Nice shots. I would have to agree with ShotRaw about the rear end shot (but it seems like you knew that). Not that I am an expert, but from what I have been research for myself, try using a CPL filter to avoid the sun glare on the window or blacken them out in post. Also people have suggested ND filters to help with the overall mood of the scene when shooting cars. I'm still experimenting and learning myself, but your images look good for the equipment used.
Keep on snapping.