When my Chevy van power window was not closing tight and slowing on the lift, I thought I needed a new motor. At the entrance to the junk yard I go to a worker refitted the rubber around the track with a used replacement and it works terrific now. Carefully observe the track. Sometimes a short rubber section is slightly tweaked creating extra resistance. Straighten and loosen everything especially if your window creeps very slowly at the end of its travel.