Funny, mine does the same on my 68' except it "skips" the last bit,not allowing it to wind up the last inch or so and i have to pull it up by hand if need it up all the way.Personally i think my regulator is toast and was going to replace it.
David
http://FirstGenFirebird.org/show/closeup.mv?CarID=571 If i don't get this car back on the road soon i'm gonna go postal! On a quest for FGF knowledge 1968 Pontiac Firebird Convertible 1969 Oldsmobile Cutlass "S" Convertible *Sold*