A stretched cable is one that has become longer in length than it's original length.
You could try pulling back on the clutch pedal and see if you can ratchet the quadrant. This will adjust the clutch...worth a try anyway.
I would start with the cable and then the quadrant. If that is not the problem you're going to have to pull the tranny and inspect the clutch.
It does sound like a more serious problem than the cable or quadrant though. How many miles on this clutch?
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fordgasm
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