There are numerous 4wd systems; many are sophisticated and automatically controlled but basic rules apply to all. Not just plow and work truck's, but SUV's also need to pay attention to tire size. All the tire's must be the same diameter, notice we did not say the same size! Measuring tire size can be tricky. We use a "stagger gauge", like they use on race cars, but you can use a level to find the top of the tire relative to the ground. With the vehicle on flat ground, measure from the ground to the level. The tire's should be within a 1/4 inch (not very much) of each other.
 

Also remember to disengage 4wd, in applicable systems, when leaving slippery surfaces! 4wd is not intended for use on dry pavement. Following these simple guidelines can save you lot's of money in the future, on the costly repair's that possibly could have been avoided!