Transfer Case Shift Control Switch

Fig 1: Transfer Case Shift Control Switch

Courtesy of GENERAL MOTORS CORP.

The NVG 263 transfer case features a three button shift control switch located on the instrument panel. When the ignition is in the RUN position, the transfer case shift control module (TCCM) 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 TCCM has received the request for a new mode/gear position. The lamp continues to flash until all shifting criteria has been met and the new mode/gear position has been engaged. Once the new mode/gear position is fully active, the switch indicator for the new position remains ON constantly. In the event that the TCCM can not or will not complete the shift, the indicator returns to the previously selected position; this is a Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode condition.

The NVG 263 transfer case provides the driver with 4 manual mode/gear positions:

• 2HI - 2 Wheel Drive high range
• 4HI - 4 Wheel Drive high range
• 4LO - 4 Wheel Drive low range
• Neutral

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

• The ignition switch is in RUN.
• The automatic transmission is in Park or Neutral - clutch depressed on manual transmissions.
• 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 rear axle rotating the transmission output shaft. Neutral position may be obtained only if the following criteria has been met:

• The ignition switch is in RUN.
• The automatic transmission is in Park or Neutral - clutch depressed on manual transmissions.
• The vehicle speed is below 5 km/h (3 mph).
• The transfer case is in 2HI mode.

Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10 seconds. When the system completes the shift to neutral, the red neutral lamp illuminates.

A shift to the neutral position allows the vehicle to be towed without rotating the transmission output shaft. In the neutral position, the rear propeller shaft rotates the transfer case rear output shaft, in turn rotating the oil pump, thus providing constant lubrication during towing. This neutral position is a 4WD neutral, meaning the front and rear outputs of the transfer case are engaged as though in 4HI. With a disconnecting front axle, there is no power flow to the front wheels, thus allowing towing with the front wheels off the ground or flat towing without driveline binding.

The NVG 263 transfer case is available in 2 variations, depending on the engine and transmission configurations. The variations allow the transfer case to handle different torque loads. When servicing the transfer case, it is important to understand which variation is being serviced because of the difference in parts.

The HD and the SHD model share many of the same components, but the increased torque capacity of the SHD requires a double row input bearing, larger diameter rear output shaft, rear output shaft bearing higher capacity, larger rear seal and case halves machined differently.

The following changes were made to the NVG 263 for this model year:

• The case half bolts now use a cup style aluminum washer, which allow using the bolts again.
• The rear output shaft is machined differently at the retaining ring groove for the synchronizer retaining ring and the retaining ring is now a smaller diameter.
• There is not a roller on the pin of the range shift fork.