Commentary: Considering The Automatic Transmission

ZF 9-speed Automatic FWD application
This is sexy – ZF's nine-speed automatic for front-drive-biased applications. Photo by Randy Stern

We take transmissions for granted.

It is true. We do not think of transmissions as we do engines, tires, infotainment systems…and so forth. When we depress a clutch, shift a gear or let the automatic work for itself, we often do care what it does other than facilitate the engine's performance to the drive wheels. Or, do we even think in those terms?

I appreciate transmissions. No, seriously, I do. Though I am physiologically challenged to engage a manual gearbox via a clutch pedal, I respect what they do. I absolutely care when they add some form of electronic doo-dad to enhance engine response to both up- and downshifts. It is not natural to the purist.

Therefore, I focus on clutch-less gearboxes. Notice I did not just say "automatics." The whole host of clutch-free transmissions land onto this category, from efficient dual-clutch boxes to full slush-o-matics. The question I pose upon each one is whether they do the job translating a gear change to the engine's revs and how it converts performance onto velocity.

Transmissions may not be a sexy topic of discussion, but they are. At the North American International Auto Show, I stopped the ZF booth to get a closer look at their new eight- and nine-speed automatics. Built for rear-drive-biased vehicles, the new eight-speed automatic has been placed on a few key Chrysler products – including the Ram 1500 pickup. Soon, this eight-speeder will make it way throughout the 2014 Jeep Grand Cherokee lineup.

A few feet away was ZF's latest creation: A nine-speed automatic made for front-wheel-drive-biased applications. It is rumored that the new nine-speeder will appear on some of Chrysler's newer CUS-Wide products and, possibly, the Dodge Dart. Admittedly, I like the gearbox's design and some of the torque response and sensing technology onboard of the new gearbox.

The mind boggles at nine speeds, let alone eight. Now I ask, "How have we lived through the evolution of the automatic gearbox by the addition of more ratios?"

When I began driving, three gears was the standard for automatics. You had "drive," which was the most direct ratio of all gears. That gear matched engine revs perfectly and assured proper propulsion at the bane of fuel economy. You had "low" to start off with – and for necessary traction on bad surfaces. Then, you had that second gear. Sometimes, you could start in second when the occasion deemed it necessary.

Things were much simpler then. Nowadays, it is not just how many ratios are in a gearbox, but how they are delivered. We have dual-clutch set-ups, single-clutch robotic manuals and continuously variable transmissions. How could anyone keep track of what it out there?

Maybe I could help. After some consideration, I began to wonder, "what if I created an automatic transmission. How would that work?" Considering I am not an engineer, and perhaps, this may be out there on the road, I figured I would give it a shot.

After all, I have been driving automatics all of driving life. I should know how a "perfect" one could be configured, if given the engineering gene.

PRIMARY GEARS: If there is a heart to a transmission, it would a series of three to four ratios working the hardest of them all. Just as you see in the older automatics, there are core gears performing at certain ratios for specific functions. The lowest gear is where you start the vehicle in normal conditions. The top gear of this set is a direct ratio working to match revs from the engine for optimal passing and transitional performance. The middle gear(s) of this set act as transitions between the lowest and highest gears. These gears work well in urban driving.

"PERFORMANCE" GEAR: There would be one gear set aside for a specific ratio to induce the quickest response from the throttle. In passing situations or highway merging, this gear would trigger a higher rev level from the engine and necessary traction onto the drive wheels in these situations. It also smart enough to sense a gear transition when the maneuver is accomplished. Where this would reside would be within the primary gear set, to work better within the key ratios within gear transitions to and from this specific ratio.

OVERDRIVE GEARS: In theory, overdrive is a sub-direct ratio designed to relax the engine. With six-to-nine gears being put on an automatic, one had to question how many overdrives one needs to ensure leisurely cruising at high speeds. I would suggest you actually need two. The first overdrive kicks down at about 40MPH where suburban boulevards have long stretches between lights or county trunk highways may not be ideal for travel. In all, this will save engine revs at these speeds, but provide enough traction response to the drive wheels.

A second overdrive would kick in at highway speeds. This higher gear functions not only to save even more revs to relax engine performance. The trick to this second overdrive is sensing when the vehicle is driven at the same speed over a long period of time and distance. It relaxes both the engine and transmission, until a change in throttle response or braking is read by the gearbox's brain.

"WINTER" GEARS: In the old days, one had to start the car in a different gear than usual. Perhaps a set of ratios would work to help ease the pain of winter starts and traction issues. One gear would be specifically designed for exactly that – a ratio where it would induce proper winter starts and initial drive-offs for the purpose of facilitating engine warm-ups and a proper flow of the air-fuel mixture avoiding condensation. The "warm-up" gear would help in creating better fluid transfer within the gearbox as well. A second gear would help in constant traction assist providing the right amount of torque between the engine, the transfer case or center differential and the drive wheels. This gear would work better with electronic four- and all-wheel drive systems with either terrain control or no human interaction.

BRAINS BEHIND THE BEAUTY: For years, the latest transmission technology are backed by a computer that sets the algorithms for shift points to match certain revs. With some vehicles offering "driver modes," transmission computers now have to think in terms multiple settings that are switchable on the fly at any second. However, for certain gears to be engaged, additional algorithms will have to be programmed for the Performance, Winter and multiple Overdrive ratios to work on those specific instances when needed.

Trucks should not be ignored from this equation. When you engage a Tow mode, specific transmission algorithms are set to enable the maximum amount of torque to pull a capacity over the actual curb weight of the vehicle. Some of the proposed gears would come into play, but shift points and rev-matching needs to be adjusted to enable full towing power under load.

The last consideration regarding transmission management is fuel economy. The consumption gap between an automatic and a manual has been equaled, if not tipped to favor a clutch-less gearbox. You could point to the computer for doing so, but the development of multiple overdrive gears and developing algorithms that enable engine efficiency are mostly credited for this change in positive fuel consumption for automatics in the past decade or so.

But, why would I look at a multi-gear conventional automatic to examine what would be its future? Consider that I did not focus on a CVT here. Nor was there any consideration to a robotized single-clutch manual or a dual-clutch gearbox. By creating the eight- and nine-speeders for this decade’s worth of vehicles, ZF made it clear that the good ol' automatic gearbox still has a place in our driving world. They are simply making them better.

For this automotive writer, that is indeed a good thing.

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