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We have a 2016 Yukon 6.2L which developed a rattle at approximately 60k miles. Initially I believed the source of the rattle was a heat shield, but everything seems to be tight. It has been to the dealer twice and no progress has been made to resolve the issue. The first time they dismissed the problem and called it "normal" and the second time they believe it's a broken baffle weld in the muffler. What do you think? Thanks in advance

 

Video with several angles from under the vehicle demonstrating the issue. The problem only surfaces when the vehicle inters v4 mode. Also, the rattle is so loud it is picked up by the Knock Sensors and it pulling timing. Scan performed with HP Tuners VCM Scanner.

 

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Have you tried some wire or zip ties to hold the exhaust flapper open to see if the sound changes??

 

As for the knock, I always see knock on these trucks even without a rattle. It's worse if someone doesn't run 91+ octane like they are suppose to in a 6.2. Even the 5.3's on 87 octane knock worse than when on 89+.

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Thanks for the response.

 

Have I tested the flapper, yes. I used a piece of wire and tested both open and closed. Same results.

 

The knock is only recorded when in 4v mode. I am monitoring PID - Displacement on Demand Request and as soon as it flips to YES, the knocking starts. It's pulling about 4 degrees. While running in v8 mode there is no knock.

 

image.thumb.png.9f9729f462c1caaf3bc913c86ba5f481.png

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Beats me. Anyway I look at it tells me that the engine needs to be opened up and that's expensive.

 

Turning off the DoD is cheap and would stop all these problems.

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From the first two viewing angles it almost sounds like your driveshaft was installed upside down. Common mistake, but you may have already checked that out. 
The last viewpoint makes me wonder if you have something going on in, above, around the frame area near the body. Are you running with a spare tire hanging in the rear? Have you checked up in that area to see if you can hear anything. Tried using a compressor with an air wand to see if you can duplicate the sound while parked. Could you have part of your “honeycomb” rattling around inside the exhaust (a piece broken off from inside the cat)? I’m just pulling at straws here to throw ideas out there of similar things I’ve found. 
Originally I would have thought the same thing you did...a loose heat shield. Let us know if you ever found the problem. 

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