WARNING: modification replace default items
Engines
This mod change Scania V8 engines: Scania DC16.121 (590hp), Scania DC16.122 (660hp) and Scania DC16.123 (770hp):

Idle speed set to 550 RPMRev limits set to 2000 RPM (working) and 1500 RPM (neutral) to match the V8 redlineAdjusted automatic gear shift points to use the engine’s massive low-end torqueSmooth and realistic engagement of the 13th gear (Overdrive) at highway speeds (85+ km/h)Realistic high RPM behavior during engine braking to maximize cooling
Gearbox
This mod changes the retarder steps for Scania Opticruise G-series gearboxes to match real-life Scania Brake Management logic:

Step 1: 20% retarder power + 33% engine brake powerStep 2: 40% retarder power + 66% engine brake powerStep 3: 60% retarder power + 100% engine brake power + DownshiftStep 4: 80% retarder power + 100% engine brake power + DownshiftStep 5: 100% retarder power + 100% engine brake power + Downshift
Scania truck by SWISSCAT on World of Trucks

Credits:
BoL4oNoK