I service my Tcase at the same interval as the transmission which for me would be somewhere around 30K. I don't remember the capacity, but it's in your owner's manual. Just remove the bottom plug on the rear of the Tcase to drain it. Then put that plug back and remove the top on. I think they are 10mm hex. Fill to overflow on level ground. If you have a leveling kit, you may want to top it off with the back raised slightly to help you get the factory fill line. I like to use a suction gun to install the WalMart DexIII that I use in mine.