Now, I know that this does not pertain exclusively to the 6.4 Powerstroke, but I have to deal with it a lot in my line of work as a Chevrolet technician. Please note the underlined text.


Quoted from General Motors service information:
Some of the above vehicles may exhibit a random ticking noise that is most audible on an engine with a coolant temperature of 70°C (158°F) or higher and from idle to approximately 1500 RPM. The noise usually is most noticeable at the rear of the driver's side front wheel well. Customers may also comment about hearing a tick noise inside the vehicle at idle such as when sitting at a drive through window. All 6600 Duramax™ diesel engines have this condition; however, some are more audible than others. Engine build variation from engine to engine contributes to differences in perceived volume. All Duramax™ engines are manufactured to very close tolerances to meet the durability and reliability standards.

This noise is caused by the relationship of the engine cylinder block, crankshaft journals, bearing inserts and the oil film. This relationship may allow a vibration that resonates through the cylinder block and is heard as a metallic ticking noise. The noise could be described as an irregular ticking or clacking sound, like random typing on a mechanical typewriter.

This condition has been present in diesel engines produced for the last 20 or more years. The overall noise reduction in engines produced today makes this noise seem new when, in fact, it was masked by other noises in the past. Many manufacturers such as Isuzu, Hino, Mitsubishi, and Nissan report a similar condition in their diesel engines. Testing and engine teardowns with this condition reveal no condition that would affect reliability or durability of this engine.

Dealers should not attempt to compare any customer vehicles exhibiting this noise with other similar vehicles as the noise is different from vehicle to vehicle and this may lead to the incorrect conclusion that the vehicle has a condition. This noise is a normal operating characteristic of the engine. This noise has no short or long term effects on the engine. Do not attempt repairs for this noise.


End Quote.

The quietness of the new 6.4 would lend itself to this same characteristic as the International engines are now just as quiet as the Duramaxes have been for a few years now.

Just my $.02