> I found it finally, under the van 2/3 of the way back on the drivers side. 
> There is this plastic module that looks like three sphere put together.  A
> wire or vacuum tube comes out of the back and goes into this "y" junction. 
> One of the tube/wires goes off into a harness and the other goes into this
> short cylinder thing.  It is the shape of a short, sqaut c size battery and
> then out of ther back of that a tube/wire goes into the harness.
> 
> Well this little cylinder is humming away and annoying as hell!  It doesn't
> seem to affect the engine performance, but when I was playing with it it idle
> change a little.
> 
> Question:  What is this thing?  Is it suppossed to hum?  Should I replace it?
> 
> Help, please! Thanks,
> 
>          - Craig
> 
Wow.  I don't have this on *my* syncro, so you can take all those bits off and put
'em in a box, and send 'em to me!

This plastic dohicky sounds like the vacuum storage unit for your diff lock (I take
it you have a diff lock -- I don't).  It is leaking.  You really need to block off
the vacuum hose from the engine until this thing is replaced, but you will lose your
diff lock until then, too.  You can try to find the leak and try and fix it, but I
have had little success in the past.  A similar canister is used on diesels for the 
brake booster, so you might be able to snag something that will work from an old
diesel rabbit.  Or maybe VW has a decent price for new one (snicker, snicker).

Actually, you never can tell.  VW has the occasional part priced reasonably.

Since I don't have a diff lock, nor have ever actually looked at one, I could be
completely wrong on this -- it's all guesswork!

malcolm