The heart of any All Wheel Drive (AWD) or Four Wheel Drive (4x4) vehicle is a component called a Transfer case. The Transfer case takes the power leaving the rear of the transission and splits it into 2 separate outputs. The transfer case on the vast majority of vehicles is a separate component from the transmission.
One output drives the front axles, the other output drives the rear axle. On most vehicles today, this torque is evenly divided as the Powertrain Control Module (PCM) sees fit. There are many inputs into the PCM that allows the PCM to split the torque in the most efficient manor and maximum traction.This method of having a computer make decisions on the torque split of the transfer case is sometimes referred to as an "On-demand" transfer case.This torque split happens seamlessly, and imperceptibly to the driver...until its needed.
Sadly, our experience has been that most drivers don't know if their AWD or 4x4 system is not working until they get in a driving situation where it is imperative for that system to work. If the system doesn't work, a stuck vehicle is often the result and its never at a convenient time or place. This is why a large percentage of AWD and 4x4 transfer case system repairs end up being towed into our shop.
The good news is that most repairs never need a new transfer case. We have found that the most common problem with today's transfer case is with the electrical system that operates it. Many times it is a switch, sensor or most often, the electrical shift motor to the transfer case is not working. All of these electrical problems are repairable in the vehicle, without major expense.
When transfer case problems do turn out to be more serious, its extremely common for us to find the factory fluid still in the transfer case, few drivers know about routinely changing the transfer case lubricant. Most transfer cases require special lubricant, some, only the factory will work. It takes an expert to know the difference. We've been fixing transfer case problems for over 45 years and we know the solution to keep it fixed right!