<div class="htmlview paragraph">This paper covers the development and marketing experience, from an engineering point of view, of four-wheel-drive agricultural tractors up to the present time. The information pertains to the Minneapolis-Moline-type of four-wheel-drive and discloses new information on application data. Specific information is given on how to optimize a four-wheel-drive for agricultural applications; design duty cycle and how this duty cycle was confirmed by experimental and field testing. Trends in the use of agricultural tractors as affected by the four-wheel-drive introduction are also given.</div>