I've checked out a few threads on here trying to find a similar noise to what I've been dealing with but either haven't dug deep enough, or haven't found one making the right noise. Started about 3 months ago and periodically gets better than worse again, but notice it the most on hot days. Started with only doing this around 50-55 mph but has since progressed to starting right after it shifts through each gear. No codes, no real changes in driving quality (hot days a little sluggish), more so it's just annoying. The groaning seems to be coming from the passenger side somewhere but I haven't been able to pinpoint exactly where. I've had some people throw me ideas such as injectors, torque converter, heat shield vibrations, all sorts of things from all over the truck, so I'm at a loss with even the slightest idea of what it could be. Been running Diesel Kleen through it just about every other fill up and I'd say there is some difference, not enough for me to say it makes it smooth out. Link is a not super great video from a few weeks ago of said sound