PeterH:
chuff014:
I was going to go a bit simpler and have the arduino keep count from neutral.What will you do if the Arduino triggers a shift and the revs still remain above the threshold? You will design it to avoid the possibility of missed shifts, and test it thoroughly, and it will still find a way to do something you didn't expect. If it's a sequential box it may have a selector barrel which you can get a position sense from.
It only shifts as many gears as it's told to. I'm not sure I follow you.
I can see if there's a barrel.