Transfer Case Clunk in 4LO Lock

WARNING: This page is about a different car, the 2007 Hummer H2. 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 4LO Lock range only. Review the Symptoms - Transfer Case and perform the necessary inspections.
High/low planetary carrier assembly	Inspect for the following conditions: Excessively worn planetary gears The planetary gears loose in the planetary carrier The input gear for missing thrust washers or excessive thrust end play in the carrier Excessively worn range sleeve engagement teeth on the carrier Refer to Cleaning and Inspection . Replace the high/low planetary if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Annulus gear	Inspect the annulus gear to front case fit for excessive looseness. Inspect the front case for wear caused by excessive looseness. Replace the front case half if it is worn.
Range sleeve	Inspect the range sleeve engagement teeth for excessive wear. Inspect the range sleeve to mainshaft splines for excessive wear. Replace the range sleeve if it is faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble .