When in spin the agitator will slowly spin but with no power to it so that is normal. With that happening and the clutch spinning then the gear case is working good.
The only things left is the basket drive (sits on top of the clutch) and the spin basket.
Make sure nothing is between the tub and spin basket. Its hard to see because the plastic is not very clear. Use a bright flashlight on the tub and its easier to see inside.

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