Transfer Case - Nvg 263-NP1 (Selectable): Overview GMC Sierra 1500 HD

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step checks that the scan tool is communicating with the transfer case shift control module (TCCM).
2. 3. This step checks the presence of DTCs which begin with"U" indicating some other module is not communicating.
3. 4. This step checks to see if other modules are interfering with the TCCM operation.
4. 6. This step checks for TCCM DTCs.
5. 7. This step verifies if the TCCM has power and ground. The TCCM will not communicate without the Battery Positive Voltage circuit functioning.

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Scheme 700

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step inspects for the visual operation of the neutral indicator. Command both the ON and OFF states.
2. 3. This step tests for voltage at the neutral indicator feed side of the transfer case select switch.
3. 4. This step verifies that the transfer case shift control module is proving ground to the neutral indicator.
4. 5. This step tests if ground is constantly being applied to the neutral indicator.
5. 6. This step tests the control circuit of the neutral indicator for a short to voltage or an open.
6. 7. This step tests the control circuit of the neutral indicator for a short to ground.

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Scheme 702

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests for proper operation of the transfer case mode select switch.
2. 3. This step tests the mode switch for proper resistance values in all mode switch states.
3. 4. This step tests the switch signal wire for a short to ground, short to voltage, or high resistance

Scheme 703

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the encoder motor for an internal short to ground.
2. 3. This step helps isolate motor malfunctions from the transfer case shift control module and wiring.
3. 4. This step test for an open, high resistance, short to ground or short to voltage.

Scheme 704

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step checks for a voltage reading on the scan tool.
2. 3. This step tests the encoder circuit for a current malfunction.
3. 4. This step tests for an internal encoder malfunction which is present only in certain areas of the encoder sensor.
4. 5. This step tests for proper reference voltage at the encoder.
5. 6. This step tests the 5 volt regulator encoder circuit for a short to voltage, short to ground, an open or high resistance.
6. 7. After determining if the reference voltage measured in Step 4 is correct, Step 6 reviews the reading originally measured in Step 3 to see if it is higher or lower than what is expected. This step helps determine whether the encoder signal circuit is being pulled high or low.
7. 8. This step tests the encoder signal circuit and the encoder low reference circuit for a short to voltage.
8. 9. This step helps determine a faulty encoder.
9. 10. This step tests the encoder signal circuit and the encoder low reference circuit for an open or a short to ground.

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Scheme 706

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests for proper reference voltage to the transfer case shift control module on the 4WD LO circuit.
2. 3. This step tests the 4WD LO circuit for a short to voltage.
3. 4. This step tests the 4WD LO circuit for an open or high resistance.
4. 5. This step repairs the 4WD LO circuit for a short to voltage.

Scheme 707

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the front axle circuit for a current malfunction.
2. 3. This step helps determine if the failure is the result of a short to voltage or ground.
3. 4. This step helps determine if the front axle control circuit is shorted to ground.
4. 5. This step tests the integrity of the front axle switch and the ignition 3 voltage circuits.
5. 6. This step tests the front axle control circuit for short to ground.
6. 7. This step tests the front axle switch circuit for short to voltage.
7. 8. This step tests the front axle ignition 3 voltage circuit and the front axle switch circuit for an open or short to ground.
8. 9. This step tests the front axle control circuit and the front axle ground circuit for an open or high resistance.

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Scheme 709

The number below refers to the step number on the diagnostic table

1. 2. This step replaces the transfer case shift control module.

Scheme 710

Symptoms - Transfer Case

1. DTCs are not set.
2. The control modules can communicate via the serial data link.
3. Review the system operation in order to familiarize yourself with the system functions. Refer to «Transfer Case Description and Operation»(ref-188981-S20874597322005091300000) .
4. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
5. Inspect the automatic transfer case for the proper fluid level.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the electrical function of the front axle actuator and helps determine mechanical and electrical malfunctions.
2. 3. This step tests for proper power and ground at the front axle actuator.
3. 4. This step tests the operation of the front axle control circuit.
4. 5. This step helps determine if the transfer case shift control module is able to monitor the front axle switch.
5. 6. This step tests the front axle switch circuit for an open or high resistance.
6. 7. This step measures the voltage between the front axle feed circuit and ground.
7. 8. This step tests the front axle control circuit for an open or high resistance.
8. 9. This step inspects the front axle for a mechanical malfunction.
9. 10. This step tests for open fuse in the front axle feed circuit.

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The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the electrical function of the front axle actuator and helps determine mechanical and electrical malfunctions.
2. 3. This step tests for proper voltage and ground at the front axle actuator.
3. 4. This step tests the operation of the front axle actuator control circuit.
4. 5. This step tests the electrical function of the front axle actuator control circuit.
5. 6. This step tests for proper supply voltage to the front axle actuator.
6. 7. This step tests for open fuse in the ignition 3 voltage circuit.
7. 8. This step tests the front axle actuator control circuit for an open or high resistance.
8. 9. This step tests the front axle actuator signal circuit for an open or high resistance.
9. 10. This step helps determine if the front axle actuator has a mechanical malfunction.
10. 11. This step tests the front axle switch circuit for a short to voltage.
11. 12. This step inspects the front axle for a mechanical malfunction.

Scheme 713

Scheme 714

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the functionality of the mode switch.
2. 3. This step tests the modules ability to operate the transfer case modes.

Scheme 715

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step helps determine whether the front axle switch is functioning properly.
2. 3. This step helps determine whether the front axle switch is locking and unlocking.
3. 4. This step tests transfer case clutch performance.

Scheme 716

The number below refers to the step number on the diagnostic table.

1. 2. This step determines whether the failure is the result of a malfunctioning transfer case shift control module or the IPC.

Scheme 717

The number below refers to the step number on the diagnostic table.

1. 2. This step determines whether the failure is the result of a faulty transfer case shift control module or the IPC.

Scheme 718

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the transfer case electrical control of the lamp circuits.
2. 3. This step helps determine if there is a short to ground in the suspect lamp circuits.
3. 4. This step tests the suspect lamp circuits for a short to ground.
4. 5. This step repairs a short to ground in the suspect lamp circuit.

Scheme 719

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step helps to determine if the transfer case shift control module has the ability to command the encoder motor.
2. 3. This step determines if motor control A and motor control B circuits being shorted together is causing a shift block.
3. 4. This step determines if the motor control A and motor control B circuits are shorted together within the module.
4. 5. This step determines if a binding shift lever detent shaft is causing a shift block.
5. 6. This step has the transfer case removed and repaired.
6. 7. This step determines if the PNP switch is sending the correct range signal.
7. 8. This step replaces the transfer case shift control module.

Scheme 720

Scheme 721

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step determines the position of the front axle switch.
2. 3. This step helps determine if the front axle will not engage.
3. 4. This step helps determine if the front axle will not disengage.

Scheme 722

The numbers below refer to the step numbers on the diagnostic table.

1. 2. This step tests the transfer case electrical control of the lamp circuits.
2. 3. This step helps determine module failures.
3. 4. This step tests the affected lamp circuit for an open or high resistance.
4. 5. This step tests the lamp feed circuit for an open or short to ground.

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1. Raise and suitably support the vehicle. Refer to «JACKING AND LIFTING»(ref-188958) .
2. Remove the transfer case shield bolts, if equipped.
3. Remove the transfer case shield, if equipped.

Scheme 737

1. Position the transfer case shield to the crossmember, if equipped. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) .
2. Install the transfer case shield bolts, if equipped. Tighten Tighten the bolts to 20 N.m (15 lb ft).
3. Lower the vehicle.

Transfer Case Description and Operation

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 Will Not Shift-Electrical condition.

The NVG 263 transfer case provides the driver with 4 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
4. 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

1. The ignition switch is in RUN.
2. The automatic transmission is in Park or Neutral-clutch depressed on manual transmissions.
3. 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 transfer case mainshaft and the transmission output shaft. Neutral position may be obtained only if the following criteria has been met

1. The ignition switch is in RUN.
2. The automatic transmission is in Park or Neutral-clutch depressed on manual transmissions.
3. The vehicle speed is below 5 km/h (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 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.

Scheme 738

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 NVG has some changes from prior model years. The NVG 263 has a new style encoder motor. The oil pump on the HD variations is now the same as the SHD variation. Along with the oil pump change, the oil pump suction pipe and screen were changed to the SHD style. The NVG 263 HD now uses a different rear output shaft.

Scheme 739

The transfer case is shifted by an encoder motor (9) on the shift detent lever shaft. The shift detent lever shaft rotates the cam shaped shift detent lever (10) and moves the high/low range shift fork (11) or the 2/4 wheel drive mode shift fork (8). Depending on the selected mode or range, the shift forks move either the high/low range sleeve (4) for the high/low range planetary assembly (3) or the synchronizer sleeve (6) for the 2/4 wheel drive mode.

In 2WD mode, the engine power from the transmission (1) is delivered to the input shaft (2). The engagement teeth on the inside of the input shaft (2) are engaged to the outer teeth on the high/low range sleeve (4). The high/low range sleeve (4) is slip splined to rear output shaft (5). The engine power flows from the high/low range sleeve (4) to the rear output shaft (5) and delivered to rear propeller shaft (7).

Scheme 740

In 4HI mode, the engine power from the transmission (1) is delivered to the input shaft (2). The engagement teeth on the inside of the input shaft (2) are engaged to the outer teeth on the high/low range sleeve (3). The high/low range sleeve (3) is slip splined to the rear output shaft (4). During a shift mode from 2HI to 4HI, the cam profile on the shift detent lever (14) pushes the 2/4 wheel drive mode shift fork (9) and the synchronizer sleeve. The sleeve, engaging the synchronizer (5), equalizes the front propeller shaft (12) and rear propeller shaft (7) speeds. The sleeve then engages to the 2/4 wheel drive synchronizer gear (8), which is splined to the drive sprocket (6). The engine power flow for driving the front propeller shaft (12), now travels from the rear output shaft (4) to the synchronizer hub, which is splined to the rear output shaft (4). The power flows from the synchronizer hub to the sleeve and then to 2/4 wheel drive synchronizer gear (8).

The power flow is transmitted by a chain (10) to the driven sprocket on the front output shaft (11) and to the front propeller shaft (12). The front and rear propeller shafts are being driven at equal RPM, therefore giving a four wheel drive mode. This mode should only be used for extra traction. Using this mode on dry pavement causes tire scuffing when turning.

Scheme 741

During a range shift request to 4LO, a separate cam profile, on the same shift detent lever (12), moves the high/low shift fork (13). The high/low shift fork (13) moves the high/low range sleeve (6) rearward. The high/low range sleeve (6) outer teeth disengage from the input shaft (2) high-speed teeth. The high/low range sleeve (6) outer teeth then engage in the high/low planetary carrier teeth (5). The power flow is now from the transmission (1) to the planetary teeth on the input shaft (2) to the planetary gears (3) in the carrier. Rotating the planetary gears (3), which are engaged in the annulus gear (4), rotates the planetary carrier. The planetary carrier delivers the power to the high/low range sleeve (6). The high/low range sleeve (6) then drives the rear output shaft (7), providing a 2.72:1 gear ratio reduction to the rear output shaft (7). The 2/4 wheel drive synchronizer (8) is still engaged to drive the drive sprocket (9), as in the 4HI position, providing the engine power to the rear propeller shaft (10) and to the front propeller shaft (11).