Have ya'll heard a bad timing chain in person?
I would not describe it as "diesel", but more of a rythmic "thunk, thunk, thunk,". Now that I have heard one, I would not mistake any other sound for it. My LR tech had me come listen to a RRS that he was about to tear into to replace them. He knew to call me because I had brought up the issue at a previous visit.
I get the "diesel" description. Mine puts out a similar sound, but it is not the chains. Had those done less than 1,000 miles ago. These things are noisy. Among other items, you have injectors, HPFP and fan clutch that can all raise a ruckus.