Raydar: exactly right, but for a "pop" just a few inches from bottom on the way up. The "Christmas tree" off-white plastic push-in fastener on the inside door panel bottom rear must be cut off to about half length. For a while I had two "pops", the lower one due to the push-in fasteners for the inner panel being all the same full length. Some other group members educated me on that last fall.
Shemdogg, back to the upper "pop":
It's fixed! Background - the passenger door is not original to my 88GT. For example, someone cut little rectangle access holes in the top of the door frame so the felt pads could be changed without taking out the glass. Whomever they were, they did a good job. Complete with hard cover for each hole and two small Phillips head screws to attach each cover. I used the holes to install new felt pads last fall.
I noticed about an hour ago the adjustment for the vertical channel [see below excerpt from a window adjustment post]
"Adjusts the in and out of the window against the frame and is adjusted in conjunction with the BLUE circles. If you get the window to tight against the seal then it will be hard to roll the window up. to loose and you will get leaks and wind noise.
I think there is another in /out in the "nose channel" in the front but I'm not sure because I have never had to adjust it."
Back to me, John T: the toward the inside and away from the inside adjustment for the channel was on full away from. I loosened the two 10mm hex head screws and brought the top of the channel about one eighth of an inch back toward the inside. While the screws were sill a little loose tried raising the window. Smooth and no pop. Took it back down half way. Tried up again and it popped. Took a look at the adjustment. The loose screws had allowed the adjustment to snap back to full away from. I put it back to 1/8 inch in from full away from and tightened the screws. Up and down several times with no pops. Closed and opened the door. Glass fits rubber molding around door. Closed door and lowered and raised window. No problem.
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John W. Tilford
[This message has been edited by John W. Tilford (edited 05-11-2023).]