To get the one off of my B14 SE-R....
I had to remove the entire shifter, wrapped the knob in a towel, drove over the knob with a car, and parked the tire right on top of the knob. Then I took a bar and put it through the bolt hole on the bottom of the shifter, and used about 5 feet of leverage to turn it, and it finally cracked loose. I would recommend that for 240SX knobs as well, if you can't get them off, however...since the 240SX is RWD, it does not have the same bolt hole at the bottom of the shifter.
And on my car, it *was* epoxied in there. You could see where I broke all the glue on the threads, taking it out. But, the knob survived, and I continued to use it on my C's shifter
On my B15 SE-R....the knob came loose after a week of driving. I had to tighten it down a few more twists
