New ISX excessive valvetrain "clatter" - Normal during break in?

We have 3 new T700s in our fleet. Mine is a '12 with 45k, and motor sounds nice and quiet. Was in a different truck last week, still a '12, but with only 3500 miles on it, and the valvetrain is so loud, especially when engine is under light load, such as coming down a hill, etc. Is this normal during break in period? The driver in the 3rd T700 has also about 4,000 miles on it and says the same thing. Will it go away? I got my truck at 33k so I'm not sure if it too did the same thing when it was brand spanking new. BTW they all have the same engine ISX 460. Thanks.

 

I knew it didn't sound right. Nobody else at the shop seemed concerned. Sure enough, it ultimately broke with about 20k on the odometer. The culprit? The wrist pin on the number 5 cylinder was missing it's lock ring from the factory and worked its way loose, scoring the cylinder and causing massive internal damage. Cummins pulled the motor, new cylinder and internals, new turbo, new everything. Two weeks later, she's good as new (hopefully better than new). Someone in engine assembly at Cummins f-ed up during piston assembly!

 

They pulled the motor and completely rebuilt it from bottom to top.