As automakers like General Motors start electrifying the powertrains in a greater share of their passenger vehicles, there’s little chance that the trend of adding more and more forward gear ratios to transmissions will continue, says GM Global Executive Director of Transmission Electrification Mike Anderson. During a recent interview with Autoline‘s John McElroy, the transmission electrification boss said that transmissions incorporating one or more electric motors will effectively negate the need for GM to go much further than its current ten-speed automatic transmission, developed in collaboration with Ford.
Transmissions like the one used by the 2017 Cadillac CT6 plug-in hybrid – an “electric variable transmission” incorporating three planetary gearsets, five clutches, and a pair of AC motors – will become more widespread in vehicles with internal combustion engines, Anderson suggests. Pure-electric vehicles, which have become a major focus of GM’s, have their own unique propulsion needs, and don’t necessarily even require transmissions at all.
The powertrain of the 2017 Cadillac CT6 plug-in hybrid.
Whether or not a given battery-electric vehicle has a transmission – and whether or not that transmission has more than one forward gear – has a lot to do with the power-to-weight ratio of the vehicle and the maximum rotating speed of the electric drive motor(s), Anderson says. “A lot of folks are showing that even with something that has a very large weight with a small power output, a two-speed is actually something that somebody might want, but you don’t need the kind of gearing that we have today” with a BEV, he says.
The 2017 Chevrolet Bolt EV has a single-speed automatic transmission, but provides more than enough thrust for daily use, with a 0-to-60-mph time somewhere around six-and-a-half seconds, and a top speed of around 90 mph.
In any event, electrified transmissions will likely continue to see more widespread use in vehicles with internal combustion engines, making further investment into inflating the number of gears in conventional planetary automatics pointless. The Ford/GM ten-speed automatic might just have the highest gear count we’ll ever see in a GM product.
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I was wondering when the Gear Wars was going to come to an end.
With the demise of the manual and 10 gears in an auto likely to become au de rigeur in 5 to 10 years, it looks like they’re laying there cards on the table and saying enough is enough.
Interesting write up.
I was thinking the other day about some of the advancements we’ve seen in the automotive world the last few decades, and transmissions, while easy to overlook, have certainly been a big one.
A 10 speed transmission has three planetary gearsets plus an overdrive gear. Each planetary gearset can only give three gears so 3 + 3 +3 + overdrive = 10 speed transmission. A 4 speed transmission is a 3 speed transmission with an overdrive gear.
The restriction on electric motors is the the maximum rpm you can get. A conventional electric motor like an AC washing machine motor will only spin to about 3500 rpm because of the weight of the armature with all the copper windings for the electromagnet. You can use permanent magnets but they are costly and limited in availability. The result is that most new electric vehicles have a gearbox and a mixture of permanent and electromagnets.
You are nit up to date on how an electric assisted transmission works. Look for many Chevy Volt documentaries, even at GM’s sites, and relearn how it works. The 5ET50 uses only one planetary and the traction motor is the main power output, which can move the Volt up to 99 MPH, enough for any highway traveling. The second motor has multiple functions, including engine starter and generator, but it can also alter the planetary ratio between the gas engine and the final axle output by electronic control. It does in less than five moving parts what a 10-speed does with over 400 parts! Fewer parts means longer life.
There is no RPM restriction in the GM designed transmission!
Based on what I’ve seen, 10 gears definitely is it, which is what I expected. From what I’ve seen, in the Ford trucks, it can be a bit too “shifty”, but the reviews I’ve seen thus far for the GM trucks do not appear to have that issue (different calibrations being the key difference, besides powertrain choices). Overall, it’ll be busy in the city due to the sheer number of gears.
Next step really is integrating motors in there – with the transmission still having gears, that way motor RPM stays manageable, keeping it more efficient.
I expected this type of article to be revealed. Modern engineers have realized the multiple benefits of an electric assisted transmission as many hybrids, including the Chevy Volt and Malibu, and the Cadillac ELR and CT6, have over the common hydro-mechanical transmissions which still hold over 300 parts. The twin motors can do the work of over half of the mechanical parts, and do it continuously (no shifts) , quietly, and reliably with much less wear, giving a longer life. The second benefit is energy recovery through “regeneration” as the motors become generators which take the energy from braking to recharge the battery, then supply it back when accelerating without consuming any fuel. This is why hybrids get over 40 MPG easily.
The third no-so-obvious benefit is that the electric motors can add their power to the gas engine and out accelerate a normal gas engine of the same or larger displacement. This is the main benefit that hybrid supercars offer.
It may not seen ideal for performance needs, but if the imports are adding hybrid technology to their supercars, and GM will produce a hybrid Corvette soon, the hybrid transmissions will take over and save millions of dollars for all customers in gas consumption and maintenance in the near future. Then the pure electrics (no gas engines at all) will become the next step.
“The 2017 Chevrolet Bolt EV has a single-speed automatic transmission..”. This is a single speed fixed gearbox transmission, not “automatic” because the gear never changes, either manually by the driver or “automatically”. Tesla uses this, too, so basically all pure EVs never need any speed changes and all use a single fixed gearbox transmission, like the gearbox in a electric hand tool.