TAS05CTD610

I was currious as to a noise I heard. I have never heard the truck do it before untill after the box. Right around 1800 to 2200 rpm I hear a ticking (like the injecters are noisier than normal) This is when the quad box is on 60 hp setting. When I turn it off i can hear the injectors but there very very faint. Is the pressure just making them a bit louder?? It's not loud but you can hear it if the radio is off. It only makes the noise in this rpm range, anything lower or higher the motor is smooth and sounds great. I was thinking maybe it was the clearance in the valves but figured it was the injectors. Anybody else hear this?? Just being over protective I guess. Just lost my computer so you know , want to make sure