Honestly I think it's best practice to design a gearbox as if it was made from solid plate, then lighten after the fact. So the outline of the gearbox is defined by the edge of the CIMs, etc - then remove material. Right now it looks like you're making webs and connecting them, and it's a lot easier to mess that up than it is to go the other way. Correct me if I'm wrong though.
For those reading who want to learn, more on pocketing in this great video:
https://www.youtube.com/watch?v=wGmsnD0KQMs