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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1613 (Transfer Case - NVG 149-NP (One Speed Automatic)) >> Diagnostic Information and Procedures >> Transfer Case Viscous Coupling Test >> Tools Required

Tools Required

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

J 45382  Transfer Case Tester

To determine if the viscous coupling is operating correctly, use the following test procedure. Testing the viscous coupling operation by removing a propeller shaft and driving the vehicle will cause the viscous coupling to fail. The test will determine if the viscous coupling is faulty from a totally locked up failure, or if the viscous coupling fluid has leaked out from being severely humped.

Fig 1: Testing Viscous Coupling Operation Using J 45382
G01481016Courtesy of GENERAL MOTORS CORP.
IMPORTANT: The Viscous Coupling Test is very sensitive to the temperature of the transfer case. If the transfer case is very hot, the time to turn will be faster. If the transfer case is cold, the time to turn will be slower.
  1. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
  2. Set the parking brakes for the rear wheels.
  3. Position the transmission in NEUTRAL.
  4. Raise the vehicle. Refer to JACKING AND LIFTING .
  5. Remove the front propeller shaft. Refer to PROPELLER SHAFT REPLACEMENT-FRONT  .
  6. Install the J 45382  into the transfer case front output shaft.
  7. Using a torque wrench at 11 N.m (100 lb in) on the J 45382,  turn the front output shaft 90 degrees.
  8. Note the length of time it takes to turn the front output shaft the 90 degrees.
    • If the front output shaft turns slow, and takes at least 10 seconds, the viscous coupling is operating correctly.
    • If the front output shaft will not turn, the viscous coupling or the planetary carrier assembly could be locked-up.
    • If the front output shaft turns easily, and the 11 N.m (100 lb in) cannot be obtained, the viscous coupling is faulty.