Transfer Case Description and Operation: Notes

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

The Borg Warner (BW) model 4484 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.

The BW 4484 case halves are high-pressure die-cast magnesium. Ball bearings support the input shaft, 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 manual transmission fluid GM P/N 88861800 (Canadian P/N 88861801), which is red in color. An oil pump pumps the fluid through the mainshaft oil gallery to the gears and bearings.