MECANISMO DE SELECAO DA RAZAO DE ENGRENAGENS PARA USO COM UM CONJUNTO DE TRANSMISSAO E APERFEICOAMENTO EM UM CONJUNTO DE TRANSMISSAO

A transmission range selection mechanism for use with a vehicle transmission assembly having a main gear box and an auxiliary, two-speed gear box provides control over both with a single shift lever moved through a conventional shift pattern. The shift lever is pivotally mounted to a transversely disposed shift rail which is translatable between a first and a second position. A two-position sensor is coupled to the shift rail such that one output state is generated when the shift rail is in the first position and the second output state is generated in the second position. The two-position sensor controls selection of the two gear ranges provided by the auxiliary gear box. Three main shift rails are disposed in a conventional, parallel array at right angles to the auxiliary shift rail and include three shift yokes. The outer two shift yokes include spring-biased pins disposed within shift lever receiving slots. The spring rate of the spring-biased pins is such that the shift lever functions as a second class lever to translate the auxiliary shift rail between first and second positions thus commanding corresponding shifts of the auxiliary gear box while the shift lever is engaged within the center shift yoke. Gear sets and thus gear ratios associated with the center shift rail and therefore utilized twice, when the auxiliary gear box is in both its low and its high drive ratio, thus providing additional gear ratios in a conventional, though extended, shift pattern.