So, the motor in your washer runs and you’ve laid eyeballs on the belt to confirm that it’s not broken, but still no spin. Trying to Help, a Sublime Master of Appliantology in the Samurai Appliance Repair Forum, explains how to tell whether the problem is the transmission (that’s bad), the thrust bearing and pulley assembly (that’s not as bad), or something else:
Pop the top of the unit up like you were going to take the front panel off and start the machine in the spin cycle. With the unit running, and sounding like it is spinning, reach in and see if you can turn the inner tub easily by hand, almost like a roulette wheel. If you can turn it freely by hand, then your brake has released. This would mean your belt, brake, motor pivot and trust bearing kit are all fine and your transmission is slap tore up (defective). IF you can not turn the tub freely at this point, then your brake is still holding. At that point, make sure your motor is pivoting back and forth freely and inspect your thrust bearing and pulley assembly as the Samurai suggested, and check for items stuck between the tubs such as a sock or wash cloth.