Transfer Case - Nvg 263-NP1 (Selectable): Other GMC Sierra 2500

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS .

Tools Required

1. J 8092 Universal Handle
2. J 43484 Front Output Shaft Seal Installer

Scheme 271

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1. Raise the vehicle.
2. Remove the transfer case shield from the crossmember (if equipped). Refer to «Transfer Case Shield Replacement»(ref-175704-S30724250892005042700000) .
3. Remove the front propeller shaft from the vehicle. Refer to «PROPELLER SHAFT REPLACEMENT - FRONT»(ref-175687-S01230655242005042600000) .
4. Insert a flat-tipped screw driver in the inner race.
5. Pry the inner race back.
6. Insert a small pry bar in the inner race. Important: When performing the following service procedure, the outer part of the seal will slightly move out of the transfer case with the inner part seal.
7. Pry the inner part of the seal from the outer seal body.
8. Remove the inner part of the seal.
9. Insert a flat-tipped screw driver or small pry bar in the space between the outer race of the seal and the transfer case.
10. Pry the outer race out of the transfer case.
11. Remove the outer part of the seal.

1. J 37668-A Output Shaft Seal Installer
2. J 45380 Transfer Case Rear Bushing Remover and Installer

Scheme 276

1. Raise and suitably support the vehicle.
2. Remove the transfer case shield. Refer to «Transfer Case Shield Replacement»(ref-175704-S30724250892005042700000) .
3. Remove the rear propeller shaft. For vehicles equipped with the one piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - ONE PIECE»(ref-175687-S13666381282005042600000) . For vehicles equipped with the two piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - TWO PIECE»(ref-175687-S33480821712005042600000) .
4. Remove the transfer case rear output shaft seal.
5. Inspect the rear output shaft bushing for scoring or wear.
6. Remove the rear output shaft bushing if required, using the J 45380 . Install the finger section of the J 45380 in front of the bushing. Install the tube and forcing screw to the finger section. Ensure the forcing screw is backed out. Using a wrench on the forcing screw, remove the rear output shaft bushing.

Scheme 277

1. Using the J 45380, install a NEW rear output shaft bushing. Install the bushing or the finger section of the J 45380. Install the finger section to the main body of the J 45380. Position the bushing and tool to the case. Using a hammer and J 45380, install the bushing.
2. Position the rear output shaft seal in the transfer case.
3. Using the J 37668-A , install the transfer case rear output shaft seal.
4. Install the rear propeller shaft. For vehicles equipped with the one piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - ONE PIECE»(ref-175687-S13666381282005042600000) . For vehicles equipped with the two piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - TWO PIECE»(ref-175687-S33480821712005042600000) .
5. Check the transfer case fluid level. Refer to «Transfer Case Fluid Replacement»(ref-175704-S06464541342005042700000) .
6. Install the transfer case shield.
7. Lower the vehicle.

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1. Raise the vehicle.
2. Remove the transfer case shield. Refer to «Transfer Case Shield Replacement»(ref-175704-S30724250892005042700000) .
3. Drain the transfer case of fluid. Refer to «Transfer Case Fluid Replacement»(ref-175704-S06464541342005042700000) .
4. Remove the front propeller shaft. Refer to «PROPELLER SHAFT REPLACEMENT - FRONT»(ref-175687-S01230655242005042600000) .
5. Remove the rear propeller shaft. For vehicles equipped with the one piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - ONE PIECE»(ref-175687-S13666381282005042600000) . For vehicles equipped with the two piece propeller shaft, refer to «PROPELLER SHAFT REPLACEMENT - TWO PIECE»(ref-175687-S33480821712005042600000) .
6. Remove the transmission shift control cable from the transfer case.
7. Remove the transfer case speed sensor electrical connector.
8. Remove the motor/encoder electrical connector.
9. Remove the transfer case vent hose.
10. Support the transmission with a suitable transmission jack stand.
11. Remove the transmission mount retaining nuts.
12. Raise the transmission high enough in order to remove the transmission mount.
13. Remove the transmission support mounting bolts.
14. Remove the transmission support from the frame.
15. Support the transfer case with a suitable jack stand.
16. Remove the transmission mount bolts.
17. Remove the transmission mount from the adapter.
18. Remove the retaining nuts for the transfer case adapter. Important: The following service procedure must be performed with the assistance from another technician.
19. Slide the transfer case straight back toward the rear of the vehicle.
20. Rotate the transfer case so that the front output shaft is above the torsion bar bracket.
21. Rotate the transfer case (with the input shaft slightly lowered) so that the transfer case is parallel to the torsion bar bracket.
22. Lower the transfer case.

J 42738 Seal Installer

Scheme 281

1. Raise the vehicle.
2. Remove the transfer case assembly. Refer to «Transfer Case Adapter Replacement»(ref-175704-S14735779032005042700000) .
3. Remove the transfer case input shaft seal.

New Venture Gear 263 Selectable Two-Speed Transfer Case

The NVG 263 transfer case features a three 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 will begin flashing to inform the driver that the transfer case shift control module has received the request for a new mode/gear position. The lamp will continue to flash until all shifting criteria has 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 will remain ON constantly.

The NVG 263 transfer case provides the driver with 3 manual mode/gear positions

1. 2HI - 2 Wheel Drive high range
2. 4HI - 4 Wheel Drive high range
3. 4LO - 4 Wheel Drive low range

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

1. The engine is running.
2. The automatic transmission is in Neutral (clutch depressed on manual transmissions).
3. The vehicle speed is below 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 transfer case main shaft and the transmission output shaft.

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

1. The engine is running.
2. The automatic transmission is in Neutral (clutch depressed on manual transmissions).
3. The vehicle speed is below 3 MPH.
4. 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 will illuminate.

View the list of major components that make up the automatic transfer case (ATC) system below.

Front Axle Actuator

The front axle actuator engages and disengages the front axle. The front axle actuator consists of a Permanent Magnetic (PM) motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit. Whenever a shift to 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the axle actuator control circuit through a current limiting driver. The front axle actuator also sends a signal to the PCM indicating when the 4WD is engaged.

Transfer Case Shift Control Module

The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information. This information is provided to the transfer case shift control module via Class 2 data bus from the powertrain control module (PCM).

Transfer Case Encoder Motor

The transfer case encoder motor consists of a permanent magnet (PM) DC motor and gear reduction assembly. It is located on the left hand side (drivers side) of the transfer case. When activated it turns the sector shaft of the transfer case (clockwise or counter clockwise) to shift the transfer case. The encoder motor is controlled with a pulse width modulated (PWM) circuit within the transfer case shift control module. This circuit consists of a driver on both the Motor Control A and Motor Control B circuits. The encoder motor is bi-directional to allow the motor to shift the transfer case from 2HI or 4HI to NEUTRAL and 4LO positions.

The transfer case encoder motor can be turned ON and OFF using a scan tool. You may also monitor Motor Control A and B circuits using a scan tool.

Transfer Case Encoder

The encoder is mounted to the transfer case encoder motor assembly and is replaced only as an assembly. The encoder converts the sector shaft position (representing a mode or range) into electrical signal inputs to the transfer case shift control module. The module detects what position the transfer case is in by monitoring the 4 encoder channels (P, A, B, and C). These inputs translate into 2HI, 4HI, NEUTRAL, and 4LO or whether the motor is still in transition between gears.

The transfer case encoder channel circuit may be monitored using a scan tool.

Vehicle Speed Sensor

There is a vehicle speed sensor mounted to the transfer case on the rear output shaft. The speed sensor is a permanent magnet (PM) generator. The PM generator produces a AC voltage. The AC voltage level and number of pulses increases as speed increases. The VSS is an input to the powertrain control module (PCM). The PCM sends this information to the transfer case shift control module via the Class 2 serial data bus.

SERVICE Indicator (4WD) Lamp

The SERVICE indicator (4WD) lamp is an integral part of the cluster and cannot be serviced separately. This lamp is used to inform the driver of the vehicle of malfunctions within the automatic transfer case (ATC) system. The SERVICE indicator (4WD) lamp is controlled by the transfer case shift control module via a Class 2 message or by a Service Indicator Control circuit.

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