GM Service Manual Online
For 1990-2009 cars only

Cause

Correction

DEFINITION: A faulty internal transfer case component that causes a growl or grinding noise in the transfer case while the vehicle is turning or in a four wheel drive mode.

Review the Symptoms - Transfer Case and perform the necessary inspections.

High/low planetary carrier assembly

  1. Inspect the high/low planetary carrier pinion gears for the following conditions:
  2. • Chipped, bent or deformed teeth
    • Pinion gear bushings worn
    • Pinion gear thrust washers missing
    • Seized or binding pinion gears
    • Refer to Transfer Case Cleaning and Inspection in Transfer Case - NVG 236-NP8 Unit Repair.
  3. Replace the high/low planetary carrier assembly if any of the above conditions exist. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Annulus gear

  1. Inspect the annulus gear for teeth damage or wear. Refer to Transfer Case Cleaning and Inspection in Transfer Case - NVG 236-NP8 Unit Repair.
  2. Replace the front case half if the annulus gear is faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Input gear

  1. Inspect the input gear in the planetary carrier assembly for excessive thrust end play. Refer to Transfer Case Cleaning and Inspection in Transfer Case - NVG 236-NP8 Unit Repair.
  2. Inspect the input gear teeth for the following conditions:
  3. • Gear tooth failure
    • Worn or galled thrust surfaces
    • Refer to Transfer Case Cleaning and Inspection in Transfer Case - NVG 236-NP8 Unit Repair.
  4. Replace the input gear if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Thrust washers

  1. Inspect the thrust washers for being broken or missing.
  2. Inspect the thrust washers for galling.
  3. Replace the thrust washers if faulty and the mating component if damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.