement, often they can last the life of the engine, but tell tail sighs can show up such as rattle in the front of the motor, as you will see in the pic, there is no chain tensioner and you can pick up chain slop by feeling this slack take up when you rotate the engine by hand, a trained mechanic will be able to detect chain stretch this way. mark (mhpautos)