I recently had a problem with the gearshift mounted cable shift switch that is mounted on the frame rail it wouldn't shift for hi and low, it stayed stuck in low, ended up takeing the switch apart and the only problem was is that it was gummy inside, cleaned it and put it back together it worked great, the fitting on the engine side of the switch goes to the hose coming from the engine and the other two are one on top of the other ( I think ) and they go to the vacuum diaphram on the rear end if it is low in the down position your ok if not swap the lines.
