Cracked flexplate - a welcome sight over the engine, but still a PITA! An interesting noise developed in the oil pan this morning and I'm a bit at a loss as to what it is. Haven't dropped the pan and probably wont have the time to do so for a bit. I've heard just about every kind of noise from a small block but this one is different. It sounds like something rattling around near the crank main and towards the rear of the engine (stethoscope tracked it down). It sounds similar to a dust shield rattle and is definitely not a knock like rod bearings produce. It only makes the rattling noise when at 650rpm but immediately vanishes at anything above that, whether under load or not. The truck runs just fine, not stumbling , no hesitation and rev'd up to 2000rpm sounds great, as if nothing is wrong. Oil pressure is as it has always been but the noise sounds like its coming from that general location. There are a few things which I have not experienced before and I'm wondering if it could be one of these; oil pump on the way out or pickup worked loose, cracked flex plate or sloppy wristpin on the 7 or 8 cylinder. If I had to guess what the noise was I'd be leaning toward the oil pump pickup just barely making contact with the crank because of the hollow type sound. Any thoughts?