Truck Repair: Hammering in Motor

Question
I have a 07 Volvo 780 with a 450 cummins ISX Eng #79015969 dated 07/03 with a 12 speed autoshift this hamering is happing at 1350-1550rpm motor has been rebilt front gears have been replaced new aircompressor and nothing has got rid of the noise the shop that done the work told me they have no idea other places said it's a rod I am at the end of my rope with this

Answer
Was it hammering before the rebuild or just recently? If were talking recently i would pop the top and check make sure there's nothing broke in the valve train. Had alot of issues breaking valve springs, and wiping out cams on that engine. If it's been doing it since you've had work done to it i would be concerned. Those engines do not like dirt at all. They will lock up and throw a rod for anything. Another thing might check into if it's been doing it since your engine work might find out if they lock tighted the cam gears onto the cam if they didn't the gears might have slipped time.