What is a shift actuator?

On modern top load washers there is no gearbox deciding whether the machine agitates or spins, a small synchronous motor called the shift actuator moves a cam ring to engage one mode or the other. It is the single most common failure on the Whirlpool VMW platform and its GE equivalent, and it produces a machine that fills and drains perfectly but never spins or never agitates. It is an inexpensive part held on by a couple of screws and one plug, which makes it one of the better value repairs in the laundry room.