Low range would be used in situations such as pulling a heavy load (like pulling someone out of a ditch) or possibly if you had to climb a steep grade that required the use of 4wd. Cotrary to what some might tell you, do not use low without locking the hubs. Some will tell you that you can use low range in 2wd mode, but that can lead to axle/driveshaft failure. This is because the low range multiplies the torque, usually 2X what is going in. This can exeed the rating of the axles/U joints if the front isn't locked in to allow the torque to be evenly spread to all 4 wheels.

Bill Burmeister