Drivetrain - Transfer Case Operating Characteristics
INFORMATIONBulletin No.: 04-04-21-002D
Date: May 02, 2011
Subject: Information on Noise and Bump/Clunk Felt when Transfer Case Shifted into Four Hi (4HI), Four Low (4LO) Out of Neutral - Normal Four Wheel Drive Shifting Characteristic
Models:
2004-2012 Chevrolet Colorado
2004-2012 GMC Canyon
with Electric Shift Selectable Transfer Case (RPO NP1)
Supercede:
This bulletin is being revised to add the 2012 model year and update information. Please discard Corporate Bulletin Number 04-04-21-002C (Section 04 - Driveline/Axle).
Some customers may comment on a grind noise or a bump/clunk felt when shifting the transfer case into 4LO or 4HI. Also some customers may comment on a grind or bump feel shifting the transfer case out of Neutral.
- The grind/bump/clunk felt when the transfer case electrically shifts into 4HI/4LO out of neutral is due to the engagement sequence that applies engine torque through the transfer case, front differential and front axles.
- The noise, present in all electronically shifted 4WD systems, is considered normal operation and does not pose any potential to impart damage by shifting into 4HI/4LO out of neutral.
- The noise level in the Colorado and Canyon is louder than in larger vehicles due to the vehicle size and transfer case design.
- The noise level can be reduced by following the Owners Manual Instruction of shifting while in neutral and in forward motion of about 4 km/h (3 mph).
- Alternatively, the noise can be eliminated by shifting into or out of 4LO/ Neutral with the key on and engine off.
- DO NOT REPLACE the transfer case in an attempt to repair this condition.
- DO NOT attempt to make repairs to the transfer case at this time for this condition.
- DO NOT attempt to reprogram the transfer case control module (TCCM). The TCCM is NOT REPROGRAMMABLE on this vehicle.
- DO NOT replace the TCCM in an attempt to repair this condition.
- DO NOT replace the transfer case actuator in an attempt to repair this condition.
- General Motors encourages dealers to share this information with concerned customers.
Disclaimer