I'm not sure what you've got... the Speedometer Guide.
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There are several adapters that fit into a Type 9 gearbox that gives an electrical output. Do you have something that looks like this? Photos, please.
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That would apply to a set-up where the signal is taken from a wheel or a driveshaft, as documented in the Guide. But not to one where it's taken from the gearbox.
Jonathan