I have a 2014 Ram 1500 Express with the 5.7 in it. Every now and then, when first started, it will rap loudly for just a second or two. It seems to happen more often when the outside air temps are hotter, which leads me to believe it's the oil in the hydraulic lifters bleeding back out of them. It doesn't have to sit very long to do it, maybe an hour or so. It does not to it every time though, maybe every 3rd re-start. I have left it overnight at a dealer a couple times to see if it would do it for them and they have evidently not been able to catch it. Just wondering if anyone else has their truck do this, if it's normal it's something I'm fine with. Thanks!