The object of this paper is to re-assess the existing principles used in the design of synchronized mechanical transmissions from the point of view of synchronizer duty. By a logical approach, when the main emphasis is given to synchronizer duty, a new transmission concept, known as the ‘M’ series, has been evolved, which brings with it some important advantages: saving of weight; faster synchronization, making for greater road safety; less space; lower manufacturing costs. The theoretical study compares the expected performance with that of a conventional five-speed synchronized transmission under identical conditions. Laboratory and road tests have established the validity of the theoretical appraisal.