Shudder, Rocking Motion, Binding, Feels Like Vehicle is Stuck in 4WD (Crow Hop) When Turning at Low Speeds (Replace Transfer Case Encoder Sensor and Reprogram TCCM)

This bulletin is being revised to update the service procedure and incorporate the fluid exchange. Please discard Corporate Bulletin Number 02-04-21-008 (Section 04 -- Driveline Axle).

Some customers may comment that when turning, the vehicle feels like it is binding, or the vehicle feels like it is stuck in 4WD (crow hop), or that the 4WD system is not working correctly. A shudder type sensation is felt.

This intermittent condition may be difficult to duplicate. The potential is there at all times for the Bravada. The potential is only present in the Auto Mode of the transfer case with the TrailBlazer or Envoy.

Important: It is extremely important to check all of the tires before repairs are attempted for these types of customer concerns. Mismatched tires may cause these type of customer concerns. Inspect the tires in the following areas:

Important: Pay particular attention so that the proper parts are replaced. The parts terminology is somewhat confusing. You will be replacing the encoder (sensor) and gasket not the complete motor assembly.

Use the following procedure to replace the Motor Asm, Trfer Case Encoder (Sensor) and Gasket.

1. If the vehicle is a TrailBlazer or Envoy, place the 4WD selector switch in the 2 HI position.
2. Raise the vehicle.
3. Disconnect the wiring harness connector at the top of the transfer case.



4. Remove the Actuator Asm, Trfer Case Four Whl Drv. (Motor) mounting bolts.
5. Remove the motor from the transfer case and set aside.



6. Position an oil drain container into position under the transfer case drain plug. Remove the drain plug and allow the transfer case to drain.
7. Position the motor on a work bench and you will see four retaining tabs that retain the gasket to the motor. Release the tabs to allow removal and discard the gasket.

Important: Gently lift and tilt the sensor toward the wiring connector wiring to disconnect it. You will notice the two wires to the motor. The red and black wires go to an internal connector within the motor housing. The black plastic connector for these wires does not have a locking tab and is easily disturbed.

8. Lift/pry the sensor from the motor shaft. Disconnect the sensor from the wiring harness.

Important: Look at the motor where you just removed the sensor. You will notice the "Hex" in the casting where the new sensor will seat when properly installed.

9. Connect the wiring harness to the sensor.
10. Gently insert a suitable tool along side the red and black wires and press down on the black plastic connector to ensure the connector is in the proper position.
11. Properly align the key way of the sensor on the shaft and install the sensor. Ensure that the hex on the sensor fits in the hex of the casting.
12. Install the new gasket assembly.



13. Inspect the positioning of the gasket and the motor shaft. If necessary to align them as shown, perform the following steps.

•	Connect a fused jumper to the transfer case encoder motor connector red wire and the other end to a positive battery terminal.

•	Connect another jumper to the transfer case encoder motor connector black wire and momentarily touch the other end of this wire to the ground terminal of a battery. This will cause the motor shaft to turn to allow alignment as shown.

Important: Inspect the encoder motor attachment face for the presence of the two (2) locating sleeves. If missing from the encoder motor, they need to be retrieved from the transfer case and reinstalled into the encoder motor before installation.

14. Position the motor to the transfer case and install the retainers.

Tighten
Tighten the bolts to 16 N·m (12 lb ft).




15. Apply pipe sealant, P/N 12346004 (Canadian P/N 10953480), or equivalent, to the drain plug threads. Install the transfer case drain plug.

Tighten
Tighten the plug to 27 N·m (20 lb ft).

16. Refill the transfer case with 1.8 L (2 qts) of Auto Trac II Transfer case lubricant, P/N 12378508 (Canadian P/N 10953626).
17. Apply pipe sealant, P/N 12346004 (Canadian P/N 10953480), or equivalent, to the fill plug threads. Install the fill plug.

Tighten
Tighten the plug to 27  N·m (20 lb ft).

18. Lower the vehicle.
19. Connect the Tech 2® and use SPS reprogramming to reprogram the transfer case control module (TCCM) with TIS software version 11, released October 2002 or newer.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: