This is part of the reason why four speed autos stayed in use for so damn long. You can automatically shift a four speed transmission with a pair of solenoids that turn on/off based on the input values from a couple of basic sensors.
The solenoids control which pair of clutches in the transmission engage, which in turn, determines the gear the transmission is in.
Driveability wise, they were awful, and their overall efficiency was pretty bad. But the fact that it could automatically select the correct gear out of three or four with just one user input (throttle) is still marvelous.
They could also handle insane amounts of power for the era. The GM 3L series came out in 1964 and was the transmission people would reach for when they were putting WWII era plane engines into crazy automobiles.
50 years ago that was true. Sometime ago though (I don't know when, but I'd guess starting in the 1990s) they changed to electronic computers. Using electronics makes some things simpler and puts the complex parts in standard hardware (a CPU is much more complex but it isn't custom designed for you), or software (easy to change if you get it wrong.
For the fuel injection and ignition (spark) timing yes, but the camshafts to open and close the valves are still driven by a gear, belt or chain. Even variable valve timing is mostly controled by mechanical or hydraulic means, though I'm guessing some electronics may be involved.
Yeah, but the electronic control in 4 speeds was basically replicating the mechanical control of the previous generation. So it was more of an incremental improvement over old tech.
Whereas modern 6+ speed transmissions are very different in design and control.
