Simple as that. the authorized ranks have the permissions.user.promote.default node,
but /promote gives a 'you do not have permission' error. I might be missing something but well.

/promote is not a PEX Command.

/pex promote <user> [ladder] and /pex demote <user> [ladder] are. :-)

I figured as much. Yet /promote does use pex. so what permission node would I need to grant? I can not find it anywhere

Which plugin is giving you a /promote command? Their documentation should give you the correct permission nodes. (It may be an "alias" in a plugin.)

Otherwise, you can use PEX Debug Mode to find out if such a permission node exists in any of the plugins you're using. (And if you have any trouble interpreting the Debug Mode output in the console, Pastebin it here and I'll help ya out.)

apparently it's permissions.user.rank.promote. strange. anyways, thanks for the really fast reply!

Ahhh! There ya go— an alias. :-)

For what it's worth, I did an extensive write-up on the /promote command back around Minecraft 1.7.2 in the PEX Wiki— Ranks-(Promotion-and-Demotion) —and somewhere around 1.8 all of that documentation was deleted by one of the original admins/authors/members of the project so I was under the impression it was removed since PEX doesn't print that command in the commands list in-game/in-console anymore.

Thanks for the ticket! I learned something new, more or less. :-)