Transfer Case Shift Motor
The externally mounted transfer case shift motor, located at the rear of the transfer case, turns the shift cam assembly. As the shift cam assembly turns, it positions the reduction shift fork for desired transfer case operation. An integral position sensor in the shift motor provides shift motor position information to the 4WD control module.
4WD Control Module
The 4WD control module, integral to the PCM, controls the operation of the transfer case in response to the inputs from the shift motor, MSS, BOO switch, digital TR sensor, throttle position output from the PCM, stability assist module (if equipped) and the VSS
The Borg-Warner 44-11 transfer case is available in the Explorer (A4WD) vehicle. The transfer case transfers power from the transmission to the rear axle, and also the front axle when electronically activated.
In 4x4 Auto mode, torque from the transmission is transferred to the input shaft. The input shaft output drives the rear output shaft which, in turn, drives the rear axle assembly. The electromechanical ball ramp clutch assembly drives the drive sprocket after the 4WD control module activates the clutch coil. The drive sprocket turns the drive chain and rotates the front output shaft and the front driveshaft. In the 4x4 High mode, the operation is the same as in the 4x4 Auto mode, except that the 4WD control module consistently activates the electromechanical ball ramp clutch assembly.
The high-low shift occurs when the reduction shift fork moves the high-low collar to lock the planetary gear set to the output shaft. The torque transmitted through the sun gear from the input shaft turns the front planetary gear set assembly. The front planetary gear set assembly, which is now engaged, provides transfer case speed reduction.
Saturday, May 30th, 2009 AT 5:13 AM