I totally agree with your list of possibilites and are definitely worth checkn out but if you lay a wrench on that Valve train that is exactly what I was referring to as a waranty escape route.
I had delayed engagement in my trans, getting worse and worse. Took it in they said they could duplicate the prob, so I changed the fluid and filters, this is at like 43k miles. I used redline full synthetic, super careful, and the trans seemed to improve but the problem was intermittent, a couple months later, kachunk, never threw a code through all of it. And suddenly I need a new trans and they blamed me for the failure because I changed the fluid.
I didn't realize the significances of delayed engagement or my attorney would have been the next voice they heard instead of me paying $5500 for new trans.
It was reported, documented, given to them for analysis and repair, they still had the audacity to blame me, and I let em get away with it. Power train warranty and lifetime warranty, trans is days away from failure and I touched it and was straight up about it, soooo they let me buy the new one.
I don't promote not being straight, but if I had to do it again, i would not confess that I tried to do something when they wouldn't.
Anyway, just so you know, Be careful who you tell what you been touch n, but no matter if it's me I'm probably gonna touch it any way. The longer it goes thrashing about with something loose, the higher number of parts will be affected. If they'd have fixed your lifters immediately, you would not have a possible bent rods or worn cam lobe but they don't be seem to be focused on our long term loyalty. Fkrs!
Good luck with it all
Changing fluid, if done correctly, never had anything to do with trans failure. You must be wealthy to have $5500.00 to plop down on a trans!
All you and your attorney needed was a professional trans tech to testify to that fact. Delayed engagement is a huge red flag, btw.
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