I have a 3.9:1 (non-L.S.D.) differential removed from a 1976. When I turn the drive shaft flange by hand everything rotates smoothly. When I turn the drive flanges in opposite directions, they feel notchy. The end cover is off and I don't see any worn teeth or metal particles. It seems that as the spider gears mesh to tight and they hang up a little as the top of each tooth passes. Should there be any notchiness as you turn the drive flanges or should they turn smoothly