Abstract: A four wheel drive assembly 10 including a torque transfer assembly 60 which operates under the control of the controller 62 and which receives and selectively transfers a certain desired amount of torque to a front axles 14, 15 and to the rear axles 14 17. The amount of transferred torque varies depending upon the occurrence of a sensed slip condition the use of a pre-emptive slip control mode of operation in which the controller 62 determines that it is likely that a slip may occur. Particularly, controller 62 is allowed to enter the preemptive mode of operation only after an actual slip has occurred and the controller 62 exits this preemptive mode of operation upon the occurrence of a certain event or condition or upon the passage of a certain amount of time.

Abstract: A method and apparatus for overcoming negative torque transfer in a passive coupling (43) in a vehicle (10) having all wheel drive. The vehicle (10) includes a front driveshaft (22), a rear driveshaft (26), with the passive coupling (43) connecting the front driveshaft (22) and the rear driveshaft (26). The vehicle (10) also includes a transmission (30) operatively connected to the passive coupling (43). The method includes determining negative torque transfer in the passive coupling (43) and requesting the vehicle (10) to increase transmission output equal to the negative torque transfer.

Abstract: A method and apparatus for overcoming negative torque transfer in a passive coupling (43) in a vehicle (10) having all wheel drive. The vehicle (10) includes a front driveshaft (22), a rear driveshaft (26), with the passive coupling (43) connecting the front driveshaft (22) and the rear driveshaft (26). The vehicle (10) also includes a transmission (30) operatively connected to the passive coupling (43). The method includes determining negative torque transfer in the passive coupling (43) and requesting the vehicle (10) to increase transmission output equal to the negative torque transfer.

Abstract: A four wheel drive assembly 10 including a torque transfer assembly 60 which operates under the control of the controller 62 and which receives and selectively transfers a certain desired amount of torque to a front axles 14, 15 and to the rear axles 14 17. The amount of transferred torque varies depending upon the occurrence of a sensed slip condition the use of a pre-emptive slip control mode of operation in which the controller 62 determines that it is likely that a slip may occur. Particularly, controller 62 is allowed to enter the preemptive mode of operation only after an actual slip has occurred and the controller 62 exits this preemptive mode of operation upon the occurrence of a certain event or condition or upon the passage of a certain amount of time.

Abstract: A method and system 10 for controlling a transfer case 32 of a four-wheel drive vehicle 12. The vehicle 12 includes a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 47, to a driver-operated control 48, and to a transfer case clutch 38. Controller 40 operates transfer case 32 in several modes including an automatic four-wheel drive mode and a “locked” four-wheel drive high mode. Controller 40 estimates the amount of heat generated by clutch 38 by monitoring the difference in the speed between driveshafts 22 and 26 and by monitoring the position of the vehicle's throttle. Controller 40 automatically shifts from the automatic four-wheel drive mode to the locked four-wheel drive high mode when the estimated amount of heat exceeds a certain threshold level.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to transfer case 32. Controller 40 selectively transmits a torque control or minimum duty cycle signal to transfer case 32, which is at least partially based upon the angular position of the vehicle's steering wheel and the speed of driveshafts 22, 26.