How are Transfer Case Assembly issues diagnosed?
Transfer case issues on modern vehicles are obvious as a scanner will identify fault codes related to the issue. The vehicle may drive normally in most instances, so the issue may have to be replicated through driving to determine the cause of the fault. When a transfer case is obviously mechanically damaged, it must be removed, disassembled, checked against specifications, and diagnosed as repairable or not.

How are Transfer Case Assemblies replaced?
When the transfer case has failed, it must be removed by, first, draining the oil from the transfer case, removing the driveshafts, and disconnecting the transfer case input from the transmission output shaft. Electronic connections must be removed, and the transfer case will be supported by a transmission jack before removing the transfer case mounting bolts. Replacement is the reverse of removal, and the driveshaft universal joints, transmission output shaft seal, and, if equipped, coupler will be inspected and replaced if necessary. Finally, the transfer case is filled to specification with the appropriate fluid.
RepairPal Recommendations for Transfer Case Assembly issues
Even if a transfer case issue does not cause complete failure, the vehicle should be placed out of service. This is to protect the transfer case from further damage, and provide safety for the intended occupants. If the transfer case fails during operation, the vehicle may be left permanently in neutral or the transfer case may bind. If the transfer case is malfunctioning electronically it can cause erratic shifts from high to low gear and from two-wheel drive to four-wheel drive. Either situation can cause a dangerous situation while driving.
What to look out for when dealing with Transfer Case Assembly issues
Many models of vehicle, even from the same model year, will use a different transfer case than another vehicle of the same type. This is due to differences in gear ratios, engine power, and intended use for the vehicle. Before replacing a transfer case, ensure that the proper part number is ordered to avoid incompatibility.
Can I replace the Transfer Case Assembly myself?
Transfer case replacement is a large job, but a straightforward job. The biggest issue to overcome is how to remove and install the transfer case, as transfer cases can be very heavy. Diagnosing a transfer case is not typically a difficult task, but if the electronic operation of the transfer case is not understood, the transfer case may be replaced for a minor electronic issue.