The speedometer speed adaptor requires 12v to shift to HI range. Find the HI range wire going from the shifter switch to the electric shift motor on the rear and tap into it to power up the adaptor, that's it...the adaptor case is grounded to the fire wall.
If you follow the wiring from the gear shift lever to the rear you will likely find where the tap was originally done somewhere under the floor. Tap back in with a new wire and route it up to the adaptor.
Mike B
