I use just the gasket, but rtv, gasket, pretty much any combo will work. While you have it apart you prolly should go ahead and change the input seal on the transfer case. You can take a small screwdriver and move the rubber a little, if it cracks change it, if it moves softly its ok. If it leaks, it will leak transmission fluid into the transfer case and you won't really realize it because it won't leak onto the ground until the transfer case vents it out.