Transfer case fluid lubricates and removes heat from internal components in the transfer case. A transfer case fluid replacement is needed in order to maintain the fluid's lubrication ability. Most manufacturer's recommend that the transfer case fluid be replaced every 30,000 miles. with either conventional or synthetic gear oil. However, some manufacturer's may vary on their recommendations, so advise your vehicle's owners manual to determine when a transfer case fluid replacement is needed and what kind of fluid to use.
When performing a transfer case fluid replacement, it is best to have the vehicle up to normal operating temperature before draining the fluid. Then the technician raises the vehicle on a hoist and removes the transfer case drain plug to drain the fluid. Sometimes there is a magnet on the drain plug that catches any suspended metal particles. If there is a magnet, then it should be cleaned off. Finally, the correct amount of new fluid is put into the transfer case and the level is checked.
Since a transfer case fluid replacement is often part of the scheduled maintenance of your vehicle, you would be best advised to follow the factory recommended vehicle maintenance schedule for how frequently to replace the transfer case fluid. This factory recommendation must be adhered by to maintain the validity of your new car warranty and extended auto warranty, if applied. If mechanical breakdown occurs due to the lack of your car's maintenance of the engine oil and filter, the warranty would not cover the car repair.