On a return recently from Wash. state, on U.S. 101, packing my Lance, chuggin' away up a pretty good grade, it was like someone flipped a switch and.....'PING'! sounded just like the ole gas 'pings' you used to get with too low of octane. After cresting the grade and easin' off, like you flipped the switch again....GONE! Happened a few times on the trip only pullin' grades. I was runnin' Stanadyne every other tank but, like a moron, don't recall if it was happening on tanks with or without! Any ideas???

Thanks ahead, Randy

Sounds like the "burst rattle" that everyone's been talking about. Do a search on this topic. My truck was doing the same thing and so were several others. I have been running power service for the last 3 tankfuls. Double dose on the first and then regular amounts after. I just filled up today and it is totally gone. Not sure why, but I think it may have taken a couple tankfuls to take effect.

Sounds like your pilot injection turning off above 2600 RPM...

Duramax Diesel Pilot to Main Injection Fuel Knock Noise - keywords 6.6 6.6L accelerate engine injector LB7 LLY RPM transition #PIP3422 - (May 10, 2005)
Duramax Diesel Pilot To Main Injection Fuel Knock Noise
2001-2005 Chevrolet Silverado, Kodiak

2001-2005 GMC Sierra, Topkick

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:
The customer concern may be a fuel knock type noise heard at 2500 to 2600 RPM, or when the vehicle is accelerated with a throttle angle above 80%.

Recommendation/Instructions:
The following is an explanation of the fuel knock noise. The Duramax Diesel has what is referred to as pilot fuel injection at lower engine speeds. Pilot fuel injection is defined as a preinjection of a small quantity of fuel, five to twenty crankshaft degrees, before the main fuel injection. This preinjection softens the main injection pressure rise. When the main injection is softened, normal diesel engine combustion noises are less noticeable. At engine speeds above 2600 RPM and a fuel quantity supply greater than 35 cubic millimeters, it is necessary to eliminate pilot injection to meet emission requirements. When driving at or above this engine RPM range, main injection combustion noise may be noticeable. It is normal and not harmful to the engine. When traveling in fifth gear the pilot injection to main injection transition is typically in the 136 kilometers per hour, or 85 miles per hour range. However, it may also be heard under heavy acceleration with throttle angle at or above 80%, when pulling loads up a hill, and during shifts at or above 2600 RPM. Customers that utilize the fifth gear inhibit switch may encounter the pilot injection to main injection transition noise at speeds around 107 kilometers per hour, or 67 miles per hour.

This sound is considered normal and no repairs should be attempted.

T-Wolf, Max,

Thanks for the speedy responses. Sounds like nothing to loose any sleep over.

Pilot injector noise above 2600rpm - that I've notice every morning when the truck is run through the gears. For past 3 months I've added Power Service Diesel Kleen + cetane boost (silver bottle). The rattle noise at high rpm is gone.
It would appear that the basic cause of noise is lack of cetane. This has not been science based study, however it points to a possible fix.

Had the same thing a couple of weeks ago. I think it was a bad tank of fuel. I changed the CAT fuel filter and doubled the fuel treatment and the ping is gone.