Elephant sound when hard accelerating

[Josh77]

Hello Everyone. My 2021 Express 3500 has developed an elephant-type noise when hard accelerating. It seems to happen whenever going from steadily giving it gas to a hard acceleration. The noise seems to be happening more frequently. From what I can tell, the noise is originating from the engine, but the transmission is also a possibility.

A recording of the noise is below:


Any help is greatly appreciated.

[MountainManJoe]

Welcome to the forum.

I have never heard a sound like that.

Check for:
loose intake pieces or missing resonator
loose exhaust heat shields or other things touching the exhaust
exhaust leaks
things touching the serpentine belt.
Things touching the driveshaft
etc...

[copper128]

That sounds like a heat shield rattle to me.