Some modern transmissions do not require oil maintenance because they are filled with lifetime fluid that supposedly last the lifetime of the transmission.
The eCVT in hybrid cars have electric motor/generator sets in it which the engine and regenerative brake system uses to charge the hybrid battery. A wrong transmission fluid in it will cause short circuit, malfunction and damage.
Transmission fluids expand as they heat up. This changes the volume and consequently the fill level. This makes the temperature st which fluid level is checked important.
Coolant can gain access to transmission through the transmission oil cooler. The oil cooler can leak internally causing the coolant and oil chambers to be linked.
If a transmission was previously not properly maintained by not carrying out regular oil change, changing the oil later might cause it to slip or not shift at all.
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.
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.
