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What is the model number of your unit, please?
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the ratcheting sound is caused by a worn Plastic helix, transmission drive pulley, you need to replace it. this is under ten dollars and you can order it @ http://www.repairclinic.com/PartDetail/Gear/40047402/889619 they come with instructions. its fairly easy to replace tip the machine back and the main transmission pulley has a C clip remove that and then the pulley and the helix gear is above that . hope this helps. thanks ,Bryan