I've had a few issues pop up lately - going to try to explain in chronological order. Things to know: The truck runs amazingly well (smooth and powerful), trans shifts great, no real issues. 230k on the odometer. 4R75e, 4wd, towing package. Plugs 50k ago, Trans-pan fluid and filter 50k ago. Basically, about 2 or 3 weeks ago I started noticing a small "rumble strip" shudder around 40mph (low rpm, low throttle, high load - just bordering on the 4-to-3 downshift). It's easy enough to avoid, just don't linger in that "keeping it from downshifting throttle position" as it is gone as soon as the trans shifts. This really only happened when loaded down with the band and our gear (I'm a touring country artist) or when pulling a trailer, but it happens every now and then when it's just me and I'm going up a hill or something. So of course I check mode 06 and find #4 has about 30 misfires registered. I pull the coil, clean the terminal and spring (corrosion), apply dielectric and reinstall. It's been a week and a decent amount of driving - no more mode 06 misfires on any cylinder (this never triggered a MIL at all). Thought this fixed the shudder until I had a truck with some cargo weight and it was back. Next tried shudder fixx just to see if it'd calm the shudder down, as I was still wondering if it was the TC/trans or if it was the COPS/Plugs (again, plugs are 50k old... all but one COP are unknown mileage - up to 230k in theory). Shudder fix didn't seem to affect it. Still, no MIL or Mode 06 so I'm not leaning toward misfire... but I don't know much about mode 06 and how accurately it catches EVERY misfire...? Ok, today I was backing out of a parking spot. When I braked to stop and shift into D the truck stalled. Nothing violent - in fact, I had to look at the tach to know what happened (to be fair, the A/C fans were up a couple notches so I couldn't hear the engine). Weird. Restart and for a few minutes it's kind of weird but seems to go back to normal. Now, I'm taking off from lights and thinking the acceleration is off. Like I'm lacking a bit of power, even though the engine is running like a top... so maybe TC slipping. Maybe in my head, maybe not.... hard to say. One other thing to note: about a week ago I had two single instances of a P2135 (throttle a/b mismatch), accompanied by "engine failsafe mode" that would go away after cycling the key. I've driven 6-7 hours since (trying to trigger it so i could better diagnose) and it hasn't returned. Possibly a fluke due to a shot battery (since replaced) and horribly corroded terminals. As of now I feel it is unrelated to the trans issues.