I have the nv5600 in my 2004.5 and I get this noise at low rpms. It sounds kind of what grinding gears would sound like but at a lower frequency. I get it starting off if I ease the clutch out before giving any throttle, but it will make the noise also if I am already in gear and just slow down then give some throttle. If I give a little throttle before letting out clutch (1000ish rpm) no noise. Other than that everything seems to be fine. Is this common? Im new to this so im not sure. If it is what is causing this noise. Thanks in advance.

 

That sounds like mine. Some chattering and growling at low rpm is normal for mine and I know it is in great shape. I check the magnet for wear metal at every change and over fill with 6 qts. Craig

 

The gear rattle is normal at low RPM's. I think it is caused by the engine actually speeding up and slowing down between each power stroke.

I replaced the harmonic balancer with the fluid damper for the 6.7L. Cost of parts was just under $300. It did reduce the rattle but did not eliminate it.

 

if you have a dual mass flywheel, that would be the problem

 

The dual mass was not re-used in our trucks until 2006....worst idea known to man!!!! The 04.5 still had the single mass flywheel.

 

Agreed, the shuddering/vibration is normal when lugging with a NV5600 behind a Cummins.
Wait until you install a HD aftermarket clutch.

Don't lug it. Keep the RPM's above 1800 for the stock clutch. Above 2000RPM with an aftermarket clutch.

You can imagine what the Cummins low RPM lugging vibration does to an auto trans.

 

It's like a 6 cylinder impact wrench!

 

I agree that you must not lug it but I do not agree with the rest of your statement. The max torque is at 1400 RPM on the '03 and early '04's. Max horsepower is at 2900 RPM. These engines are designed to pull at the lower RPM's and the best fuel economy will be obtained if the RPMS are kept at or below 2000 RPM. The auto trans will keep the RPM's in the lower range unless you stick your foot in it. With a manual trans I launch at idle (750 RPM) and slowly increase power after the clutch is fully engaged until I reach 2000 RPM and then shift to the next gear and the RPM will drop to 1500. I never go to full throttle until the engine is at or above 1400 RPM.