We got a 18" Magnaflow muffler installed about a month or two ago and since day one there has been annoying vibration sound at low RPM and speed. Took it back to the mechanic and he couldn't tell where it was coming from. It's definitely coming from the middle of the truck somewhere.
We cannot reproduce the sound in neutral.
Everything seems tight underneath, so I'm not sure whats going on. The mechanic states it could just be resonance, but I'm not buying it.
It sounds like a heatshield vibration, but he said they are fine.
