Pickleforks work fine for many of these things. Obviously they require a hammer, which you stated you didn't want to use on your gearbox, which is probably smart...so a jaw puller was initially suggested.

Did you still have a question? I'm a little confused by this sequence of comments so-far as they seem to be going in a circle...and it seems the first response accurately answered your first question...plus you now have a hammer & pickle fork alternative suggestion.