more help needed

[nluvwthtexs]

Everyone on this site has been abe to provide me with so much knoweledge that i didn't have being a first time duramax owner, but i need more. My 05 has developed a knocking, or ticking sound, coming from the front end of the vehicle. It only happens after the truck has warmed up and is moving at low RPM or I'm slowing down. The ticking is in rythem with the RPMs (the higher the RPMs the faster the ticking.) It almost sound like the drive train, but the drive train looks all good. Any ideas on where to start? Thanks

[Nemo]

Mine does this to and has for months, a friend drove it and he said my truck sounds fine(normal)

[usafracer]

Do a search for harmonic resonance and you should find your answer.