US Patent 11041534 Method of controlling transmission in neutral

Ideally, when a transmission is in Neutral, no torque should be exerted on the vehicle wheels by the powertrain. However, even with all clutches in a gearbox disengaged, some torque may be transmitted from a turbine shaft to the transmission output due to clutch drag and transmission component inertia. To avoid transmitting torque, a subset of clutches may be engaged to produce an input tie-up state, this holding the turbine shaft against rotation while permitting rotation of the output element.