How many gears is too many?

Many new vehicles on sale today have 8 or 9 speed transmissions. Manufacturers are doing this in the name of fuel economy in order to meet the ever increasingly stringent fuel economy and emissions standards across the globe. However, I’m starting to wonder when will enough be enough. How many gears is too many?

A huge proportion of the new cars being sold in 2019 have the ZF 8-speed gearbox in it, including the new Toyota Supra, many BMWs, the Jeep Trackhawk and many others. The transmission behaves differently in the various applications only because each manufacturer is applying their own unique programming in its computer, otherwise it is an identical unit. In 2017 alone, there were over 3.5 million ZF 8-speed gearboxes sold. Many manufacturers are using the ZF 8-speed because it’s a great mix of packaging size, cost and the performance is not far off of what you would get in a dual clutch gearbox.

The 2019 Ford Mustang is being offered with a 10 speed auto, replacing the outgoing 6 speed unit offered previously, and is available with both the Ecoboost 4 cylinder and the V8 GT models. The transmission was jointly created between Ford and General Motors and has a wide application across both manufacturer’s platforms including the Ford F-150, Expedition, various Lincoln models, Chevy Silverado, Camaro SS, Tahoe and more. The transmission may be great at keeping the vehicles in the ideal torque range but the trade-off is that it shifts. A lot.

The constant shifting and transmissions generally not being as responsive as consumers are expecting in vehicles with large numbers of gears is a common complaint from end users. The constant shifting is from the vehicle ensuring that it is using the optimal gear for the what is being asked of it and may be technically superior but can create a sense of frustration of drivers.

Now with some vehicles being offered with an 11-speed gearbox, it seems like there isn’t any more benefit to putting more gears into a transmission. There must be a balance between keeping revs low and generating enough torque to propel the vehicle forward in an acceptable way.

One option would be to engineer the torque curve so more torque is available at a lower rpm. This is exactly what Mazda has done with their new SkyActiv-G engine where all 310 lb-ft of torque is available at just 2000 rpm. With an engine that produces a lot of torque all through the rev range , less emphasis needs to be put onto the transmission to drive ensure optimal torque for the driving situation. While the engine and transmission do need to work together, the less pressure put on the transmission to create an optimal torque curve allows engineers to focus on fuel economy and performance instead.

I don’t see any additional gears coming any time soon to automatic transmissions. Enthusiasts who want manual transmissions for the driver engagement, but it’s hard to deny that an automatic transmission is technically superior. The next decade will be interesting to see what happens with gearboxes, especially with the rise of electric vehicles (EVs) as EVs typically only have a 1 or 2 speed transmission, or no transmission at all.

How many gears is too many? Let me know what you think in the comments below.