Horrible sounding 7.3

[Fireman40]

This does not happen to my truck but i want to make sure it never does. There are 2 7.3's that run around my neck of the woods that make a horrible srecking kind of metal on metal sound. I think there are 99 or a few years newer. I hear them at the gas station or when there down at the docks. The noise is just horrible and can be heard if its idling or driving down the road. It drowns out the loap sound of a power stroke. I dont know if they have a lot of miles on them or if they never changed the oil. But I want to avoid this noise at all cost. Any ideas of what it is

[Dietoremain]

If they are stock 99's its the infamous torque converter chatter..