Outer Limits 4x4 Board

hey i was just wondering if anyone could help me with a flashing overdrive light in my LN130
its auto of course and the speedo doesnt go and the OD light flashes
is this the speed sensor in the auto and if i order a new one are there different ratio sensors or are they all the same?

Pulled the speedo drive out of the back of the auto today. Wasn't sure what to check for so I checked for voltage and continuity, it didn't have ether so I think it's safe to say it's the drive in the auto that's knackered