I have 2010 F150 XLT 4x4 with 93,000 miles. The engine / transmission makes a very distinct "rattle"noise, almost a quick grinding noise. The noise only happens when slowing down coming up to a red light/ stop sign. I know for a fact it's not the brakes. When the engine "down shifts" the noise comes from the engine compartment. There is no noise when I accelerate or apply the brake at higher speeds, only

 

Maybe a heat shield has come loose or broken.