Chrysler Corporation

Fca US LLC

Frank C Thompson, Iv

Michael W Gapski

Mark Thompson

A method of controlling a four wheel drive (4WD) low range shift in a vehicle is provided. The vehicle has a powertrain including a transmission that drives a transmission output shaft to provide drive torque to a driveline including a power transfer unit (PTU) that delivers torque to front drive wheels and a rear differential unit (RDU) that delivers torque to rear drive wheels. The PTU and RDU are selectively rotatably coupled to each other through a propeller (prop) shaft. The PTU and the RDU are commanded into a neutral position. A clutch at the RDU is commanded to selectively engage to a degree that communicates a desired amount of torque from the prop shaft to the RDU. A determination is made that an output speed of the transmission output shaft is synchronized to match a speed of the RDU and the RDU is commanded to shift into 4WD low.

Method for synchronized four wheel drive low range shifts with vehicle in motion

An on-demand four wheel drive system for a vehicle having a front drive train, a rear drive train, and a transfer case. The system includes a sensor system operable to detect the speed of the front drive train and the speed of the rear drive train. The system also includes a controller operable to cause the transfer case to supply input torque to the front drive train and the rear drive train when the sensor system detects that the speed of the rear drive train exceeds the speed of the front drive train by a predetermined amount. The controller is further operable to cause the transfer case to limit the amount of input torque supplied to the front drive train when the sensor system detects that the speed of the front drive train exceeds the speed of the rear drive train.

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Livonia, MI, United States of America

Frank C Thompson, Iv