A transfer case is a part of your vehicle's drivetrain that connects your transmission to the differentials. It's also known as a transmission-to-axle or T/A. This makes it possible for your four-wheel drive vehicle to handle complicated terrains with ease.
The transfer case transfers engine power from the transmission to the front and rear differentials. It does this by engaging one of two differentials, depending on the torque requirements of each axle. This is helpful when moving around corners or climbing up or downhills. The transfer case contains gears and clutches to switch between differentials at high speeds and high torque loads.
When you're operating a standard car without any modifications, your vehicle operates in two-wheel drive mode. When you need more traction than two wheels can provide, simply press on your accelerator pedal to engage four-wheel drive mode and get an extra grip on the road!