The 66rfe in my 2014 Hemi blew @ 38K miles under totally minimal circumstances. I was sitting in stop/go traffic and when rolling along at about 5mph I pushed the accelerator to speed up - the RPMs went up and I pretty much stayed still. I limped it a mile or so to an exit and got towed to the dealer from there. Word was the valve body exploded and wiped out all the internal parts. I got new steels and some other stuff - I honestly don't know much about the inner-workings.
My usage of the truck is completely within specs. I am 1000% stock - no chips, over-sized tires, lifts or any mods at all. I tow a 5th wheel very rarely - probably less than 1000 miles total and not within weeks of when the failure occurred. I'm a boring middle aged guy that uses my truck as a commuter 99% of the time.
So, the tranny gets rebuilt and basically drives like crap. I have a TERRIBLE shudder when doing a 2-1 shift under a light load - like coasting into a speed hump and then accelerating. When hammering it (which I rarely do) it responds fine. It's just when under med/light throttle the tranny seems to get lost. Next, going the other direction using the engine braking (with the manual up/down button on the shift lever) when it selects 1st gear as it shifts from 3-1 there is such a violent "crash" that my suction cup phone holder falls from the window. The rear wheels actually skid it's so bad. Honestly, I just avoid this but there is obviously something wrong.
MY dealer has been completely useless in helping me (other than rebuilding the broken POS I suppose). They make excuses and deny anything is wrong.
I'm basically stuck in limbo with my lifetime warranty (thankfully) waiting for the thing to just take another dump and maybe I'll get a better fix. If I had more time I'd probably be hassling my dealer more to do something. It's just discouraging. The last time I was in I sat in the waiting room for 2+ hours and the service writer couldn't even communicate to the tech what my complaint was. By the time I spoke up and asked the tech to take a drive with me he refused saying he was too busy.
Of course, all of this is out of the ordinary I know. A failure like I experienced is statistically rare.
Aside from that problem I of course think the tranny has terrible ratios (especially for towing heavy loads) and completely ridiculous shift points - the same things that get complained about daily on this forum.
I love a lot of things about my Ram but would be hard pressed to EVER drop 40K on another one. I'm basically just playing the waiting game hoping the thing takes another crap so maybe it will get fixed for real. Taking a crap of course when I'm not in the middle of nowhere with my 5th wheel and family along for the ride.