It's only the shift knob caps made for the '75-'80 240s with stick shifts that tend to really crack. They used an actual switch for the OD instead of a push button. The design is much weaker however:

Here's a couple of pictures of my '80 with the old design:


Easier to see the cap seperation here... although that duct tape is no longer there:




Here's a picture of the later design courtasy of Nickvjr:



As you can see, the cap does not roll over the edge of the knob like the earlier design does. That's where the flaw was on the older models.
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If you listen to the radio in Portland, OR, you may know me as 'Portland's Favorite Soul Brother!'