I read my manual regarding maintenance, and it says if I towed while the truck was new, to change the rear differential oil at 3750miles. I can do this myself, except for Nissan putting a huge torx head bolt with a hole in the center, instead of just using a regular bolt/drainplug. Anyone know what size torx socket it takes and where I could order one??? The dealer wanted $110 to change a couple quarts of gear oil!!