Envoy 4WD L6-4.2L VIN S (2003)
Transfer Case Actuator: All Technical Service Bulletins
Drivetrain - Shudder/Binding/Feels Like Stuck in 4WD
File In Section: 04 - Driveline Axle
Bulletin No.: 02-04-21-008A
Date: February, 2003
TECHNICAL
Subject:
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)
Models:
2002-2003 Chevrolet TrailBlazer
2002-2003 GMC Envoy
2002-2003 Oldsmobile Bravada
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).
Condition
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.
Technician Diagnosis
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.
Correction
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:
^
Ensure that the tires are inflated to the recommended tire pressure as listed on the tire placard on the driver's door.
^
Use a tire tread depth gauge to determine the tread depth. The tire tread depth must be nearly equal on all four corners of the vehicle.
^
Ensure that the tires are all the same brand, size, and tread design.
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.
Currently, the General Motors Parts Catalog lists the following names:
^
Motor Asm, Trfer Case Encoder (This is the Encoder (Sensor). It looks like a donut with three (3) contacts on one side).
^
Gasket.
^
Actuator Asm, Trfer Case Four Whl Drv (This is the complete motor assembly consisting of the Motor and housing, the Motor Asm, the Trfer Case
Encoder (Sensor), and the gasket).
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.
