Here is what I was told about PTU's an why some fail with sludge and some look perfect @ 60K
Basically when they come off the assembly line, if they are manufactured correctly and the tolerances are in line you will get a long life without a fluid change.
Apparently QC isn't all that hot and that isn't happening....tolerances are off, more friction and lack of movement cooks the fluid and ruins the PTU.
Most rational minded folks would agree you really can't over maintain something like a PTU. The problem is it has been alleged by certain unscrupulous service advisers that Ford will void your warranty over it which is absurd IMHO and puts folks under warranty in a bind. Don't maintain it under warranty for fear of cancelled warranty on that part or listen to Ford and risk a failure when it goes out of warranty. Quite the conundrum. I say allege because it's not something Mrs FoMoCoSHO has ever encountered and you guys would be surprised at some of the modded vehicles they are able to get covered with Ford fully knowing what has been done to the vehicles. Ford wants to sell cars and pi$$ing off your loyal customers isn't the way to make that happen. And she has surely NEVER had a warranty denied for over maintaining a vehicle.
The first thing to do is try to find a dealership that will service your car how you want it without threats. Bottom line IMHO is they are lazy and don't want to deal with it. I'd suspect the dealerships that are willing to do what you ask will get it covered if there happened to be a failure. They know these things fail for no good reason and a good dealership will always fight for their customer.
My suggestion is service your vehicle to the level you feel appropriate. If you have a failure under warranty they will not cover make them put it in writing WHY they wouldn't warranty it.
If the worst were to happen....
Call Ford first and hammer them on social media with pics and links to the PTU failures found all over the internet. Be persistent. Be that festering wart on their a$$ that they just want to go away.
If that tactic fails take it to 3rd party neutral warranty arbitration where their lawyers are moot. Give every member a copy of Magnusson Moss and present your case. Remember the burden of proof is on Ford to PROVE that over maintaining your vehicle caused the failure. And as long as you have the correct volume and type of fluid? Good luck with that. Most likely that will never happen and once you let your intentions be known, the PTU will be replaced.
Remember, there is plenty of evidence on the internet regarding fluid condition and premature failures. During arbitration you will get your chance present your evidence and to ask questions like, what specifically would cause newer fluid of the correct specification and filled to the proper level to be detrimental to the life of the PTU??? Seriously, GTFO, it just sounds ridiculous when you say it.
I seriously doubt this situation would ever get to that level. The first line of defense is finding a good dealership which I know is sometimes much easier said than done. Do you think Ford wants to risk your next $50k purchase over an $800 PTU that is marked up 40-60% to start with?