Rattle near feet when accelerating/engine has load

[Jchis372]

I have a 2017 Chevy Silverado 1500 that has a rattle behind the dash near my feet. Ive read all the forums, taken the truck to multiple different mechanics and no one can seem to find a solution. 

 

I keep hearing a “marbles in a pop can” or a “baby rattle” type sound down near my feet/behind the dash whenever I put any type of load/ acceleration on the engine. It seems to be more noticeable when going over 55mph,  especially when towing a boat or enclosed trailer. Although, I did notice that the sound does get quieter when I use a higher octane fuel. 
 

I’ve tried different fuel additives, running only premium fuel, have had the fuel system cleaned by a mechanic and even had the alcohol sensor cleaned. Still, can’t seem to solve my issue.

Has anyone else found a solution to this? Or know what could be wrong?

[CamGTP]

It's spark knock if it goes away with higher octane fuel. I hear it in my truck too when I run 87 octane but basically nothing when I run E85.

 

I can bet if you were watching a live data scan tool that there would be a little spark knock showing and it's usually on the back cylinder that you can start to hear it through the fire wall. I honestly think it's a combo of the loud injectors, spark plug and being able to hear it through the steering shaft boot area of the firewall.

[ftwhite]

Might be exhaust leak. Try soapy water at the manifold and see if you can find bubbles when you blow air up exhaust pipe with shop vac (if yours has air out hook up)