Good question LOL. I debated while the housing was taken apart putting in a drain, but I figured that the diff would very rarely ever come back out so it wasn’t that big of a deal. Plus, I’m an off road guy, so my way of thinking is that you don’t want anything hanging off the bottom of the diff to get caught on anything. I guess cars don’t really have that problem..... my bad lol. Now that you have me thinking about this, I might just add one offset to the side a little so that it drains below the flange and less mess when removing the diff.
