Whole body moves when clutch depressed?

[dzwestwindsor]

Okay so this seems pretty weird. I've noticed that when I depress the clutch, all the body panels (including the radiator, and the cab it seems) move about a quarter inch backwards relative to the frame! The engine doesn't move anywhere. When I let the clutch out, everything moves back into place.

I don't feel it in the cab- you can only see it from the outside.

Should I be concerned? It's been like this since I got the truck over a year ago, but I'm curious to know why this is happening, or if it's normal.