Picked up a 78 300d, runs good but owner said trans was bad. Car shifts fine except when you go past three quarter throttle. Upon inspection i discovered the bowden rod was not attached to the trans, and the lever that goes into the trans was missing. Is there any reason why someone would remove it.

Ignorance? They may not have known its function.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
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I would hook it back up and see what happens.