Like Sharky said, it's different for everyone. And when it does happen, it'll be gradual. It's not like you're just going to wake up with a deep voice and different-looking face. I'm almost 5 months on T, and my voice started to drop about 1-2 months in, but it's still not low enough that it sounds unambiguously male. And my face looks kind of different than it did 5 months ago, but I'm not sure when that started to happen, because it was so gradual. As far as the T's impact on my ability to pass, I can't really answer that, because I was read as male most of the time for about 2 years before starting T. In all honesty, the biggest change I've noticed being on T these last few months is the amount of hair I've grown, all over my body and the beginnings of some on my face.