4 wheel to 2 wheel drive question

I have a Rancher 350FE. It has a button on the front right to switch from 2 wheel to 4 wheel drive. I have had it for 2 years and it has never worked. I just keep it in 4 wheel drive. What is that switch called? Can it be replaced? Is it needed? I have been told it is better on the roads to use 2 wd instead of 4wd.

4 wheel to 2 wheel drive question

I have a Rancher 350FE. It has a button on the front right to switch from 2 wheel to 4 wheel drive. I have had it for 2 years and it has never worked. I just keep it in 4 wheel drive. What is that switch called? Can it be replaced? Is it needed? I have been told it is better on the roads to use 2 wd instead of 4wd.