How come we can’t just add X amount of gears to a transmission and have one of the most efficient cars ever?
In: 95
That’s exactly what we did! In 1950 Chevy came out with the first automatic transmission, the power glide! It had 2 gears and that was it, low and high. It wasn’t very efficient but it was ground breaking as a car could finally shift itself.
Then in 1969 Chevy came out with the Turbo 350 transmission. It had 3 gears closing the gap between low and high. It made the cars more fuel efficient and improved performance. In fact Turbo 350’s and Turbo 400’s (a beefier version of the 350) are still used for drag racing. They are the best transmissions for holding BIG power when upgrades. A fully upgraded Turbo 400 can handle 4,000+ horsepower. Crazy for something designed in 1969.
After that we get the 700r4. It was still an old school transmission but they added a 4th gear. This is an overdrive gear which is great for fuel mileage. It’s not designed for you to accelerate in, just drop the RPMS for better mileage. So once you hit 70mph and stopped accelerating and began to cruise, it would shift into 4th to get better mileage. This transmission gave way to the 4L60E & the 4L80E. The 4L60E is a 4 speed like the 700r4 except it’s electronically controlled. The 4L80E is just a beefier 4L60E like the turbo 400 is a beefier turbo 350.
In the ever increasing battle for better mileage in 2005 Chevy came out with the 6L80E. This is similar to the 4L80E but it has 6 gears instead of 4. Then in 2017 GM stepped it up again and made the 10L80E. A 10 speed transmission designed for high end sports cars.
Now it’s important to note WHY having more gears increases efficiency and why adding more gears isn’t always the right answer. The more gears you add, you suffer from diminishing returns in the area of efficiency. It also makes the transmissions significantly more expensive and complex. To be truthful the 10 speed is probably the most gears they will ever do and even then it’s a bit of a gimmick.
Ignoring the engine on the planet is going to have a spot in the RPM range where it is operating at its highest level of efficiency. It’s going to be fairly narrow just a few hundred RPMS.
So to get more efficient cars we want to keep them in that range while accelerating and cruising. By adding more gears you can maximize the amount of time you spend in that RPM range. If you have a 3 speed your range of RPMS range while accelerating may be from 1,500 to 3,500 RPMS. That’s a 2,000 RPM range, much larger than the efficiency range of the engine. If you have a 10 speed you may be able to keep the RPM range between 2,000 and 2,500 RPMS, a 500 RPM difference and definitely keeping you in the engines efficiency range. As you add more gears that range gets smaller and smaller. It doesn’t really improve efficiency because it’s still sitting in the efficiency range of the engine either way.
To get more efficiency you have to look at other ways. Things like better aerodynamics, less weight, and less friction.
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