You don't say what year 240 you have--I know the early cars have a "tamper lock" on the plastic cap that screws onto the speedo drive. You may need to remove the front seat if you can't squeeze yourself under the dash to take a look. The "lock" consists of a plastic ring around the perimeter of the plastic cap. If it's there you need to take a flat screwdriver and slip it between the ring and the cap and then break it off. Now you casn grab the cap with your fingers or pliers and turn it--top side towards the passenger side to unlatch-about a 1/4 turn--now wiggle the cable conduit and it should pull free of the speedo.-- Dave