GM Service Manual Online
For 1990-2009 cars only

Cause

Correction

DEFINITION: While shifting from HI range to LO range, there is gear clashing or no HI range; or the transfer case will not shift from 2 wheel drive to 4 wheel drive.

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

Mode block

  1. Disassemble the transfer case. Refer to Transfer Case Disassemble .
  2. Inspect the synchronizer sleeve for sliding freely on the synchronizer hub.
  3. Inspect the synchronizer sleeve for being faulty.
  4. Replace the synchronizer sleeve if faulty. Refer to Transfer Case Assemble .

If the symptoms occur during cold temperatures, flush and fill the front axle with synthetic fluid. Refer to Front Axle Lubricant Replacement .

High/low range shift fork

  1. Inspect the high/low shift fork for the following conditions:
  2. • The shaft on the shift fork for wear or damage
    • Worn or broken range fork pads
    • Cracked or bent shift fork
  3. Replace the following components if found faulty:
  4. • The shift fork pads
    • The shift fork

High/low range sleeve

  1. Inspect the high/low range sleeve for the following conditions:
  2. • Engagement teeth for burrs or damage
    • Sliding freely on the mainshaft
    • The range sleeve shift fork collar for excessive wear
  3. Replace the range sleeve if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble .

Input gear needle bearing

  1. Inspect for the following conditions:
  2. • Failed needle bearing in the input gear
    • Journal on the mainshaft for excessive wear or damage
  3. Replace the bearing if faulty.
  4. Replace the mainshaft if damaged.

High/low planetary carrier

  1. Inspect the high/low planetary engagement teeth for burrs or damage. Refer to Transfer Case Cleaning and Inspection .
  2. Replace the high/low planetary carrier if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble .