It is the 2-4 servo piston. To repair this is quite simple.
Buy a jack with small tip. 20 dollars at Auto Zone. Purchase new snap ring from Ford for about 4 dollars. Purchase new cap from Ford for about 10 dollars.
Place jack under cap and jack into place into housing. be sure to coat with atx fluid. Continuing jacking until cap clears snap ring land. Place snap ring into place. Total Cost about 34 dollars. Will take you no more than 15 minutes.
Bob
