Definitely sounds like something is binding up. I haven't done one in the truck yet, but in my '86 Cutlass I've replaced one motor and will probably do the other soon along with both in the truck. They are actually very easy to do and cheap. At the very least, I would take the door panels off and watch as the window goes down. See where it sticks and if there is something in the tracks. It could be that the track system is loose and as the weight of the window moves, the gears get out of alignment. Just one important note, make sure the window is down all the way before replacing the motor. The motor is what locks the window in place, and if you remove it with the window up, it will come crashing down and can be very dangerous to your fingers, hands, or anything else in the way.
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