Transmission especially the automatics can overheat. The causes range from bad clutch, wrong fluid, overfilled or underfilled transmission and bad oil cooler.
Modern transmissions are not as simple as they used to be. We can say that transmissions have become smart with the introduction of AI machine learning algorithms.
Current measurement is best done by clamping the conductor carrying current instead of an ameter in series. This method is good for measuring parasitic drain.
Replacing old transmission fluid with fresh one at the right time is very crucial to the performance and lifespan of a transmission. Their are ways to check whether transmission fluid has worn and due for change.