There isn't any unbalance sensor in this washer nor any way for it to slow the spin speed. Most likely, you need to replace the clutch but other possibilties are sticking brakes, worn drive block or gearcase issues.

Whirlpool 285785 Clutch Assembly - AppliancePartsPros.com

Eric

The reason for the slowdown is for the reasons I gave you, not due to any electrical/electronic control of the washer.

Eric

I can't say for sure from here. It is the most common problem causing a slow spin but several other things can cause this. You can remove the agitator and check the condition of the top of the drive block to give you a good idea of whether it is ok or not. After removing the agitator, if your washer has them, remove the clip and plastic washer from the agitator shaft. The slots in the drive block should be intact as should the tabs on the spin tube and they should be fully engaged. You must remove the agitator and gearcase to check the clutch. It should not be too easy to spin the clutch band within the clutch housing. If there is any oil in the clutch housing, the cover seal or spin pinion gear seal in the gearcase may be leaking. There should be at least .10" of clutch lining between the surface of the pads and the rivets holding them on. After removing the gearcase, grab the brake cam driver and rotate it CCW. This should release the brakes and allow free rotation of the basket. Push on the basket drive while doing this to make sure it is fully up into the brake housing before reinstalling the gearcase. Do not buy your clutch or any other parts from amazon or e bay. Only buy genuine Whirlpool FSP parts. You would only get a few loads out of the $8 clutches sold there.

Eric