Sorry for putting it in the wrong section of the forums (the first one was in discussions) I have been trying a whole day to find it, I know its somewhere in audio.rar but its password protected. So I cant listen to which one it is. I really wanna replace it, to add a better sound.
You can't replace the default ingame sounds as they're encrypted due to copyright. The only thing you can do, is to put them on other vehicles or make a mod yourself with custom sounds.