I pronounce them the same. Like "writer" and "rider", there's no difference for me. As far as I know, it's common in the US to pronounce them the same, but some (or several?) Americans do distinguish one from the other because of a difference in the vowel before T or D. I guess it's called Canadian raising, but I am not completely sure. So, "traitor" and "trader" would be different because the vowels are slightly different.
I am not a native speaker, but I learned to pronounce them the same, so I don't bother.