The inventor of the first automatic transmission was Alfred Horner Munro.
The first automatic transmission using hydraulic fluid was developed in 1932 by two Brazilian engineers, José Braz Araripe and Fernando Lehly Lemos.
The evolution towards mass-produced automatic transmissions continued with the 1933-1935 REO Motor Car Company Self-Shifter semi-automatic transmission, which automatically shifted between two forward gears in the "Forward" mode (or between two shorter gear ratios in the "Emergency low" mode).
Driver involvement was still required during normal driving, since standing starts required the driver to use the clutch pedal.
This was followed in 1937 by the Oldsmobile Automatic Safety Transmission.
Similar in operation to the REO Self-Shifter, the Automatic Safety Transmission shifted automatically between the two gear ratios available in the "Low" and "High" ranges and the clutch pedal was required for standing starts.
It used a planetary gearset.
The Chrysler Fluid Drive, introduced in 1939, was an optional addition to manual transmissions where a fluid coupling (similar to a torque-convertor, but without the torque multiplication) was added, to avoid the need to operate a manual clutch.
Overfilling an automatic transmission with too much transmission fluid causes the transmission to not circulate the transmission fluid properly and then can lead to overheating and other damage.
Too little fluid can also damage the transmission.
When you overfill an automatic transmission with too much transmission fluid you will cause damage to the automatic transmission which will overtime cause problems.
Overtime the transmission will have problems and then it will eventually go bad on you leaving you stranded.
Adding too much transmission fluid or overfilling your transmission can cause foaming and transmission fluid starvation for the transmission which is very damaging because when the transmission doesn't get the proper amount of transmission fluid the gears and bands are not lubricated properly.
This can cause the transmission to completely fail so if you do overfill the transmission fluid you need to have the excess removed by dropping the pan or taking the vehicle to a shop and have them suck the excess transmission fluid out of your transmission.
It's best to add just a little bit of transmission fluid at a time until it's full and check it several times while adding a little bit of transmission fluid to avoid overfilling the transmission.