Yeah, stupid me bought a gearbox from the dutch graigslist and thought it would be fine, well this time i had bad luck. The box wont shift in 5th and 6th gear. Now i wanted to open it up but it wont open more than 5mm, my thought is that some part of the shifting mechanism is broken which prevents it to open it. But maybe i missed something? Does anyone who opened it before have a clue?

btw. its a 716.640 gearbox and i found the exploded views on nemigaparts(its really easy for the people that didnt know it yet)