Transfer Case Clunk in 4HI

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Cause	Correction
DEFINITION: During acceleration or deceleration, a clunk is heard or felt in the transfer case while in the 4HI range only. Review the Symptoms - Transfer Case and perform the necessary inspections.
Incorrect fluid level or incorrect fluid	Inspect the transfer case for the correct fluid level. Refer to Transfer Case Fluid Replacement . Inspect the transfer case for the correct type of fluid. Flush the transfer case and fill with the correct fluid, if required. Refer to Transfer Case Fluid Replacement .
Input gear thrust washers	Inspect for worn or missing input gear thrust washers. Refer to Cleaning and Inspection in Transfer Case - NVG 261-NP2 Unit Repair. Replace the thrust washers as required. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 261-NP2 Unit Repair.
2/4 Wheel drive synchronizer assembly	Inspect the synchronizer for the following conditions: The synchronizer hub internal teeth to rear output shaft splines for excessive looseness caused by wear The synchronizer sleeve engagement teeth to the synchronizer gear for wear Refer to Cleaning and Inspection in Transfer Case - NVG 261-NP2 Unit Repair. Replace the synchronizer assembly if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 261-NP2 Unit Repair.
Rear output shaft bearing outer retaining ring	Inspect for the following conditions: Proper installation of the rear output shaft bearing retaining ring Excessive wear or damaged retaining ring groove in the rear case half Repair or replace the following components if faulty: Properly install a new rear output shaft bearing outer retaining ring. Replace the rear case half if the retaining ring groove is excessively worn. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 261-NP2 Unit Repair.
Worn high speed teeth on the range sleeve	Inspect for worn high speed teeth on the range sleeve. Refer to Cleaning and Inspection in Transfer Case - NVG 261-NP2 Unit Repair. Replace the range sleeve if worn. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 261-NP2 Unit Repair.