Whether you know it or not, a single automotive component is responsible for turning a two-wheel drive vehicle into an all-wheel drive one. Attached to the transmission, as well as the front and rear axles, the transfer case lets you engage power to all four wheels when you need it, then switch back to only two wheels for normal driving conditions. Like most transmission system components, the transfer case must withstand an incredible amount of stress as it transmits the engine’s power to the drive shaft. As such, there’s always a chance something could go wrong. Here are the most common problems drivers experience.
Low Transmission Fluid
Because it is separate from the transmission case, the transfer case needs its own transmission fluid. In addition to cooling the moving metal parts, the fluid also lubricates the chains or gears that transmit power from the engine to the drive shaft on the front or rear axles. If the fluid level is too low, the box can easily overheat, causing parts and components to seize up. In extreme instances, it may not be possible to shift between the two drive modes at all. Although adding fluid should solve the problem, it will not undo any wear and tear that was caused by inadequate lubrication.
Bad Vacuum Line
The component that actually changes the linkages from two to four-wheel drive and back again is called the vacuum line. Because it relies on pneumatics, the line may not have the power it needs to operate the mechanism and change the gears if it has a fluid leak. To check for a leak, simply listen to the engine as it runs. If you hear a hissing sound, it probably means the line is leaking.
Worn Transfer Chain
Most four-wheel drive vehicles rely on a chain to transmit power from the motor to either or both drive shafts. Just as with a bicycle, this chain has gears and sprockets that allow it to switch between gears. Because they must endure an enormous almost of stress and strain while moving power, these chains can stretch or break. When this occurs, the component will no longer fit on the sprockets and gears it uses to transmit power. In extreme cases, the problem may lead to total transmission failure. More often than not, however, drivers will experience surefire signs of transmission issues such as stalling and gear changing delays. The only repair option for a worn or broken chain is replacement.
Transfer Case Damage
As tough and durable as they may be, transfer cases were not designed to withstand direct damage from road materials. Rocks and other road hazards can easily smash the vulnerable box, causing it to leak transmission fluid. When this happen, the components inside may seize up and prevent shifting between the two modes. If the chain, sprockets, and other components are undamaged, simply replacing the case and adding fluid should solve the problem. However, when the mechanism itself is harmed, repair costs could be considerable.
If you are experiencing any of the aforementioned problems, take your vehicle to a professional mechanic as soon as possible.