The letter E in the 4l60e transmission numbers stands for “electronic” or electronic shift.
So if you have a 4l60e transmission and it has the e at the end of the numbers then it means that your 4l60e transmission has electronic shifting.
The 4l60e transmission has been in production for over twenty years and actually even longer when you take into consideration that the 4l60 transmission came from the 4l60 or 700R4 transmission.
So in short the e at the end of the 4l60e stands for electronic shifting.
It's a newer type of transmission that uses electronics for shifting the transmission.