You need no special tools, Whirlpool made it so!! Go to
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When you get to the tranny, just pound in the new coupler and turn clockwise.
If is very hard to turn with one hand, you have other problems like dragging brake shoes or something caught in the tub.
I always check the motor current in spin when done, should be around 9 amps.
You can click on your model # above to get your coupler.