1969 280se manual trans gear shift knob
 

The spherical gear shift knob on my manual floor shift lever does not want to come off. I don't know the internal construction but the knob turns counter clockwise very sluggishly and does not come off. It feels like the plastic ball is just turning around possibly a metal bushing that is threaded, screwed and frozen to the shift lever. I could not find any set screw access holes on the plastic knob Does anyone have experience in removing W108 gear shift knobs? Thank you from Menlo Park, California, USA.