88 GMC front output flange

[lugnut]

Does anyone know what size socket the front output shaft nut takes? This is where the front driveshaft bolts up to the transfer case. It is a square flange, with four bolts that hold the driveshaft on. I need to replace the seal, but dont have a socket big enough to fit the nut, I need to pick one up on the way home but want to know what size it is before I just start guessing and buying every socket bigger than 1-1/16...thanks.