Problems with "set smooth"

I have got some issues with my smooth meshes. There are some edges, but i don’t want any. This can be explained best with a picture:

the back looks a bit smaller and is in a darker gray.
But it’s exactly the same material and i’ve modeled it with extrude and moved it on axis, so it should be exactly straight.

what can I do?

Try CTRL-N in edit mode to recalculate the normals outside

it changes a little but doesn’t look better.

You could try selecting the end faces and then press y and click ok to split.

Stick your blend file up so we can have a look

Hazza’s trick worked, it solved the problem. thx @ all


I’ne found that Ctrl N doesn’t always work, but selecting the offending faces and using W>Flip Normals does.