Auto gear knob

There is a small grub screw on the front(nearest the ashtray) of the knob. I assume removing this allows the knob to be lifted off.
 
Remove the Allen screw on the shaft. Lift the knob and twist to break the wires to the overdrive button. This I believe is the only way. Make sure overdrive is in the setting you want then just tape the wires off or you can splice in a button to the side of the center console for it and use an aftermarket shift knob