Extra hole on transfer case?

[Wrath]

So now I'm working on my lady's 97 XLT, about to pull and rebuild the transmission. I got the transfer case out last night and noticed there's an extra hole in the front half of the case; drivers side around the corner from the breather hose. This hole is not present on my Limited's transfer case, and there was nothing connected to this one. Any ideas what it is? I suspect that it is the reason the t-case is covered with a baked-on layer of grease/oil.

 

[410Fortune]

I have never seen that hole before it looks like it was added. Yes fluid can push out if there and worse water can get in

 

[Wrath]

I've never seen one there either, and I hadn't found any info on it. I might see about cleaning it out and sealing it if I can't find any info on what it's for. If there were two holes I'd suspect someone had put an external cooler on it at some point.

 

[Wrath]

Finally got some nicer weather so I can resume this project. Got a pressure washer and cleaned things up real nice.
Discovered that this transmission has indeed been worked on before. There was a rebuild tag siliconed to the casing. And it had been spray painted with a non high-temp paint. Wire brushed all that off last night. Cracked open the oil pan this morning, and unless I'm mistaken this control valve body has already been modded/TSB'd?

 

[Wrath]

In particular I'm looking at this.

 

[Wrath]

ATSG manual says to throw these out and use new ones. But they weren't tight enough to be TTY bolts, so is it just the cheap rubber o-rings that got crushed? If so I have some nice green HNBR replacements. Anyone know?

 

[Wrath]

Update: The Hole as it turns out is a GNDN.
(Goes Nowhere, Does Nothing).
Maybe an optional mounting point for something? What I thought was a washer impression actually looks now more like the shape of the casting. No outlet at the bottom, no threads. Just a smooth-walled bore.