Basically, we’re talking witchcraft. When it comes to the modern automobile, even the casual observer can relate how most systems work: gas goes boom – the engine turns; brakes clamp down – the car comes to a stop; turn the steering – front wheels pivot. But as for the device marked PRND? That thing’s gotta be made in Hogwarts.
Science fiction writer Arthur C. Clarke once famously observed, “Any sufficiently advanced technology is indistinguishable from magic.” But if it’s magic, why are most enthusiasts so quick to deride the modern automatic transmission? After all, it’s far and away the most popular choice and opens up whole new worlds of driving. It’s easier to live with in stop-and-go traffic, you can enjoy your coffee without having to scrabble for the shifter, and it surely holds particular appeal to members of the buccaneer community. Arr, it be quite taxin’ te operate a clutch with me peg leg, Jim lad.
Leaving aside automated manuals such as Porsche’s PDK, and pulley-based systems like the continuously variable transmission (CVT), here’s a brief overview of the history of the modern auto-box. Wands at the ready, Potters and Grangers, let’s begin.
Slushy beginnings
Just who came up with the first automatic transmission is as muddled a tale as who invented the automobile (and don’t necessarily believe claims that Mercedes-Benz did the latter). At the turn of the century, all kinds of inventors were fiddling around with unusual ways to get their horseless carriages to trot at different speeds.
Also read: In defence of CVTs — they’re actually not as bad as you’ve heard
Frenchmen Louis-Rene Panhard and Emile Levassor must be awarded the distinction of coming up with the first proper transmission, demonstrated in 1894. And by “demonstrated,” I mean, “it broke.” The theory was there, and the demo car was soon working again, but it rather ignominiously gave up the ghost before the assembled press corps, and Panhard and Levassor were reduced to lecturing in front of a chalkboard. “More hocus-pocus from charlatans!” the papers cried.
Next, the Sturtevant brothers of Boston, Mass., managed to work out a two-speed automatic transmission based on centrifugal weights. Essentially, this relied on the speed of the engine to activate a series of weights, that, um, would deactivate a clutch and … OK, look: even after reading up on this thing, I have no idea how it works, except to say that it mostly didn’t. It too broke down with sad regularity, bringing a literal interpretation to the shiftless transmission.
Canada can take some small pride in our own automatic pioneer, Alfred Horner Munro of Regina. Munro was a steam engineer – and if you lived in Regina in the early 1920s, you might as well be involved in a career that involves huddling up close to a boiler. His patent for a compressed-air based transmission dates back to 1921, earning him at the very least a footnote in the history books. However, his invention didn’t really find a commercial foothold.
Instead, it would be a pair of Brazilians, José Braz Araripe and Fernando Lehly Lemos, that would reportedly come up with the idea of using hydraulic pressure to handle the shifts. Their idea and prototypes would find favour at General Motors, already at work on the automatic. Finally, 75 years ago, a recognizable ancestor of the modern automatic transmission would debut. It was called the Hydra-matic, and it was soon gearing up for war.
Chrysler 727 Torqueflite automatic transmission
Clayton Seams, Driving
Hail Hydra!
All modern automatic transmissions (except dual-clutch and CVTs, as mentioned) utilize some form of the Hydra-matic’s two central features: a hydraulic coupling and a planetary gearset. We’ll come back to those, but first, some tanks and a company president’s ho-hum driving skills.
The name of Alfred P. Sloan, president of General Motors, lives on today not just in company history, but in the works of his eponymous foundation. You might recognize it from mentions in the credits of NPR’s excellent science and technology podcast, Radiolab.
As an executive and philanthropist, Sloan was exemplary. As a driver – not so much. Mind you, the transmissions of those early years were much more complicated to drive than today’s modern machinery, so some leeway must be given. Seeking a solution that would make driving more accessible to the general public (and thus sell more cars, naturally), Sloan continually spurred his R&D division to chase down a truly clutchless transmission. After an unsuccessful launch of an optional semi-automatic option in the Buick lineup called the Automatic Safety Transmission, the team had figured out a way to go from three pedals to two.
An image advertising GM’s Fully Automatic Transmission (Hyrdamatic) from 1940.
Handout, GM Archives
The Hydra-matic was first offered as an option on Oldsmobiles only in the 1940 model year, at a cost of $57. The units were constructed at the Detroit Transmission division, and had four forward speeds and one reverse. There was no Park setting initially – the driver simply selected reverse and then shut the car off.
The Hydra-matic proved very popular, and sold something like 200,000 copies in its first run. However, there was what you might call a bit of a fuss occurring in Europe at the time, thanks to a small shouty man with a silly moustache and a failed career as a painter. GM had been preparing to convert from building passenger cars to producing war material for some time, and as the U.S. entered the European theatre of the Second World War, it elected to use its Hydra-matic transmissions in tanks. Notably, the M-5 Stuart had twin Cadillac V8s and twin Hydra-matic transmissions, one for each tread.
By the time the war had ended, many of the early quirks of the Hydra-matic had been ironed out – GM marketed their transmissions as “battle-hardened” — and the booming post-war economy was ripe for large, luxurious vehicles with easy-to-drive transmissions. Hydra-matic lead the way, and other manufacturers were forced to follow: Packard with Ultramatic, Ford with the Ford-o-matic, Chrysler with Powerflite and Torqueflite, and so on. Curiously, early Lincolns actually bought its transmissions from GM, as the Hydra-matic was the only thing strong enough to handle the V8 power.
By the middle of the 1950s, the automatic transmission was ascendant in the North American market, and would continue to grow in popularity right through to the modern day. So how do they work, exactly?
Major controls are conveniently located on the centre console.
Russell Purcell, Driving
The modern monster
For dissection, let’s select something interesting, and in keeping with the historical precedent of the Hydra-matic: the just-released Corvette Z06. Here are the quick specs: a supercharged 6.2L V8 cranking out 650 horsepower and 650 lb.-ft. of torque, a curb weight of just under 1,600 kg, and a sprint to 100 km/h in 2.95 seconds, thanks to a new available eight-speed automatic transmission.
If the Hydra-matic cut its teeth taking the fight to Panzer divisions, then here’s its descendant doing pretty much the same thing. GM’s new heavy-duty 8L90E is claimed to shift even faster than Porsche’s doppelkupplung dual-clutch gearbox, and will go toe-to-toe with Germany’s best down the quarter-mile.
Slice open the silvery box inside America’s supercar-fighter, and you’ll find some extremely complicated workings. Yes, there are eight gear ratios to choose from, but they don’t operate like the sliding selectable gears in a manual transmission. Instead, the automatic works via a planetary gearset, attached to the engine via a torque converter.
The 2015 Corvette Z06 will start at $78,995 in the U.S. and $85,095 in Canada.
Handout, GM
GM’s official press release on the 8L90E is filled with phrases like, “Clutch compensators are fed by lubrication oil rather than the dedicated and regulated feed design of the 6L80.” That’s, um, good? I guess?
Let’s keep it simple. GM’s new box has all sorts of engineering innovations to speed up and smooth out shifting, but the essential architecture is still there. Its torque converter is more compact, uses synthetic fluids, and has a next-generation controller, yet it is still based on the same principle: just as a clutch must be let out gradually for smooth engagement with manual transmission, the viscous nature of fluid can be used to transfer power gently between the spinning input shaft of the engine, and the output shaft that drives the wheels.
In the gearbox itself are the planetary gears, comprised of an outer ring gear, a central sun gear, and the planet gears that spin between them. Most modern automatics have two full planetary sets in their casing, and the key thing to note here is that the gears are constantly meshed. Unlike a manual transmission, where you’re actually sliding into a new gear, an automatic’s planetary gearset is always linked, and it’s the action of clutches to clamp different gears in a stationary position that produces the ratios. The more gear ratios a transmission produces, the more complex the internal workings.
The Manual’s Last Stand
Compared to the seven-speed manual version, the automatic Corvette Z06 will provide better fuel economy thanks to quicker shifting and longer final gearing, better acceleration, and a more tractable driving experience in heavy traffic. You’ll also be able to keep both hands on the wheel when unleashing 650 hp on the track – this is no bad thing.
The short throw six-speed manual transmission in the Dodge Dart felt very refined, and rowing through the gears was a smooth operation.
Russell Purcell, Driving
From a maintenance perspective, the greater complexity of an automatic requires more servicing than a manual, and replacing a single clutch is much less expensive than a full automatic transmission rebuild. However, as most cars sell equipped with automatics, that’s where the research and development dollars primarily go. There’s little to recommend the manual these days except for the feel and the experience of the thing. Even though I objectively know that the eight-speed ‘Vette will be faster, the stick-shift version will probably be a little more fun.
However, we’ve come a long, long way from those early Oldsmobiles. It might be witchcraft, but these days we’re not about to burn a car at the stake for having an automatic transmission, not when it goes like a Quidditch broomstick but still leaves a hand free for the morning double-double.
