Man, it must be cold where you guys live with all this oil pre-heating! I just cut the tip off a bottle of standard 80w90 gear oil and lift it up and jam the end into the factory hole and squeeze the bottle until it is empty. Repeat with a second bottle until it starts running out the hole. I put in a bottle of the GM posi additive before I start putting the gear oil in. I forgot the additive one time and the posi was making some noise. Noise was most evident when backing up while turning to get out of the driveway.