IF you have a newer 2850s Valve, you'll need to re-use the "link" from your Main Piston to the Drive Cam, and not the one that comes with the new power head.
Does not include Valve Body or Brine Piston Assembly.
Cover can be Selected when placing order ( Cover - Optional drop down selection ) for an additional amount.
Old Style covers with two screws on the sides will not work with this power head.No instructions, but...........
Installation is pretty simple.
Unplug, and turn off water ( or by pass valve ),
You remove the 2 bolts that secure the plate to the valve body,
You remove the PIN from the Main Piston shaft....
You unscrew the front of the Brine Valve Piston assembly ( if water softener valve.. backwash only don't have a Brine Valve ).
And you can then pull the power head off and away from the valve body.
Installing is the reverse,
And setting of the timer assembly is explained in the manuals,
but you really would just set Time of Day and compare the program wheel pins on your old Timer Assembly to the new one, and move or add PINS if necessary.
see Pages 4 and 5,