From my personal experience, both brand new Ram 1500's of mine (19' and now my 23') were 1-liter+ low on trans fluid right from the factory. The transmission just wasn't feeling 100% to me, and I'm pretty good at knowing my vehicles and how they run. I had the dealership check them and they filled them up properly as per the "Green Sheet", and updated all the computer systems as well. Then I took my rig out and drove it like I stole it to ensure no granny mode was present, and all was good
I would take your truck in while it's still under factory warranty and ensure that they check for any transmission and system updates, AND physically check the current fluid level as well (also ensure they are checking the fluid level properly with the "transmission" being level and at the correct temp).
The trans cooler bypass won't void your warranty as they'll never see it (technically it does though).
The new larger aluminum trans pan is obvious and if they aren't a "cool" dealership, they'd surely give you nothing but grief (my dealership is awesome and wouldn't balk one iota for me, and they haven't at all for anything I've done, including a custom mandrel bent y-pipe
)
As for extended warranty... meh, I have personally never purchased one.
My 3yr/60,000km bumper to bumper and my 5yr/100,000km powertrain warranty is all I need.
However, I do have an exceptional dealership to work with, and mileage really doesn't concern me because it really doesn't concern them
). - Tough call to make for you, Brother.
If your truck has been reliable to date, then I'd not waste a dime.
Do your transmission/transfer case/differentials/coolant/brake fluid/spark plugs/PCV valve/throttle body & intake services (including tightening the bolts as they are known to come loose and cause drivability issues) - brake caliper services - replace the idler & tensioner pulleys and serpentine belt, etc.... and have a great ownership experience.
