When I first started driving in the 90s it seemed like the 4 and 5 speed transmission was the best, modern transmission you could get. They were relatively reliable, and had enough gears to make acceleration, and fuel economy good in my Honda CRX.
Today, I can buy a Honda Odyssey with a 9-speed automatic transmission standard, and 10-speed on the high end model.
**What has changed in transmission engineering, materials science, and technology to allow more gears in the gearbox?**
What are the potential downsides? E.g. is the typical 10-speed as reliable as the old standard 5-speed gearbox?
Edit: To be more clear, this is an ENGINEERING, MATERIALS SCIENCE, and TECHNOLOGY question. I understand the benefits of having more gears for ride quality, and fuel efficiency.
In: Engineering
> What are the downsides? Is the typical 10-speed as reliable as the old standard 5-speed gearbox?
There *are* downsides. It’s not all free – just worth doing.
– If you keep everything inside the transmission the same size, the transmission gets bigger and heavier. This can cause issues physically placing it in the vehicle – a model designed for a smaller transmission might be physically incapable of mounting a larger transmission. It also has impacts on total weight and weight distribution.
– If you make everything in the transmission smaller, you increase the risk of manufacturing defects and potentially reduce the overall reliability of certain parts – less material makes wear more impactful. You may also have to add *additional* parts and complexity to make it smaller, like how the [Ford-GM 10-speed](https://en.m.wikipedia.org/wiki/Ford%E2%80%93GM_10-speed_automatic_transmission) has a *triple*-clutch design. That’s more potential points of failure, and more things your engineers might get wrong too. These are offset by all the gains in reliability *elsewhere*.
– More parts is also always going to be more expensive. More material costs, more labour costs, more design costs, etc. Even if you can charge more, you generally need to pay for the cost of production *before* you actually get to selling the car – so you’ve got more money tied up in inventory. That’s a drawback for the companies.
– More gears closer together means more frequent gear changes, in exchange for your smoother acceleration. If your sports car offers a paddle shift, you need to find a balance between “not making the driver constantly shift” and “giving good acceleration”.
All of this is why the 10 speed isn’t universal yet. These are very real drawbacks – some markets don’t want overly frequent gear changes, sometimes the added cost is unacceptable, sometimes shrinking individual parts won’t work and sometimes making the transmission larger won’t either. Engineering is all about compromises and drawbacks, and 10-speeds aren’t free.
Latest Answers