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
The engineering and technology to do this has been around for decades. It’s only a thing today because the government has forced manufacturers into an almost unobtainable requirement to meet certain fleetwide MPG requirements aka CAFE. A 10 speed transmission keeps the engine RPMs lower throughout the speed range but essentially gets you to the same gear ratio as a 5 speed at normal highway speeds. This allows for a tiny bit of increase in fuel efficiency to satisfy government regulations.
Basically, with 5 gears, your RPMs might hit 3000 at the top of each shift point. With a 10 speed you may only hit 2300 RPMs at the top of each shift point. This reduces fuel consumption.
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