Removing shift knob
 

I have an 83 911 SC and want to install a leather boot and knob assembly on my shifter. The problem is, I can't get the old knob off. I tried the open end wrench under the base of the knob and tapping firmly with a hammer routine but it won't break loose. Any suggestions ?
Thanks in advance.

get a good grip, pull hard and twist at the same time. if all efforts fail, break it with channel locks.