I have a Maytag Performa washing machine - about 5 years old. It makes a grinding noise when washing. Spin cycle is still quiet. Any suggestions about what to check?

You'll want to pull the pump and motor, it is probably a broken coupler.

Instructions & Reference (http://www.sannerud.com/house/kenwash.html)

Note: the link above is to Kenmore brand, however it will give you a good idea on your model.