That's also what I've been wondering too. I've been taking classical singing classes for 2 years and a half and I wanna develop a career in this direction. The thing is, trying to get some grunting going is just so tempting. Just for fun, that is. I've been thinking to try this style as well, just for experimenting, but I'm fucking scared of what might happen to my singing voice if I try that and something bad happens.
Anyhow, I heard about this guy who is in a local black metal band, so he does lots of 'shrieking' stuff, that he has used his voice so much in this direction, that he actually developed some kind of an inner bulge that somehow stops him from doing clean vocals, but it also eases his way to grunting. I also thought it might be a nodule, but apparently it's not in the chords' area.
Anyhow, another friend of mine, who sings classically, has forced her voice a lot, she didn't use her diaphragm at all, so she just kept on forcing her chords' in order to obtain the proper volume and consistence, also damaging the correct position of the palate to achieve that.
Now, I'm definitely not sure about that, it might just be some silly method of explanation, but I think this is also the effect grunting has on your voice. It does require a lot of diaphragm support as well, but practically, the whole area around the chords, the larynx and all gets swollen as hell, because of the irritation this kind of efforts provoke.
I think. So, if someone really knows this phenomenon and how to explain it better, I'm really eager to find out as well.
/edit: Hah, I forgot about the most important part, the conclusion, that is.
I suppose it does not affect your range. It normally shouldn't, as long as you continue using your clean voice as well. I mean, your range might go down a bit even if you spend, let's say, one month without singing at full potential, even if you don't do any kind of grunting at all. By simply not using it. I also think it doesn't affect your speaking voice too much either, we have so many metal singers as proof. I only think that, after having achieved a proper, healthy, constructive and non-fatiguing technique of clear singing, grunting might damage the quality of your voice. Not the tone, not the depth, just the quality. I've noticed that people who do grunting have some kind of an emptiness of their voice, a bit airy and not so 'present'. I really hope you can understand me, 'cause honestly, now that I'm reading my post again, I can't.
