Transfer Case Description and Operation: Notes

The Borg Warner (BW) model 4493/4494 NR4 transfer case is a 2-speed, full-time 4WD, transfer case. The transfer case has an external planetary type differential, which has 2 different sets of pinion gears. The planetary differential provides a 40/60 torque split front/rear full-time. This means the front and rear propeller shafts are constantly being driven for maximum traction in all conditions. A high/low planetary carrier assembly provides the high and low ranges, which is a 6-pinion gear, sun gear, and annulus gear arrangement, giving a 2.64 low range reduction ratio in the BW 4493 and a 4:1 ratio in the BW 4494.

The BW 4493/4494 case halves are high-pressure die-cast magnesium. Ball bearings support the input shaft, the mainshaft, the front output shaft, and the rear output shaft. A needle roller bearing is located inside of the input shaft gear to support the front of the mainshaft. The rear of the mainshaft is supported by a bronze bearing inside the rear output shaft. The transfer case requires DEXRON®VI Automatic Transmission Fluid (ATF) GM P/N 88861003 (Canadian P/N 88861004), which is red in color. An oil pump pumps the fluid through the mainshaft oil gallery to the gears and bearings.