I found the procedure in the 700/900 FAQ. The procedure for your 240 should match the procedure for the 740, since the shift knobs were almost identical.

Here's the link:

http://www.brickboard.com/FAQ/700-900/TransmissionAuto.htm#RemovingShifterKnob

One suggestion I would add: Before removing, you might want to place a plastic sandwich bag over the knob and secure it with a rubber band around the bottom, as there is a fairly strong spring in the button assembly that will cause the entire works to fly all over the car if not secured. You don't want to be searching all day for that stuff.

Best of luck.

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Guid ('92 745 257k, '91 940 SE 278k,)