It has officially been 30 years since Audi brought their all wheel drive system (Quattro).
Jalopnik has a great article up about the history of Quattro and how it was developed. Here are some snippets:
That last bit is where things get interesting — it led to one of the most ingenious packaging solutions of the late 20th century. The Quattro’s longitudinal center diff is built into the back of the gearbox, and the gearbox’s primary shaft is essentially an extension of the crankshaft. The primary shaft drives a hollow secondary shaft, which then drives the diff. But here’s the cool part: A third, solid shaft lives inside the hollow secondary, transmitting power to the front axles. This is the much-lauded “shaft within a shaft” that everyone talks about, and it allowed the Quattro to pack a steamer trunk’s worth of components into a space barely larger than an overnight bag. (Note: Anyone who makes an Xzibit “Yo dawg, I herd you like all-wheel drive so I put a shaft in your shaft so you can diff while you diff” joke at this point will be shot.)
