Lucky you don't have a 5-speed
You can use all 4 gears in your automatic in 4 hi 4hi locked or 4 low.
in 4 low the auto with shift up rapidly if you don't put the shift lever in 1.
If you have the Adventure model the low range the gear ratio is 4:1!
When in low the engine will be reving up and you will hardly be moving.
The rear axle locker can lonly be activaed when in low range
Low range should be used on steep hills (up or down) and whenever low speed and power is needed.
Have fun and see what it will do.