Walthers O Gauge Oil Pump Gearbox Removal Model #933-2705

[Fish Plate]

I am trying to remove the gearbox on it so I can lubricate the gears. Following the instructions, I unscrewed the motor/gearbox from the bottom of the pump. The next step discusses removing 4 screws and then the cover. There is nothing else mentioned about how to remove the gearbox. The problem I am having, after removing the screw, is removing the gearbox. Something seems to be holding it. The gearbox moves around a bit and the arms on the pump move slightly and the gearbox still won't come out. Would appreciate any replies on how to remove the gearbox. Thanks,