[robocat]

Look at a workshop maintenance manual to get a rough idea. One car I had, about a third of the book was dedicated to the automatic transmission. Auto transmissions are very complex.

[mulmen]

Yes, in a past life I rebuilt automatic transmissions so I am familiar with their complexity.

Transmissions are complex but so are a lot of things. Internal combustion engines are more complex than transmissions.

Pages in a shop manual are a proxy for the complexity of service, not of the component itself.