Ive got an 05 silverado 1500 with a 6 inch suspension lift and 35 in mud tires. When i put the pedal to the floor you can hear a rattling noise, ive been underneath the truck and pulled on everything and nothing is loose, ive always checked under the hood, checked all the pulleys. Any idea on what it could be? It only makes the rattling noise when you punch it.

 

Could it be pre ignition or pinging? That sounds a lot like rattling.

 

Does the rattle sound like a sheet metal shroud of some kind? Maybe the baffles inside the muffler are rattling. My 04 does that and I'm pretty sure that's where it comes from. Started about 130k miles.

 

Could be the pinging or detonation. Sounds like marbles in a tin can

 

it does sound like marbles in a tin can and rattling of sheet metal. is there a way to see where its coming from, test the muffler to see if its that or anything else?

 

It's sparking before the fuel is burned in the motor. Could be the cause of bad cats. That's why mine was doin it

 

Try putting it on a rack and listen to the muffler with a stethascope

 

One thing you could try is a higher octane gasoline. If you are using 87 octane try a higher one. Run the tank down to under 1/4 and fill it up with the higher octane gas, maybe the 89 octane, and see if that cures it. You will have to put a few miles on it to get the new gas circulating thru the system. If I remember right the lower octane burns faster than the higher octane gas which causes the rattle sound. Does the rattling quit if you let off the pedal a bit? I had a car do that, way back when, and the timing was advanced a couple of degrees too far. Backing that off retarded the spark just enough to make it run quiet. But this was back in the days of carbs, points and condensers. I'm 66 so I go back a ways.