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 shift clash

  1. Disassemble the transfer case. Refer to Transfer Case Disassemble .
  2. Inspect the synchronizer for being faulty. Refer to Two/Four Wheel Drive Shift Components Cleaning and Inspection .
  3. Replace the synchronizer if faulty. Refer to Transfer Case Assemble .

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 or synchronizer hub for being faulty.
  4. Replace the synchronizer sleeve or synchronizer hub 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 Level Inspection .

High/low shift fork spring assembly

  1. Inspect the high/low shift fork spring assembly for the following conditions:
  2. • Worn high/low shift fork pin
    • Worn cam
    • Broken spring
  3. Replace the following components if found faulty:
  4. • The high/low shift fork spring assembly
    • The high/low shift fork pin

High/low shift fork

  1. Inspect the high/low shift fork for the following conditions:
  2. • Worn shift 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 clutch

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

Input shaft pilot bearing assembly

  1. Inspect for the following conditions:
  2. • Failed input shaft pilot bearing in the input shaft
    • Journal on the rear output shaft for excessive wear or damage
  3. Replace the bearing if faulty. Refer to Input Shaft Pilot Bearing Replacement .
  4. Replace the rear output shaft if damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble .

High/low planetary carrier assembly

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