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remove the Hot battery lead while the motor is running.


NO NO NO NO! This sends a huge voltage spike to the alternator, and will probably fry the voltage regulator, at best shorten it's life significantly.

Pull the solenoid wire from the starter with the engine running and the starter should disengage. The sound may be the overrunning clutch in the starter pinion. crawling underneath with it running and using a piece of vac hose in your ear to localize the sound should make it easy to find.

Not responsible for advice not taken...