Rumors say that it happens after the owners replace the plugs. Remember these trucks have 100,000 mile plugs in them. When the plugs are replaced the person over tightens them and with an aluminum block it just weakens the threads. Plus most of us go with a different brand of spark plug and the thread lengths are different and all this combined spells problems around 115,000 to 130,000 miles! Weakened threads and not enough threads just blow out!
