Nowadays, the automotive industry have been received more attention to improve the transmission efficiency. Most of the researches have been concentrated on development and optimization on transmission actuators, shifting elements, bearings, lubricants or lightweight constructions. Due to the low load requirements and associated low efficiencies for transmissions in driving cycles the transmissions cause energy losses which cannot be neglected. Two main strategies can be followed up for the optimization of transmission efficiency. At first the efficiency benefit of transmissions through optimization of hardware components will be presented. The second possibility is the representation of an optimal thermal management especially at low temperatures. Warming-up the transmission oil or transmission components can increase the efficiency of transmissions significantly. Techniques like this become more important in the course of electrification of drivetrains and therefore decreased availability of heat. A simulation tool for calculation and minimization of power loss for manual and dual-clutch transmissions was developed at the Institute of Automotive Engineering and verified by measurements. The simulation tool calculates the total transmission efficiency as well as the losses of individual transmission components depending on various environmental conditions. In this chapter, the results in terms of increasing the efficiency of transmissions by optimization of hardware components will be presented. Furthermore, the effects of temperature distribution in the transmission as well as the potential of minimizing loss at low temperatures through thermal management will be illustrated. These considerations take different cycles, including representative customer use into account, based on experience with the so-called 3D method.