Update : after finding a video on Youtube where someone had the same sound as my Ram I've fixed the issue - it was loose bolts on the flange to exhaust manifold drivers side. Someone had already put a split flange on it and the passenger side so its likely had the same issue previously where the flange rusts or breaks and is loose. After tightening the loose bolts my 4.7l exhaust is back to normal noisewise.

Question for anyone that knows - The bolts don't have lock washers on them and this likely is the reason they loosened over time - Should I install lock washers and/or blue threadlocker?

 

First, I'm going to thank you for improving our forum by posting the FIX ! Way too many people post a problem then never report back.

What ever you use to ensure that it doesn't back out, make sure its up for the temperature at that area. You could try some variation of header fastener locks instead, they are mechanical and don't rely on spring tension. Is it just a through bolt with a nut on the other side? If so you might want to go with a distressed thread type nut - those tend to not change much with temperature.... or a double nut and jam them together.