The low speeds on my J-hesd haven't worked in 25 years. I've never really minded because I really didn't have anything to run slowly. However, i feel like it's time to get to the bottom of it. I feel like I'm following the instructions for shifting from high to low, but all i get are ugly grinding noises when I turn it on in low. I remember the machinist telling me that something was wrong with it 25 years ago. Are there any common failures of this sort with this machine?