Forward and aft torque distribution control system and method for 4wd vehicle

A forward and aft torque distribution system and a method of controlling forward and aft torque distribution for a four-wheel vehicle having an electronically controlled clutch to control split of drive torque to be transferred to front and rear wheels are disclosed. A 4WD controller is responsive to mode selection signals from a mode changeover switch and a vehicle speed signal delivered from a vehicle speed sensor, and has control modes involving at least a LOCK mode and an AUTO mode. When the vehicle speed becomes less than a vehicle's halt discriminative vehicle speed indicative of a vehicle's halt state during the LOCK mode, the controller allows the electronically controlled clutch to be released.