The FKM Garage system is famous in the ETS2 community for its technical depth:

This version was a ground-up reconstruction of the audio samples to improve clarity and compatibility with major truck mods like Fred's Scania and the RJL Scania series. Signature Features

Includes gearbox whine, retarder sounds, and opticruise shifting audio. It also features directional sound , meaning the exhaust sounds different depending on which side of the truck you are standing. Where to Find It

The mod's journey began as a project to bring "brutal" and realistic engine audio to Scania trucks, focusing on the distinct roar of V8 and L6 (Inline 6) engines.