still foolin with the 4WD

I have a 96 S-10 blazer with the 4WD not working. When i push the button to engage it, i hear what sounds like the hubs locking but there is no wheel spinning. Now since my last post (pretty much like this post) i started really tearing into it and seeing if i can find out what the problem is. Now so far I have checked the the vacuum line that goes to the the mechanism that has the cable that attaches to the transfer case. Now, what I have done was unplug that line from the spider before it and just put my finger over the hole. The vacuum feels very weak. I sucked on the line myself that pulls that cable and it seems like it needs a lot of air to do anything to it. Once, it does react though it seems like it needs little to no air to keep it engaged. With the engine off i sucked on the line that returns back to the engine and there seems to be pretty good resistance, and i didn't really hear any leaking. Now I'm completely lost. Is it possible for that mechanism to go out or does it normally need a lot of vacuum to engage it? Or am I completely missing something? Any help would be greatly appreciated.

Have you went threw this link?
Is the front axel actuator getting good engine vacuum?
Check for vacuum with a vacuum gauge.
http://www.automotiveforums.com/vbulletin/showthread.php?t=572914

My sister had a 1993 blazer that did that and it turned out to be something in her switch itself grounding out. You might give that a try.

so do you know off hand what the vacuum should read? also, with the actuator it seems to need a lot of air moving fast to engage it, is that normal?

18 or more 20 is better or should read full engine vacuum.
Also check vacuum hoses for transmission fluid.
Vacuum Switch on transfer case should switch vacuum to it when in 4W.