This is a problem...
Today I was working on fixing the driveline vibration and finally got
around to hopefully fixing the diff lock. The diff lock has never worked
since I got this van, but when I had the transmission out tested it with a
hand vaccuum pump and it locked well.
I was missing a short piece of hose from the "main hose" that runs along
the frame rail to the blue check valve going into the "Balls". I installed
a piece of hose. Without turning the diff lock knob or anything, the
transmission locked when I started the engine and a few attempts at driving
(about twenty feet) confirmed that it's definately locked. I don't want to
drive it again and damage anything, and I want to get it disengaged, even
if i can't get it "working" to relock.

I took the check valve off just to relieve the vaccuum and sure enough, it
hissed upon release. This seemed like it should have fixed it, but alas,
still locked. Does it require vaccuum to "UNLOCK" or just to lock and lack
of vaccuum unlocks it?

Perhaps my hoses are just swaped at the lock actuator?

-Craig
'87 Sunroof Syncro