Full load gov'd speed is 3,100 no load gov'd speed is 3,600 but can spike to 3,700. I have seen a tad higher when a flexplate let go.

Normally you should be able to rev it to 3,600 in neutral. Nothing wrong with that. The cam will let go at 4,100rpm. If you stay at 3,600rpm for more than a few minutes the water temp will climb pretty good.

If it revs up to 3,100rpm and goes, bahp bahp bahp, you are running out of fuel pressure, either in the low pressure side between the lift pump, or in the common rail with the high pressure pump not being able to keep up.

If your truck only runs up to 3,100 in neutral with your foot no the floor, you have a minor problem, either with full, or air delivery.

It should not run over 3,200rpm with any significant load. Traveling in gear is more than enough load to pull the motor down to 3,200.


Merrick