Transfer Case Clunk in 4HI

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 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. Inspect the transfer case for the correct type of fluid. Refer to Approximate Fluid Capacities . Flush the transfer case and fill with the correct fluid, if required. Refer to Transfer Case Fluid Replacement .
Input shaft thrust washers	Inspect for worn or missing input shaft thrust washers. Replace the thrust washers as required. Refer to Transfer Case Disassemble and Transfer Case Assemble .
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 drive sprocket for wear Refer to Two/Four Wheel Drive Shift Components Cleaning and Inspection . Replace the synchronizer assembly if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Rear output shaft rear bearing outer retaining ring	Inspect for the following conditions: Properly installed rear output shaft rear bearing outer retaining ring Excessive wear or damaged retaining ring groove in the rear case half Repair or replace the following components if found faulty: Properly install a new rear output shaft rear 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 .
Worn high speed teeth on the high/low clutch	Inspect for worn high speed teeth on the high/low clutch. Refer to High/Low Shift Components Cleaning and Inspection . Replace the high/low clutch if worn. Refer to Transfer Case Disassemble and Transfer Case Assemble .