Do your AD truck windows vibrate open a 1/2" or so from the fully up position? Mine did and I've spent the past day or so figuring out how window regulators really work. The regulator is a very very clever thing that, when working properly, only allows movement from the crank side and prevents movement downward from the window side.
It all happens behind the riveted cover over top of the winding gears. There's a small coil spring in there that only allows motion from the crank side. If the spring is broken or really dirty, then the weight of the window can force movement from the window side as well as the crank side. That allows the window to "sag down" or refuse to stay fully closed.
The solution is to drill out the rivets, remove the domed shape cover and check the spring. It must have two small tangs on it to work properly. If the tangs are broken, then you'll either need a new regulator or go to the local boneyard and salvage a regulator and remove the small coil spring. If the coil spring is not broken, then pull it out of the domed cover and clean everything well in solvent, oil it and re-install it. Getting the assembly back on with the VERY strong spring that holds up the window is a bit tricky. Pull it back with pliers or vise grips and then slide the gear assembly into the regulator. Use 8-32 machine screws to replace the drilled out rivets.
Hope this helps all those who don't want to buy new regulators. And fixing stuff is cool.
PS.... to remove the regulator assy:
1. remove screws attaching reg. rail to the window glass
2. hold the glass in the fully up position with some wire or heavy cord
3. remove the regulator screws and pull the regulator assy out thru the access hole in the bottom of the door.
4. inspect/replace/clean the reg. assy as described above
5. put the reg assy back in the door thru the access hole and attach it to the door.
6. re-attach the window.
should take a couple of hours
