I found on my 85 chevy sprint that the felt stuff was put in the track incorrectly.. There was a part of the felt that had a notch cut in it that was meant to be in the corner of the door. It was put in the door about i assume it was there, [it may have worked its way there] ..
jaguar,vettes&sprints pointed this out to me at the WestCoast Meet... He took out the felt stuff, re-inserted in the correct way and area.... No more trouble with the hard cranking.
This may be what you are having trouble with, also...And maybe not........
