By hacksawing I think he meant hacksaw through the old gearknob not the stick itself!!
That also depends in the gear boot stretches to fit the new gear knob or not. If not, you'll need to cut the metal stick like I did. It makes the shift slightly shorter and allow the boot to wrap around the gear knob properly.
"I changed the knob on my 156
The steel shaft has 2 "fins" 180 dgr oppossed that holds the original knob
Just take a heavy adjustable wrench, "grab" the old knob just above the
steel shaft and turn the wrench with HIGH force; the hard plastic center
piece will break and allows you to remove the knob. This sounds a bit
uncraftsmanlike, but thats the only way!
The new knob most likely will have "an Allen screw" to secure it to the
Afraid that doesn't work for the JTD, it has a reverse gear lockout jobby and a splined shaft, often glues on too! Hacksaw or many LIGHT taps with a hammer and block of wood are the only way to go. I chose the latter to keep the knob in one piece.