problem in 3D mesh gambit

yann

hi

i am trying to study a flow over a truck, and especially the end part of the truck and how reduce the drag. i am starting with a simple model: cube, then i try to add some kind of vanes system. then i crated a brick around the previous volume. then i substract the brick with the truck and try to mesh the volume, but there is an error during the meshing.

can someone tell me if i am doing it correctly, and how can i mesh.

thank you yann