the washer will not spin. the belt is in place, and all the pullies will spin, but the tub will not spin. the tub will move very little at times during the spin cycle. the belt has some slack, but could it be too loose?
This is the usual fix for your problem. It contains instructions.
If this is not the problem you may have a brake or transmission problem.
Here is a service manual for your model.
http://www.servicematters.com/maytag_library/docs/16023083.pdf