General Mechanical Diagnosis

Transfer Case Diagnosis:

1. Road test the vehicle to verify the problem, noting road speed, engine speed, and speed range where the vehicle problem is evident.

NOTE: Owner driving habits as well as road and weather conditions should be noted.

2. Raise the vehicle on a hoist and position suitable safety floor stands under the vehicle.
3. Run the vehicle at the road speed and in the axle drive mode (4WD/2WD) where problem exists. Verify problem area:
a. Engine
b. Clutch/Transmission
c. Transfer Case
d. Front/Rear Driveline Components
e. Front/Rear Drive Axles
f. Front/Rear Brake Systems
g. Front Axle Locking Hubs
h. Front/Rear Wheels and/or Tires

NOTE: If the problem area is indicated to be other than the transfer case, refer to the appropriate system.

4. Refer to the appropriate owner's guide for operating data if the problem is verified to be driveline or torsional windup, before servicing the transfer case assembly.

Points of Possible Slippage, Four-Wheel Drive:

5. If the 4WD system slips under load, find what has broken or is slipping. To locate where slip is taking place, put marks at various possible slip points. Test drive the vehicle, then check to see if marks at different points are still in the same relationship to each other. This will indicate where the slippage is taking place or where to look for broken parts, if any.
a. On vehicles with auto hubs, find a suitable place where the vehicle can be tested. Mark the components, then drive vehicle without backing up. Stop and check the marks to see if they are in the same relationship to each other. If the vehicle is backed up before checking these marks, the hubs may re-index and not reveal the problem.
6. Check tires and vehicle loading if the problem is clearly driveline windup and not broken parts.
7. If the transfer case shift control motor operates properly and nothing happens, or if a manual shift lever fails to shift the transfer case it will have to be serviced. Be sure driveline windup has been eliminated as a cause.
8. Driveline noise may be experienced if a vehicle is operated in 2WD with the hubs locked. This occurs because the 4WD components are in motion instead of at rest (the normal condition in 2WD with the hubs unlocked). However, it is important to remember that excessive noise may be a sign of a serious problem.

Maintenance of the hubs is important. Easy shifting from one operating position to the other requires smooth movement of the inner clutch ring. This ring slides on splines which must be clean and well lubricated. To prevent dirt and water from entering the hub unit, the oil seals must be very carefully installed. If the vehicle is operated where the hub is constantly submerged in water or mud, the hubs should be serviced more frequently. The important thing is not to run for long periods with dirt and water in the hubs. Start with a short service interval and check for water and dirt. Stretch out the interval as experience shows how dirty they are actually getting.