<div class="htmlview paragraph"><b>STARTING with the Sturtevant in 1904, transmission developments are reviewed to date. Requirements for successful and satisfactory automatic transmissions are discussed and interpreted in the light of present and future development.</b></div> <div class="htmlview paragraph"><b>Six tables that classify transmissions comprise the nucleus of this part. These tables group the methods of varying the speed; the means of control; the gear engagement or connection; the shifting methods; clutches; and clutch control.</b></div> <div class="htmlview paragraph"><b>THE story of over two million miles of operating experience using the “Mono-Drive” type of automatic transmission on 101 passenger buses in Chicago, is told in the second part of the paper. The mechanical operation of this automatic transmission is explained, and specifications and data are given on the buses in which they are used. A review of the maintenance record of the transmissions concludes the paper.</b></div>