1997 blazer vaccuum

I have read several posts and everyone seems to call the vaccuum controller under the battery for the 4x4 the "vaccuum thingy". what is this really called so I can buy a new one. I bought a truck with this piece missing. 1997 chevy blazer 2door.
Thanks.

I have read several posts and everyone seems to call the vaccuum controller under the battery for the 4x4 the "vaccuum thingy". what is this really called so I can buy a new one. I bought a truck with this piece missing. 1997 chevy blazer 2door.
Thanks.

http://www.automotiveforums.com/vbulletin/showthread.php?t=572914