Download More Transmissions v1.4 1.16.X mod for Euro Truck Simulator 2, tested on 1.16 version.
This Mod includes 7 transmissions for every truck. Although the video shows barely any difference for the acceleration, they do increase the maximum rpm to km/h, meaning if you are using a better engine, there will be more of a difference if using another transmission type.
More updates coming soon! (Sorry about old format)