GM has built all cars/trucks with known bad engines. Do a search for silverado rod knock/bearing knock. The problem is two fold. They have crankshaft flex because of an improperly supported crank and the crank is flexing knocking against the bearings. They also have a teflon coated skirtless piston problem where the teflon wears off after the first 1000 miles and leaves the pistons out of tolerance. When you start the engine with either or both problems your will here a rattle/tick/knock. If you look at alldata for TSB's you will find almost every v8 they built since at least 98 shows a tsb for these issues. They also have an engine exchange program for those of us who [non-permissible content removed] loudly enough. They offered me a new engine or a fixed engine and 100k 6yr warranty bumper to bumper. They would not do that unless they had a problem.