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 components for being faulty. Refer to Transfer Case 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.
  3. Inspect the synchronizer for being faulty.
  4. Replace the synchronizer, if faulty. Refer to Transfer Case Assemble.

High/low range shift fork assembly

  1. Inspect the high/low shift fork assembly for the following conditions:
  2. • The roller on the shift block for wear or damage
    • Shift shaft spring broken
    • Worn or melted range fork pads
    • Bent shift shaft
    • Cracked or bent shift fork
  3. Replace the high/low shift fork assembly, if found faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble.

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 rear output shaft
    • 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.

Rear output shaft front support bearing

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

Planetary carrier low gear

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

2/4 wheel drive shift fork assembly

  1. Inspect the 2/4 wheel drive shift fork assembly for the following conditions:
  2. • The roller on the shift block for wear or damage
    • Shift shaft spring broken
    • Bent shift shaft
    • Worn shift fork pads
    • Cracked or bent shift fork
  3. Replace the 2/4 wheel drive shift fork assembly, if found faulty.
  4. Refer to Transfer Case Disassemble and Transfer Case Assemble.

Control actuator cam

  1. Inspect for the following conditions:
  2. • The control actuator cam at the shift fork cams for being worn
    • The bushing for the control actuator cam shaft for being worn
  3. Replace the following components, if found faulty:
  4. • The control actuator cam
    • The bushing for the control actuator shaft

Drive sprocket

  1. Inspect for the following conditions:
  2. • Synchronizer engagement teeth on the drive sprocket for burrs or damage
    • Worn bushing in the drive sprocket
    • Journal on the rear output shaft for excessive wear or damage
  3. Replace the drive sprocket if it is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble.
  4. Replace the rear output shaft if it is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble.