My Raptor had a similar rattle in the 1200 to 2000 rpm range especially at low speeds either accelerating or decelerating. I fond the issue and secure it and no more rattle.
There are two lines not exactly sure what they are, my instincts tell me they are brake lines. Certainly made of metal. They are routed under the driver side door and held up against the truck frame. They are further protected with a metal coil spring as the two lines jog up and over the frame support. See pic attached. At the right harmonic frequency, somewhere around 1200 to 2000 rpm. They would rattle. I secured them with sound deadening material aluminum/butyl sheets. You do not need to use this, You use just about anything. I used what had. I filled the space between the frame and the coil-snake, see pic with enough material to apply constant pressure against the coil. I did this in a few places as the metal coils are ~10” long.
This completely eliminated the rattle.
There are two lines not exactly sure what they are, my instincts tell me they are brake lines. Certainly made of metal. They are routed under the driver side door and held up against the truck frame. They are further protected with a metal coil spring as the two lines jog up and over the frame support. See pic attached. At the right harmonic frequency, somewhere around 1200 to 2000 rpm. They would rattle. I secured them with sound deadening material aluminum/butyl sheets. You do not need to use this, You use just about anything. I used what had. I filled the space between the frame and the coil-snake, see pic with enough material to apply constant pressure against the coil. I did this in a few places as the metal coils are ~10” long.
This completely eliminated the rattle.