2010 and up Ford Vehicles equipped with the 6F35 transaxle may suddenly exhibit a concern of a harsh application in reverse and or a harsh up-shift into third gear. This may also be accompanied with what feels like a slight bind up during the 2-3 shift transition.
The cause may be a check ball problem in the valve body. Sam Daniels of Powers Transmissions in Kentucky sent in pictures showing how the Drive 2 check ball in the valve body (figure 1) has damaged the check ball seat in the spacer plate (figure 2). This causes a poor seal of the check ball allowing the exhaust backfill circuit to be charged with pressure affecting the shift. There have been incidences of the check ball blowing completely through the plate. Damage to the Low/Reverse Clutch may also occur as a result of uncontrolled Drive 2 oil.
At one time, the only way this could be repaired is with the purchase of a new valve body. The part number was BL8Z-7A100-A which has been changed to CV6Z-7A110B. This valve body is $109.22 with a core deposit of $275. And this may be needed as the solenoid regulator valve in this valve body is notorious for wearing out the bore. If the bore is not worn, an updated spacer plate can be purchased separately for only $5.67, part number DV6Z-7Z490-B.