It's your drawbar or the top of the spindle.
After years of tightening the drawbar it has left
the top of the spindle with a burr on it or the
drawbar is rubbing, maybe it is bent. Take your
drawbar out and look at it. Maybe buy a new one.
If the drawbar doesn't work then the top of the
spindle has a burr where multiple tightenings the
drawbar has mushroomed the spindle and when
the spindle runs through the splined gear hub
it rubs. Then take the spindle out and clean up
top of the spindle with a Dremel tool and a grinder.