Dmax LLY 04.5, 10,400 mi.. recently noticed a vibraton at idle, but more disconcerting is at 1500 rpm, ~47mph lightly loaded (small incline) I get a loud buzzing coming from under the truck, so intense that most of the plastic pieces inside the truck start buzzing, like the truck has hit the resonant frquency of every loose piece of material on the beast. Any one else have this happen?


Going to make an appointment to have it checked out..





JJ

I have a mild resonance right at 1500 due to my Magnaflow 4" muffler that's spliced into the OEM 3-1/2" system. I would have them look at exhaust hangers, fittings and heat shields.

My truck is Stock - No mod's yet..





JJ

Yeah, but coincidence of the 1500 rpms made me think that it's an exhaust thing rather than just a muffler thing. The diesel has pretty specific and energetic exhaust wave cycles and the only portion of my exhaust not stock is the replacement muffer.

Think I'll crawl under it tonight and have a look..


JJ

I have a 2004 LLY. 7500mi.


It has a high frequency harmonic. The High Frequency Harmonic translates thru the throttle. Over time it will tend to put your foot to sleep. On occasions I can feel it in the floor board.


I suspect it is comming from the turbo at a particular rpm.


The same issue can be seen in a slight distorting quiver in the outside mirrors at various speeds.


The dealers said Chevy is working on it...


Harold


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