C4 power windows have gone through a few engineering changes from the agonizingly slow '84-'86 ribbon-lift windows to the later scissor-lift windows. The design stayed roughly the same except for the actual lifting device until 1994, when a front window guide was added to lessen window rattle and slop when the window was in any position. Previously, unless the window was fully open or closed at the limit stops, rattles occurred when you closed the door or were riding down the road. Nothing is foolproof, and the window-guide design proved to have a weakness-eventually the guide breaks, and the window has no upper limit stop at the front. The guide also doubles as the upper window limit travel stop. When the plastic-guide/upper-limit stop breaks, the window can become extremely out of position and, in some cases, glass breakage occurs. Corvette coupes get a double whammy as the glass can break, and the paint at the rear pillar gets scraped.
Nobody looks at the window for positioning before they close their door, unless they've noticed the window doesn't look quite right. If all of a sudden the window is too high at the front, most likely the stop is broken.
The task of fixing these issues is not too difficult, You can plan on spending a couple of hours removing the door panel and fighting the thread locking adhesive retaining the upper window stop to the glass. On the up side, the door panel can get a thorough cleaning while everything is apart. Our particular guide/upper-limit stop replacement Corvette had this issue for a while, but we recognized the problem and kept the window down a bit to compensate for the annoying problem. But enough enough's as they say, and it was time to rectify the situation.
Things You'll Need