On my 1977 I pulled the drivers door apart and replaced the regulator and motor. I also pulled all of the track and cleaned all of the old grease out of the rails and greased it up good with lithium grease. The window goes up and down like a guillotine now. It's faster going up than going down but it goes both directions very smoothly and very fast. The problem is that sometimes when it goes up, if I don't let go of the button before it gets to the top, the window will get jammed. The door still opens and closes fine but the window won't go down until I loosen the bolts that hold the motor to the regulator. Once it moves I can tighten back up and all is well again until the next time it hits too hard. It doesn't do it every time even if I don't let go of the button but every once in a while it will jam. The windows is jammed whether the door is open or closed so it's not jammed against the weather stripping, it's jammed against the stop blocks in the window tracks. I have both stop blocks in place so I don't think the window is going crooked, in fact, even when it is jammed it looks really good against the weatherstripping on all sides. I did the same clean job on the passenger window and replaced it's motor but I did not put in a new regulator. The window goes up very nicely but not as fast as the drivers door and it never jams.

 

I HAVE A 77 also and had similar issues. Check your bumpers they may be to tight against the window. Is the lower horizontal track centered. To high or to low will affect the window travel. Also check the stops at the top of the vertical tracks. Good luck.

 

did you have a close look for worn or damaged teeth on the motor (drive cog) or more likely , regulator? If their worn at the contact point , where the glass is up, they can bind together.

Having to loosen the contact between the teeth and cog is a give away to where the problem is located

 

Hopefully you took the time to make sure you indexed the motor on the regulator due to the three machined sleeves that are on the area of the motor where it has to engage into the regulator. If these sleeves are not IN the mount areas of the regulator the motor can now change its position and bind up

When the motor can move on the regulator itself..the metal plate with the bushing in it can also move.,.,.thus allowing the teeth of the gear on the motor and regulator to bind up.

Reason I say this is I have seen many new motors NOT have the correct machining on the ends of the three mount points of the motor...thus making it a piece of junk....even though it may work electrically....it can rotate and slide.

DUB