Look under the truck at the transmission on the drivers side. Find where the shifter arm comes out of the case ... move to the rear of the case about 4 to 5 inches or so and you will see a electrical plug with a wire hooked to up. This controls the passing gear in the Turbo 400. ( see photo
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Follow the wire upward and you should find the switch. GM installed them in different places on different vehicles. Some were under the accelerator pedal, others were under the hood on or around the linkage going to the carburetor or TBI
