(…and Car Dealers Don’t Even Know What it is)
The Power Train
The Transmission is a very important part of most cars. Transmissions have to handle tremendous power (even in a small car). They are very subject to wear and failure, and they are typically in a really bad spot, which makes them very expensive to service (and worse to replace).
Today, there are many types of transmissions: A/T, M/T, CVT, DCT, and lots more. Just as bad, different companies use different names for what are basically the same thing: Vacamatic, Power Glide, TorqueFlite, Hydramatic. What does all this mean? Which is better?
It turns out that even Car Dealers are sometimes clueless when it comes to that mysterious thing they call a “Gear Box” overseas.
Here’s a clipping of an web page I recently came across:
I want to clarify that I did not change the layout. These 2 cars were advertised right next to each other. Yes, It’s 2 different locations, but it is 2 lots of the same dealership, and both cars are 2023 Corvette C8’s, but they list 2 different transmissions (circled in the above picture).
The problem is that the 2020-2023 Corvette C8 only came with one transmission. – And neither “Automatic” nor “8-Speed” is really the best description of the transmission that is in those cars.
Both show “6.2L V-8 Engine”, which is in fact correct. So what is it about the lowly Transmission (literally one of the lowest points in the car) that causes a dealer selling $88,000 cars to not even know what transmission it has?
So what is a transmission? Why do we need it in our cars? and Which type is the least evil?
I want to clarify that what is described here only applies to “normal” Gasoline or Diesel cars. Electric or Hybrid cars can have various other arrangements, or in some cases no transmission at all. For example, some years of the Toyota Prius had a transmission that mechanically only had a 5th gear.
Internal Combustion Engines (ICE) can’t produce power (torque) at a wide range of engine speed (RPM). For best fuel economy, the engine must run at it’s “happy place” regardless of the speed the car is moving at. But it gets worse – an engine has a certain speed where it produces the most power, and that’s different than the speed where it gets the best economy – Hence the need for a “Passing Gear”.
So that’s the job of the transmission – Letting the engine do it’s best whether we are cruising down the highway, Going through a school speed zone, or towing a 12,000 pound boat up the side of a mountain.
The Automatic
Here in the “Stick-Adverse” USA, the most common transmission is what we call the “Automatic” – Although we will see that this is becoming a bit more complicated today. The classic automatic transmission uses a torque converter and planetary gears to provide (typically) 2 to 8 speeds (gear ratios). This kind of transmission has been the “normal” type in American cars (and most cars driven in North America) for nearly 75 years. It’s also “evil” in that it steals power and fuel economy.
They also have parts in them that are designed to wear out, and are very hard to replace. The torque converter wastes power (slips). And it slips the most just when the engine is already using the most fuel – During acceleration. The inside of the transmission also slips (or maybe in this case, I should say that they “drag”) – a lot of it in the name of making smooth – barely noticeable – shifts. Make no mistake about it: Automatic transmissions do shift gears – they just do the shifting for us, and sometimes so smoothly we don’t notice.
The other problem is that they can’t possibly know what is going to happen next. Even the ones with modern electronic controls can’t know that the guy in front of you that has been doing exactly 3 mph for 2 blocks finally found his street and is going to turn off. They can’t see that the truck that is just off your rear quarter panel is drifting into your lane on the highway, and you need to get out of there. They can only react. Some react pretty well – others – Not so much.
The Manual
Before the automatic matured enough to become popular, and even in the decades since, The classic manual transmission and dry clutch was the only other choice. 3 pedals intimidate some 2-legged drivers, and the driver must not only select the right gear, but also do the job of that torque converter – slipping the engine power when starting off or between shifts.
The main advantages of the manual is that (assuming a skilled driver) there are fewer and shorter times when the clutch is slipping. There is also much less drag and power lost in the transmission itself (almost none – manual transmissions do not typically need cooling because they don’t waste energy as heat). Historically, manual transmission cars used to get several Miles Per Gallon (MPG) more than an otherwise identical car with a classic automatic transmission. It’s still a pain to change a clutch, but easier (read: cheaper) than changing bands and other wear components in a classic automatic. Most manual transmissions will last the life of the car without service other than the clutch.
A smart driver can also downshift before stepping on the gas to pass, or can make the decision to stay in a lower gear (avoid a shift) because they can see that the traffic in front of them is not clearing.
The Heck with the Laws of Physics. I want Automatic Shifting, Great Fuel Economy and Fewer Repairs!
OK – No problem. Enter the DCT. While the concept of the Dual Clutch Transmission has been around for decades, modern electronic controls are making them practical in many of today’s cars. Essentially a DCT is two (or even 3) Manual (that’s right – I said Manual!) transmissions in one unit — each with it’s own clutch. The trick here is that the “Manual” transmissions are Automatically shifted by a computer, and that same computer operates the clutches. Smooth shifting is done by a simple trick – One of the manual transmissions has the odd gears, and the other has the even gears. Want to shift from 1st to 2nd? The computer pre-shifts the even gear box into 2nd, and when it’s time to shift, it engages the even clutch while simultaneously and perfectly disengaging the odd clutch.
The result? Smooth shifts that are faster and cause less clutch wear than any 2 legged race car driver ever could. There’s no torque converter, and no “bands”, so there’s almost no slippage and almost no drag, so DCT cars typically get better fuel economy than similar cars with either an automatic transmission or manual.
But what about the drivers ability to predict the need to shift? Well – Since a DCT is essentially a manual transmission, most (or all) can be put in a manual mode. The driver simply operates a shift up or shift down paddle behind the steering wheel, and the computer operates the gears and clutches for a fast, perfect shift.
Also DCT is the correct answer to the Dealers confusion mentioned above. All of the new Corvettes (Corvette C8’s) have the Tremec 8 Speed DCT. I’ve driven them in both Automatic and Manual mode, and I got out of the car with a smile on my Cynical face. Nothing with a torque converter will do that.
What’s more Evil than Evil?
The CVT. –No wait, I’m just introducing the next type of transmission, not answering the heading – Well, maybe I am. The Continuously Variable Transmission is an attempt to get rid of shifting all together. It’s essentially 2 cones next to each other, and pointed in opposite directions. A belt slides along these 2 cones, thus providing a continuous range of ratios.
And CVT’s do that. They actually work pretty well on something like a moped where there’s not a whole lot of power. Now in actual modern cars, there are different and more complex arrangements of cones or vaguely cone shaped parts, but simple cones illustrate the basic idea. The problem is that no one has made one that can reliably and economically work in more powerful cars. There’s still friction (drag) and slippage, and some still rely on that evil torque converter – Evil with a shaft connecting it to evil.
In this Cynic’s opinions, CVT’s have all of the bad features of the Classic Automatic, and no benefit other than perhaps the super smooth transition from stopped to full speed.
My 250cc Honda Helix Scooter had a CVT, and I wouldn’t want a CVT in anything bigger than that.
But What About the….
Yeah, OK – There’s lots of other ideas that have been tried over the years. Citroen and Volkswagen (and others) tried to make manual gear boxes more “User Friendly”. Citroen had a manual 4 speed transmission where the clutch was automatically operated by the central hydraulic system. When it was adjusted right, you got that perfect clutch operation of the DCT, and all the driver had to do was select the desired gear. In the Volkswagen system, the diver operated the clutch by pressing down on the shift lever. No real advantage, but at least the feet and pedals equation balanced. How ’bout using a massive propeller to drive your car. Then you don’t need a transmission at all. Of course, it’s not exactly pedestrian-friendly.
Conclusion
If you don’t want to deal with a plain old manual “stick shift” car, the DCT is your best bet. Even if you are into “Spirited Driving” you may find that “Flappy Paddle” shifting is even more fun than grinding gears in a conventional 4-6 speed manual. Even if a base model car comes with an old style (and inefficient) automatic transmission, the same car may be available with a DCT as an option. Ask your car salesman “What transmissions are available for this car?”
