So I have an mx5 nb 6 speed transmission, from what I understand these transmissions are the same internally and differ in bell housing and shifter region. Will the bell housing from rx8 bolt on to the mx5 transmission? Also, I understand that the input shaft is also different. Would the input shaft be able to be swapped with the rx8?

 

Hi,
To your question about using a mx5 transmission with rx8 front bell housing, If going in a rx8 you'll also have to change the rear housing as well from my understanding.
As for swapping the input shaft if the gears are the same size and the input spine is bigger you'll need a bearing to suite it. Is long enough to make it to back of the engine?
then what about sincro's ect.....

So i would say if you want a cheep rx8 gearbox buy a RX8 one to start with. And see if you can find a company to make stronger gears.
If someone else knows better plz explain, or know of a company that already make gears for a rx8.