Front Wheels Slipping with Vehicle in Four Wheel Drive (Replace Transfer Case Clutch Plates and Front Drive Axle Lubricant)

This bulletin is being revised to correct two part numbers in the Parts Information section. Please discard Corporate Bulletin Number 99-04-21-003B (Section 04 -- Driveline/Axle).

Some owners may comment on a slipping type condition at the front wheels while the vehicle is in four wheel drive (4WD).

When the vehicle is driven extensively in low temperatures (-12°C (10°F) or below), slipping may occur when the vehicle is in the 2 HI mode. This occurs because the transfer case clutch pack does not have enough torque capacity to overcome the viscosity of the front axle lubricant. The friction generated by the slipping clutch discs may cause premature wear of the clutch pack assembly.

Overhaul the transfer case and replace the clutch plates on affected vehicles. Replace the lubricant in the front drive axle with synthetic axle lubricant, P/N 12378261 (Canadian P/N 10953455). Use the following procedure and the part numbers listed below.

1. Remove the transfer case drain plug. If the plug is difficult to remove or stripped, refer to Corporate Bulletin Number 99-04-21-001.
2. Drain the fluid from the transfer case. Refer to the Transfer Case sub-section of the applicable Service Manual.
3. Remove the transfer case assembly from the vehicle. Refer to the Transfer Case sub-section of the applicable Service Manual.

Important: The NV236 transfer case (T Models) uses 8 friction and 7 steel plates. The NV246 transfer case (K Models) uses 10 friction and 9 steel plates.

4. Overhaul the transfer case and replace the clutch plates. Refer to the applicable Transmission/Transaxle and Transfer Case Unit Repair Manual.
5. Install the transfer case assembly into the vehicle. Refer to the Transfer Case sub-section of the applicable Service Manual.
6. Install the transfer case drain plug.

Tighten
Tighten the drain plug to 20 N·m (15 lb ft).

Important: Do not use standard DEXRON® lll fluid. Performance of the transfer case may be impaired.

7. Remove the transfer case fill plug. If the plug is difficult to remove or stripped, refer to Corporate Bulletin Number 99-04-21-001.
8. Fill the transfer case with 1.9 L (2 qts) of Automatic (AUTO- TRAK ll) Transfer Case fluid, P/N 12378508 (Canadian P/N 10953626).
9. Install the transfer case fill plug.

Tighten
Tighten the fill plug to 20 N·m (15 lb ft).

10. Change the front drive axle lubricant to synthetic axle lubricant, P/N 12378261 (Canadian P/N 10953455). Fill the drive axle with 1.66 L (1.76 qts) for K Truck or 1.20 L (1.27 qts) for T Truck. Refer to the Front Drive Axle sub-section of the applicable Service Manual.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: