Caused by downsizing of combustion engines, the torque fluctuation at the crankshaft induces torsional vibrations in the powertrain. Manual transmissions and dual clutch transmissions are particularly sensitive to gear-rattle noise. Gear-rattle noise arises from oscillations of loose parts with clearance, e.g. idler gears, synchronizer rings and gearshift sleeves. The aim of this research is the formulation of a gear oil for the application in a manual transmission to minimize gear rattling noise. Acoustic measurements on a gear-rattle noise test bench verify the noise reduction of the...