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Home >> GMC >> 2021 >> Terrain SL >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Power Transfer Unit/Transfer Case - AAM) >> Diagnostic Information and Procedures >> Constant Noise

Constant Noise

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Cause Correction
Inspect for the proper transaxle and gear oil levels prior to performing system diagnosis.
Low gear oil level Inspect the power transfer unit for leaks, repair as required.
Refer to Power Transfer Unit Case Leak Diagnosis , or Adhesives, Fluids, Lubricants, and Sealers .
Incorrect gear oil in the power transfer unit Replace the gear oil.
Refer to Adhesives, Fluids, Lubricants, and Sealers .
Worn propeller shaft constant velocity joints Replace propeller shaft assembly.
Refer to Two-Piece Propeller Shaft Replacement .
Bearing noise within the power transfer unit
  • A grinding noise that occurs at a specific engine speed, regardless of transmission gear, is not within the power transfer unit.
  • A grinding noise that changes as a transmission shift occurs is not within the power transfer unit.
  • A grinding noise that changes as vehicle speed changes may be also caused by worn wheel bearings.
  • A grinding noise that changes as the vehicle turns may also be caused by worn wheel bearings and/or tires.
  1. Inspect for the proper power transfer unit fluid level. Fill, as required.
  2. Identify the location of the noise using the J-39570  Chassis Ears.
  3. If the noise continues, inspect the power transfer unit internal components. If damage is present, replace the assembly as required.
Gear set whine noise within the power transfer unit
  • A whine noise that occurs at a specific engine speed, regardless of transmission gear, is not within the power transfer unit.
  • A whine noise that changes as a transmission shift occurs is not within the power transfer unit.
  • A whine noise that changes as vehicle speed changes may be also caused by worn wheel bearings.
  • A whine noise that changes as the vehicle turns may also be caused by worn wheel bearings and/or tires.
  1. Inspect for the proper power transfer unit fluid level. Fill, as required.
  2. Identify the location of the noise using the J-39570  Chassis Ears.
  3. If the noise continues, inspect the power transfer unit internal components. If damage is present, replace the assembly as required.
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