Control of the mode shifter comes from the motor inverter circuit. First the motor senses the load and engages the drive, after the tub fills with water. When the washer starts agitating, the inverter sends power to the mode shifter coil for about 18 seconds. The power is 135 volts of direct current, which lifts the mode shifter cam and disengages the drive pulley -- now only the agitator shaft will rotate.
During the 18 seconds, the motor also rotates in short clockwise and counterclockwise movements to make sure the mode shifter cam has come off the drive pulley. This is the mode shifter agitate program, and the metal-on-metal sounds of the cam and drive pulley disengaging are normal.
The washer runs the mode shifter agitate program at several times: when the agitation starts, when lost power comes back on and when the user restarts the top loader from "pause." After 18 seconds of the program, and its clicking and clacking, agitation starts. During the agitation, the inverter motor keeps 30 volts of direct current going to the mode shifter coil. This is enough power to hold the mode shifter cam away from the drive pulley during agitation.
Repair and Checking
If the shifter cannot lift the cam up and away from the drive pulley, the whole tub will move during the wash, according to the Appliance-Repair-It.com website. This means clanking noises will continue during the wash cycle. You can check this by removing the front panel of the top loader -- by depressing two clips between the top and front. If you see the inner tub moving during the wash cycle, the shifter coil could be faulty, which you can check with an ohmmeter and decide whether to replace the coil or the motor.