As you may already know, the latch  mechanism is at the rear of the door.  You may need to have the  latch moved out (away from van) just a "smudge" to make it latch easier when the door get slammed. If you moved it out too much than you'll get the opposit effect, ie you'll have to slam the door real hard to make it latch.
 If that adjustment don't do it, then, the back of the door may be hanging too high or too low. Peek into the latch when you slide the door close gently and see where the latch is hitting the catch.  It should be centered.  The only adjustment is the travel wheel mechanism at the bottom front of the door. Loosen the bolts slightly to adjust the height of the hang.  Lower the front to lift the back and raise the front to lower the back.  It takes patiences and trial and error.   I seem to have to adjustment mine once very 3 years or so.

Yau-Man Chan
87 GL

>>> Mike Blair <mblair0322@YAHOO.COM> 12/31 8:00 AM >>>
I have an 86 and 87 gl and they both are having the same problem. If
the sliding door is closed with any force (I had an 83 that required
force to close) there is something that is, apparently misaligned and
the door won't close. If you close it gently it closes. I have also
had the door on the 86 come open when I was driving. My guess is that
it wasn't really latched, but it appeared to be. Any suggestions will
be greatly appreciated. I am planning on working on this on this
Saturday, 1/2/99. Again, thanks for the help.

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