The efficiency of a transmission (TE) can be defined as the
ratio between the energy transmitted to the wheels and the
energy provided by the engine at the crankshaft over an equal
reference time period or, alternatively, as the ratio between
the correspondent powers. Due to the losses (e.g. sliding
friction in the mechanical members in contact and viscous
friction for members submerged in lubricating oil), its value is
less than unity. The value of TE is influenced by many factors,
primarily the transmission architecture, that derives from
design choices (e.g. number of shafts, gears and electro-driven
frictions, number of teeth of each cogwheel, presence of
a torque converter, and presence of a hydrostatic section).