What is this line on the transmission?
 

I'm pullng the engine and transmission on my 1980 116 300SD. I have most stuff detached but I can't seem to figure out what this line (*see pics) is and or what it does. It looks like a hose of some sort coming from under the driver's seat area and attaching to the side of the tranny near the drivers side of the drive shaft.

ps- It's not the tranny cooler lines. They are in the front and I have already disconnected them from the radiator.

Thanks!
-Ryan

Is the other end connected to the speedometer?

Speedo cable-

Yep. Thanks. I've got everything disconnected and am hooking up the hoist to the engine right now.