The only solution is to not look back. It is quite irritating, especially at twilight or nighttime. There's just something wrong with the lighting system in gt5. It seems to reset to a base level every time you look around and then gradually adjust to where it wants to be, which is often not where it was before you looked. The Spirit R seems to make it worse as I think it has a tinted rear window which makes rear-view itself quite dark, but it happens in basically every premium I've driven.
In some cars with tinted stripes across the front, you can see cloud detail that is invisible through the rest of the windscreen, and would make the sky look much nicer if you could see it.
I've also noticed that looking in different directions resets some/all of the sound samples, like engines, horns, and(very funny at rally race starts) crowd noise. This happens in exterior views as well.
Don't know what might be wrong with your gears, sorry.
