A rod knock is is just that, a knocking or a metallic rattling sound. It's often loudest or most noticeable around 30 mph or so. Sometimes you can reduce the sound or even make it go away by disconnecting the spark plug to that cylinder. On older engines with distributors you simply pulled the plug wire to each cylinder until you found the one that reduced the sound. On a modern engine like your Coyote I would simply remove the coil covers if they're still in place and then disconnect the coil pack to the suspect cylinder. Obviously you may have to try more than one cylinder. Don't disconnect more than one at a time. This isn't foolproof, but it can often detect a loose of failed bearing. Again as I suggested earlier a failed or failing bearing will almost always show up in the oil filter media. If you haven't looked here yet, it would pay you to do so.