DESCRIPTION
The BW 44-44 is an electronically controlled active full-time transfer case.
A wet clutch in the transfer case is used to control torque transfer to the front and rear axles. A low range gear reduction system provides increased low speed torque capability for off road operation. The low range provides a 2.64:1 reduction ratio.
OPERATION
The input gear is splined to the transmission output shaft. The input gear drives the mainshaft through the planetary assembly and range sleeve. The front output shaft is operated by a drive chain that connects the shaft to a drive sprocket on the mainshaft. Depending on traction conditions, the DTCM will modulate the electromagnetic clutch assembly to vary the amount of torque applied to the front axle. Torque is transmitted through the input shaft to the clutch and drive sprocket assembly, and is transferred directly to the rear propeller shaft, and to the output shaft and front propeller shaft by the drive chain. The oil pump circulates gear lube throughout the case to provide clutch cooling.
The shift motor consists of a permanent magnet D.C. motor with gear reduction to convert a high speed-low torque device into a low speed-high torque device. The output of the device is coupled to a shaft which internally moves the range fork that change the transfer case operating ranges. The shift motor uses a digital encoder to monitor the shift motor position. The motor is rated at 20 amps maximum at 25° C (77° F) with 14 volts at the motor leads.
The transfer case shift motor responds to the Drive Train Control Module (DTCM) commands to move the transfer case shift range fork, as required, to obtain the correct transfer case operating range indicated by the instrument panel mounted selector switch. The motor only shifts between 1:1 ranges, 2.64:1 range, and neutral. Switch changes between 2WD, 4WD Auto and 4WD Lock are handled by the transfer case coil.