I am not sure if this is the same as the "shudder". The best I can explain what my truck does it seems to lug. You know like a driving a manual tranny rig up a hill, it starts to lug when you don't downshift. Thats the feeling I get from the f-150. When I either start up a hill or am continunig up one there seems to be a flat spot that I have to anticipate and over accelorate to avoid a bit of shaking. Is this what everyone has been talking about?