High efficiency gear transmission

A mechanical transmission comprising a speed change gearing shiftable under load, the speed change gearing having input means, output means and mechanical speed shift torque transmissible means interconnecting the input and output means, the speed shift torque transmissible means being selectively disengageable to provide a slip mode of operation between the input means and the output means, and a main synchronization means, the speed shift torque transmissible means including a mechanical wear component, the mechanical wear component being subject to increased wear during the slip mode of operation, the main synchronization means including a primary part drivable by an engine output shaft and a secondary part drivingly engaging the speed change gearing input means, mechanical main torque transmissible means interconnecting the primary and secondary parts, the main torque transmissible means including a non-fluid torque coupling operable from a driving nonslip mode of operation wherein its transmissible torque is at least as great as the engine output load torque and shiftable to a slip mode of operation wherein reduced torque is transmitted from the primary part to the secondary part, the non-fluid torque coupling including a mechanical wear component subject to increased wear during the slip mode of operation, the wear component of the torque coupling being constructed to withstand greater wear than the wear component of the speed shift torque transmissible means, the main torque transmissible means uninterruptedly transmitting no less than a minimal torque between the primary part and the secondary part, the transmissible torque of the main torque transmissible means being less than the transmissible torque of the speed shift torque transmissible means, the main synchronization means providing the greatest proportion of synchronization work required for a shifting cycle when changing gear speeds, the remainder of such synchronization work being provided by the speed shift torque transmissible means so that reduced size speed shift torque transmissible means are employable thereby maximizing speed change gear efficiencies, the transmission further including means for automatically regulating the transmission whereby the non-fluid torque coupling is automatically shiftable from the nonslip mode to the slip mode during each speed change shift of the speed change gearing.