The other day a couple brought to the shop a 2010 F150 equipped with the 6R80. They just happened to have left the nearest dealer who painstakingly tried to fix it, but having failed, these customers were at our door. Their issue was their truck would not shift out of 3rd gear. The previous dealer tried to install a new valve body and a megatronix assembly to no avail. Not only did it not fix the problem, but they also went ahead and did a warranty repair claim to Ford for the valve body.
I drive the truck and sure enough, it starts out in third gear and never leaves it. I hook up IDS and see the code for incorrect gear ratio for fourth gear. I clear the codes and retest drive. The truck starts in first, changes to second, then third, and attempts to go into 4th gear 3 times with no luck and then defaults to third gear. I dig through some workshop manuals and discover the only clutches that engage in 4th, 5th, and 6th is the overdrive clutch. I then remove the valve body assembly, and do a air pressure check on the hydraulic port for the overdrive clutch and hear a loud hissing sound. Diagnosis is complete.
The transmission is removed from the vehicle and disassembled to find a broken piston cup. Replace the effected parts under warranty, reassemble, an test drive. All is good for everyone except the original dealer that did an improper repair - I am sure they will experience a chargeback.