Sigh. For those that missed it last time...
http://www.subsim.com/radioroom/show...ight=promotion specifically
http://www.subsim.com/radioroom/show...14&postcount=8
And to reiterate my last line again, it can be done in SH3 AND GWX, exactly as Rhodes stated. Likewise you can promote a sailor to a Petty Officer in the same fashion.