According to the service book, the oil in the transfer case must be changed every 45,000 km. mileage.
You will need: a 12 mm Allen key, a syringe for filling transmission units, and a container for used oil.
It is more convenient to perform this operation on an inspection pit or on a lift.
It is recommended to drain the oil immediately after the trip, while the transfer case has not cooled down and the oil has good fluidity.

Using a hex key "on 12" unscrew the plug

Drain the oil.
After cleaning the magnet, tighten the drain plug.

Using a 12 mm Allen key, unscrew the filler plug

Fill in the oil with a syringe.
You can fill in the oil with a supercharger

Check the oil level - it should reach the lower edge of the filler hole.

Clean the breather located on the side of the rear propeller shaft (shown on the removed transfer case) from dirt