US Patent 10144284 Four-wheel drive vehicle control system and methods

Methods and systems are provided for operating a four-wheel drive powertrain of a vehicle. In one example, a method may comprise: in response to a desired shift from a four-wheel drive mode to a two wheel-drive mode: decreasing a transfer case torque output to a secondary driveline to a lower first level and disengaging a disconnect device of the secondary driveline; increasing the transfer case torque output from the lower first level to a higher second level over a duration; and after the duration, reducing the transfer case torque.