18 speed manual transmissions ARE possible in ETS2. You don't have to drive a Kenworth like it's a city bus (automatic)
I really enjoy "rowing my own gears" in ETS2, and it frustrates me to hear and read of people who drive with automatic gears because they say it's "impossible" to have an 18 speed transmission in ETS2. If you like, automatic gears fine, but it's not impossible to have the "real thing".
First, go on YouTube and watch all the videos by users "broburga" and "Giorgio DaTrucker" regarding Euro Truck Simulator 2 + 18 speed gearboxes. Next follow any file links they provide to get pertinent files. If their links has expired, go to ets2.lt, and search "18 speed transmission".
I won't go into details here, as these guys cover it all in great detail, and it's not that difficult.
And for those of you who don't have a gearshift controller of any kind, look up on YouTube and elsewhere "joystick as gear shift". In fact, "Giorgio DaTrucker" covers this as well.
It really pains me to hear silliness on some of the ETS2 streaming channels like "I need a 7 position gearshift, or ETS2 needs to provide me with more ranges (5!?!) to do 18 speed shifting. No and no.
I drive 18 speed Petes and Kenworths every day in ETS2, and you can too.