I am not sure whether you drive a manual or an automatic, but the manual needs 5 liters when empty, the automatic 7 liters.
While the manual needs 75W90 fluid, the automatic needs fluid type T (which is different).
So it still is possible your transmission was dealing with low level fluid and still is, and also possible you used the wrong fluid. Also possible there has been dirt build up inside the transmission which came loose with the change of fluid. It is recommended to flush the transmission for that purpose. But that requires around 10 liters. A pretty expensive way but in the end a lot less expensive then replacing the entire transmission.
Also what NP says is smart to check too. If you don't know how to do that, feel free to ask.
Driving a BMW318i with LPG at the moment. Had a 2.0 RAV4.1 1997 3drs 4WD euro model w/ABS dual sunroof blue two tone previously.