[trularin]

Okay, if you have a electronic Speedo, there may be a angled device connected where the speedo cable would go, That is a transducer. If it has wires instead of a cable that rotates, it is a transducer. It send pulses to the speedo at a rate relative to the rotation of your tail shaft.

Kirkham is right about the gears, which beggs a question: Has this ever worked before?

Are you trying to connect a speedo that is electronic or mechanical ( cable driven )?