5600 Timer Retaining Pin
Fleck 5600 Timer Motor Retaining Pin
If you have replaced the main piston ( # 60102-00 for water softeners ) and the brine valve piston assembly ( # 60032 ), and your "freely" turning valve still gets stuck, then it is time to take a close look at the Timer Gear Retaining Pin. The pin does not show in most Manuals.
It is this pin which keeps the motor gear engaged on the Idler Gear ( part # 13017 ). Check the condition of this pin and the Idler Gear.