Clacking sound

I have an Amana washing machine. Yesterday during the spin cycle it started making a very loud noise, like a very fast clacking. I open the front panel. If I spin the belt the way it is turning then it looks like it must make that clacking from the way the gear is made on the bottom of the tub. If I turn the belt the other way it spins the tub. It almost looks like the motor is now spining the incorrect direction. But I don’t understand why that gear at the bottom of the tub would be designed to slip the other direction