You really have to stare at the door and shut it a few times to figure out what's going on. If the door raises up a little bit when it shuts, whether you have the plastic bushing or not, the hinges are worn. Of course the "right" thing to do is replace the bushings, but a quick way to raise the door up is to loosen the lower hinge bolts on the door and install some thin washers. I have tried to loosen the other bolts so I would not have to use washers but they are very tight, and I have broken a couple of ratchets trying to get them loose. There is not much room in there.
Once I got the door shutting without the pin raising it up, it would still not shut sometimes and bounce back out about a 1/2 inch. When I found out about the plastic missing, I installed the pex over the pin and the door quit doing the bounce-back problem and shut on the first try every time.
On a another truck I had, the door rattled terribly when going over bumps. I had the door all adjusted up and it still did it. The frame crossmembers were starting to rust out bad so I went to the junkyard and got the back half of a better frame, drilled out all the rivets, and installed them in my truck. That's when I found out on the "good" donor, the brace right under the cab mount donut had rusted out a perfect hole right under the rubber. When I took mine out I found the same thing, so I had to patch the donor brace before I installed it. After I did all this I realized a bonus; No more door rattle over bumps, the whole driver's side rear cab was not being supported and that made the door rattle.
Since that spot was rusted on both trucks, I am thinking that might be a common problem, though it hasn't happened on my 89 yet. A good way to test it is to get a crowbar and try to pry up the cab near the rear cab mounts.
