How to remove the washer cycle selection/start-stop knob on a Whilpool Heavy Duty Thin Twin stacked washer dryer

I believe the selector knob on a Whirpool just has to be turned counter-clockwise with the selector pushed in. It will spin off the shaft and then the outer indicator dial will pull off. The shaft also has a keyed slot that will only allow the dial to be removed and installed one way, so there should be no question as to how it goes back on.

Was there a reason as to why you are removing the washer selector knob? If this is a simple matter of replacing a broken water temperature selector, you shouldn't have to remove any of the control knobs to gain access to the selector. The entire front panel comes off by removing the screws holding it in place. That way you can access the broken selector from behind the front panel much easier. Just remove the panel right above the washer top (under the dryer) and it should expose the front panel mounting screws. Remove these screws and the front panel comes off. Just make sure the unit is unplugged before you begin. I hope this helps you. Let me know if you need further assistance.