I have been told by a couple stealers that the "rapping noise" I hear at the top of torque is normal.


I feel very unsure about it. When shifting from 3-4 and 4-5 it is the noisiest.


Is this normal????


I compare the noise to a lifter rap, or a rod clacking at the top of torque.


There explanation was that it is the "pilot injection" cutting in/out.


Are they putting me on or are they correct, and more importantly do I have a concern???


Thanks

They are right and it is nothing to worry about.



We have 300 hp engines in tractors doing that and they sound like they are fixing to throw a rod, but it is normal.

Yep they're right. The noise you are hearing is just what your Dmax would sound like all the time if it didn't have the pilot injection system.


According to GM's web site, the pilot injection needs to turn off about that 2500 to 2600 RPM range for emission reasons. They don't make clear what the emission problem is above that RPM, but that's the listed reason for turning it off above that RPM range.

Thanks,


Noise doesn't make me feel good, but your explanation parallels the stealers.


The noise also seems to diminish with FTTP additive.


LyleEdited by: kbstinky