How Automatic Transmissions Overtook Manuals in Speed and Efficiency


For ages, manual transmissions were the best way to control the shifting in cars, but recent advances have made the automatic dominant.

Manual transmissions are, unfortunately, become a dying a breed in the US, but let’s look at why.

Automatic transmissions were invented by GM in the 1930s, but for the most part, they were sluggish and rudimentary. On a commercial scale, automatics weren’t implemented until after the second world war. Even though automatics decreased the amount of work a driver needed to do, cars equipped with these “slush boxes” were slower and less fuel efficient. Manual transmissions could beat out an automatic any day. This was mostly due to how torque is converted in each type of transmission. In manuals, nearly 100 percent of the torque from an engine is translated directly into wheel rotation. Early automatic transmissions, on the other hand, used a hydraulically operated converter with a pump and a turbine.

The hydraulically operated automatic transmission is exactly why for ages, it could never achieve the same level of efficiency as automatics. As a car’s engine speeds up, the fluid slippage increases, beginning to spin the turbine. The turbine rotating drives the wheels, and as slippage varies, the automatic transmission shifts gears. Since there is no direct connection between the transmission pump and the turbine, efficiency in early automatics was less than 80 percent.

However, in the last 15 years, engineers have made significant advances in automatic technologies. Automatics are now as good or better than their manual counterparts. Modern automatic transmissions can now achieve 100 percent torque conversion, like manuals, through the implementation of three devices: increased gear ratios, electronic controls, and lock-up torque converters. There are now automatics with 8 to 9 gears, which enable a car’s engine to operate around a highly efficient 1500 RPM at all speeds. Electronic controls also enable the computer-driven system to shift gears at the specific time indicated by the engine. Typically, these systems interface with engine controls and can, more accurately than human drivers, tell when a transmission needs to shift. These electronic controls all feed into lock-up torque converters which establish a mechanical connection inside of automatic transmissions. These lock-up converters mechanically interface between the pump and the turbine in automatics to achieve the same level of efficiency as manuals. With all of these advances combined, automatics are now just as good or better than manuals.

800px-transmission_arrangements_of_a_six-wheeled_vehicle_manual_of_driving_and_maintenanceOnly 3.1% of all cars sold in the US are equipped with manual transmissions now, and American teens simply aren’t learning to drive manual. Automatics are also better for off-roading due to the hectic nature of the driving, as well as being superior for large trucking industries. Humans can be fairly precise when it comes to manual shifting, but computer-driven interfaces win out every time.

Now, you may say, “everyday cars now have automatics because they’re easy, but supercars would never switch from manuals,” but that statement would be wrong.  You cannot buy a new Lamborghini, Ferrari or McLaren road car equipped with a manual transmission. It’s impossible. That is also bolstered by the fact that Mercedes, Range Rover, and Lexus all make automatic 7 to 8, or even 9, speed transmissions that far outperform their manual counterparts. Even cars designed for luxury and speed are switching to automatic. Technology is simply beating out old mechanical human interface.


So, how then did automatic transmissions overtake manuals? Well, through the incorporation of innovative engineering and lightning speed digital processing, automatic transmissions have better reaction and timing than humans ever could. This means a computer can always outperform your shifting and maximize fuel efficiency and speed, perfectly in tune with the ability of the engine.

Sources: Daily Nation, FIX & Autoblog

Images: [1], [2]

Profile photo of Trevor English
Trevor is a civil engineer by trade and an accomplished internet blogger with a passion for inspiring everyone with new and exciting technologies. He is also a published children’s book author whose most recent book, ZOOM Go the Vehicles, is aimed at inspiring young kids to have an interest in engineering.


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