Hummer H2. Manual - part 2702

Fig. 155: Transfer Case Shift Control Switch 
Courtesy of GENERAL MOTORS CORP. 

The BW 4484 transfer case features a 4-button shift control switch located on the instrument panel. When the 
vehicle has the ignition key in the RUN position, the transfer case shift control module starts monitoring the 
transfer case shift control switch to determine if the driver desires a new mode/gear position. At a single press 
of the transfer case shift control switch, the lamp of the new desired position begins flashing to inform the 
driver that the transfer case shift control module has received the request for a new mode/gear position. The 
lamp continues to flash until all shifting criteria have been met and the new mode/gear position has been 
reached, or has been engaged. Once the new mode/gear position is fully active, the switch indicator lamp for the 
new position remains ON constantly. 

During normal driving situations, the transfer case operates in the 4HI mode. When the 4HI mode is selected, 

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

the transfer case shift control module sends 12 volts to an electrical motor, which is the transfer case encoder 
motor. This motor rotates the transfer case shift detent lever shaft which moves the shift forks and range sleeve 
to obtain different modes/ranges. 

The BW 4484 transfer case has the added feature of also providing the driver with 3 manual mode/range 
positions: 

z

4HI - 4 Wheel Drive High Open  

z

4HI Lock - 4 Wheel Drive High Locked  

z

4LO Lock - 4 Wheel Drive Low Locked  

The driver may choose to select any of these mode/range positions while driving the vehicle. However, the 
transfer case will not allow a shift into or out of 4LO Lock unless the following criteria has been met: 

z

The engine is running.  

z

The automatic transmission is in Neutral.  

z

The vehicle speed is below 5 km/h (3 mph).  

This transfer case also has a Neutral position. A shift to the Neutral position allows the vehicle to be towed 
without the transmission output shaft rotating. Refer to the Owners Manual for instructions for proper towing of 
the vehicle. 

Neutral position may be obtained only if the following criteria have been met: 

z

The engine is running or the ignition is ON.  

z

The automatic transmission is in Neutral.  

z

The vehicle speed is below 5 km/h (3 mph).  

z

The transfer case is in the 4HI mode.  

Once these conditions have been met, press and hold both the 4HI and 4LO Lock buttons for 10 seconds. When 
the system completes the shift to Neutral, the red Neutral indicator illuminates. 

The BW 4484 transfer case has one other additional feature along with the 3 modes. The Electronic Rear 
Differential Lock can only be used in the 4LO Lock mode with a vehicle speed at or below 32 km/h (20 mph). 

4HI Mode Power Flow 

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

Fig. 156: 4HI Mode Power Flow 
Courtesy of GENERAL MOTORS CORP. 

When the BW 4484 is in 4HI mode, the engine power flows from the transmission to the input shaft (1). The 
input shaft (1) is connected to the mainshaft (3) by the high/low range sleeve (2). The high/low range sleeve (2) 
outer teeth are engaged with the input shaft (1) high-speed teeth. The range collar is slip splined to the 
mainshaft (3). The mainshaft (3) delivers the power flow to the planetary differential (6), which splits the torque 
40 percent through the front differential pinion gears (5) to the front sun gear (10). The torque to the front axle 
then goes through the drive sprocket (4), via the chain (11) to the front output shaft (12) and to the front axle. 
The differential planetary splits the torque 60 percent to differential rear pinion gears (9) and rear sun gear (7). 
The rear sun gear is connected to the rear output shaft (8) and the torque flows to the rear axle. In the 4HI mode, 
if traction is lost to one axle and the tires spin, the Traction Assist System (TAS) applies braking to the spinning 
tires and the engine power is delivered to the other tires. 

4HI Lock Mode Power Flow 

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2

  

Fig. 157: 4HI Lock Mode Power Flow 
Courtesy of GENERAL MOTORS CORP. 

When shifting to the 4HI Lock mode, the encoder motor (4) turns the shift detent lever shaft (5), to rotate the 
shift detent lever cam (8). The cam action of the shift detent lever cam (8) moves the lockup mode shift fork 
rearward along with the lockup shift assembly sleeve (2). The lockup shift assembly sleeve (2) locks the 
mainshaft (1) to the drive sprocket (3). Torque is sent by the chain (6) to the front output shaft (7) and to the 
front axle. The torque distribution in this mode is now determined by vehicle dynamic conditions and weight 
distribution. The planetary differential is not operating, and both the front and rear propeller shafts are being 
driven at equal RPMs, therefore giving a 4 high lock mode. This mode should only be used for extra traction 
during off road use. Using this mode on dry pavement causes tire scuffing. 

4LO Lock Mode Power Flow 

 

2004 Hummer H2 

2004 DRIVELINE/AXLE Transfer Case - BW 4484 - Hummer H2