Sariel gearboxes

Sariel is a Lego enthusiast that makes crazy amazing Lego models. Most are working models of real vehicles, for which he has designed multiple gearboxes to drive them with. They are all interesting and cool to watch. Here's the page for his gearbox tag. And here's a couple of them:

4 speed gearbox

A video of it:


And a 2 speed automatic gearbox. It automatically changes to a lower gear when receiving resistance.