This is a ZF Ecomat automatic gearbox. It was (it’s been replaced by a newer model) one of the two automatic transmissions that equip most city buses (the other is by Voith and worth a post in itself). There’s nothing unusual about it and it’s just like the one you’d have in your car, if you’re an American, or probably wouldn’t, if you’re one of the rest of us, but much bigger.
This is a Class 172 train. It’s used on several commuter routes in Britain and is one of those trains which have an engine under each carriage. There’s nothing unusual about it. This particular one runs in London, but not for much longer as the route has become so crowded it’s going to be electrified and equipped with bigger and electric rolling stock.
What’s unusual is that the two are combined. The Class 172 has two or three Ecomats sitting under it. This gives to the unusual experience of a train that sounds and feels like a bus as it works its way up and down the box with noticeable gearchange noises.
You want to know what it sounds like? Somebody has thought about you and made a video.
What’s strange is not just that a video has been made of a suburban train journey but there are several others, some of which have had thousands of views.