I have a 16 SCREW FX4 with the 5.0 that seems to rumble or have a slight vibration when applying brakes lightly and transmission is downshifting into 4th and then 3rd gear while coming to a stop. It almost seems as if the truck is using engine braking. I'm having a hard time deciding if it is a rumble or a vibration. Other than this feeling the truck is very smooth. Does anyone else notice this?