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
1) Presision of automatic tools. It allows to make finetuned details with almost perfect fit (it can be made perfect and you can find gifs of so fine made details that they look like solid one when connected. However machinery **needs** to be almost perfect)
2) better metal production. That allows to make sturdy details smaller in size.
In the end of the day automatic transmission has more than 200 details. 50 years ago it would take 5x volume to be placed and 10x weight.
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