LEO LIMON [8-10 / 0º-30º], one of the constellations in the "One Size Fits All" (1975) "universe", has a star named "Differential". A differential distributes power from car transmission shaft to a pair of Left-Right wheels (1st functional requirement) while allowing wheels to rotate at different speeds (2nd functional requirement).
The differential was first invented in China, in the third century, A.D. Why use a differential?: When a car turns a corner, one wheel is on the "inside" of a turning arc, and the other wheel is on the "outside". Consequently, the outside wheel has to turn faster than the inside one in order to cover the greater distance in the same amount of time. Thus, because the two wheels are not driven with the same speed, a differential is necessary. A car differential is placed halfway between the driving wheels, on either the front, rear, or both axes (depending on whether it’s a front-, rear-, or 4-wheel-drive car). In rear-wheel drive cars, the differential converts rotational motion of the transmission shaft which lies parallel to the car’s motion to rotational motion of the half-shafts (on the ends of which are the wheels), which lie perpendicular to the car’s motion.
See also: Cars (CC).