I am using this video to teach my 10 year old daughter how my car’s transmission works. It was useful for me too. When I was getting ready to do my transmission swap, understanding the inner functions of transmissions when I had never worked on one before was, well, difficult. Since the swap I have been interested in understanding the role of the shift forks and the synchros. There are many vids with animations of gear shifting, but this one is particularly good in showing schematically the role of the synchros in changing how the power travels. (BTW, the vid uses the term “dog clutch” instead of “synchro”):