Abstract: This invention provides an improved automotive transmission, particularly for highway trucks, wherein an overdrive condition of the transmission may be obtained by extension of the normal H-shaped shifting pattern of the gear shift lever. A direct drive condition of the transmission is obtained when the gear shift lever is in the forward position of the last lateral leg of an extended H shift pattern and the overdrive condition is obtained when the gear shift lever is in the rearward position of such last leg of the shifting pattern, thus requiring no unusual shifting movements on the part of the operator to effect the conversion of the transmission into the overdrive condition.

Abstract: A transmission interlock for use in a motor vehicle transmission having at least two gear ratio selection means in tandem within a common housing. The transmission interlock includes an auxiliary shift rail parallel to and spaced from two operative shift rails which it interlocks. The auxiliary shift rail is linked to one of the two shift rails and translates positively therewith. An interlock member transversely disposed between the auxiliary shift rail and the second of the two shift rails interacts with slots or blind apertures in the shift rails to prevent selection of certain combinations of shift rail positions corresponding to prohibited gear ratio combinations.