[KGBnut]

I've had some very surprising rattles through the years. The trickiest one was only at certain RPMs and sounded like it was under the car, or on the firewall.

I spent a lot of time walking around the car and banging on every panel I could think of trying to force it to rattle. It turned out that one of the wings on the top of the radiator, the ones that the hood rods bolt to, had broken off of the radiator. The rod would vibrate and transfer the sound to the firewall.

Keep banging on panels, brake rods, running boards, etc. trying to force it to rattle. You will find it.

Ken