Non-Suspension Related Rattle, when truck is ON only..HELP!

[Jason Grzy]

Hi All,

 

I recently went to the dealership with a rattle (2016 denali w/ 47k miles) they told me it was the strut absorbers and whacked me $2,200. On my drive home, Rattle is still there.  My buddy and myself took my truck for a drive to try to figure out where it was coming from and I don't know if this helps anyone identify anything but, we parked the truck and started to bounce it (bounced it standing on the tow hook in front) rattle sounds like its coming from somewhere near the transmission.  What's even more odd, when we shut the truck off to try to hear the rattle better, it stopped even when we tried bouncing harder.  turned the truck on bounced again and rattle is back like the flip of a switch.  Any idea what would change while the truck is not in drive with the engine on vs. off that would cause something to do this? 

Any help is appreciated....this is driving me insane.

[davester]

Exhaust pipe/component?  Transmission mount?

[Jason Grzy]

I don't think so. Like I said, it is only noticeable when you bounce the truck with the engine on.  Once you shut the engine off and bounce the truck the noise is no longer there.  Its like a flip of a switch when the engine is on vs. off.  Truck doesn't have to be moving for this noise to happen.  I cant for the life of me think of what it could be.

[Prong]

Maybe try wiggling the exhaust "flapper" valve near the muffler. Sometimes they like to make noise.