Ford Think High Pitch Sound

Hello everyone. For those who aren’t aware I purchaesd a 120v ford think about 2 years ago. There is a total of 10 batteries and the motor was said to be wounded up for speed and torque. I believe its the stock motor as well. I have always heard a high pitch sound when I intially depress the gas pedal. The same sounds occurs when i let go of the gas pedal. It reminds me of a fast speed roller coaster at take off. Well since I have never heard a stock Think, I have no idea of what they normally sound like. I have attached a video in hopes someone can diagnose the sound. Thanks in advanced. With CA gas prices I find myself driving the cart even more so i just want to make sure its up to par.