A pair of aftermarket shift levers on a 4 wheel drive vehicle (not all wheel drive) that attaches to the transfer case allowing the driver to direct power from the engine to the front, rear, or both drive axles.
Two gear shift used for classic semi trucks used to expand the gear ratio for more power most combinations are 5x4, 4x4, 5x3. Shifted useing 5x4 combination main box in 1st the second box shift 1-4 the main box to 2nd then second box 1-4 etc.....
