Hey, thanks for all of your help. A few updates...i've reflashed the PCM which didnt help. Turns out the Program that was originally setup in the pcm was for a 3500 express van with a 6.0/4L80E. BUT, the tuner changed the segments and such for a 5.3/4L60E. And there was one of the tables that he forgot to switch, so in his words the transmission was "shifting like a 60, but searching for faults like an 80". so, he sent me a new PCM with the correct parameters. Since going back and forth with different PCM's and different tunes/programs, I discovered that the tranny was actually screwed up (burned up clutch packs and the like). So I had the tranny rebuilt into a megabeast. Corvette servo's, hummer planetary gears, shift kit, Zpack clutches, and other stuff. Then the truck started running F'd up. Turns out, the top clip on the 2" rubber hose between the fuel pump and the pickup tube had came undone (silly me for using the plastic clip supplied with the pump), and that was allowing fuel to bypass the pickup tube and fall back into the tank. Which burned up the fuel pump. I only had 21 PSI at the fuel rail with the engine running. as soon as you keyed off, the pressure dropped to zero. So, i did the pump yesterday. Motors back running healthy. And low and behold (keep in mind, rebuilt transmission, and new pcm with corrected parameters), BAM right there as i'm moving onto the off ramp going home, it kicks out of gear again. Same problem. Same thing with turning it off, and back on and the problem goes away. So, I spent a couple hours farting around on google, and other LS related forums, and found a thread where a guy with a camaro was having the same issue while he was cruising or in moderate traffic at part throttle. Word for Word exactly the same symptoms i was having. He was able to figure out that there's misfires that occur that dont actually throw a diagnostic code. and these misfires are causing the converter to unlock while at cruising speeds. Coincidentally, he's also using the E3 Diamond fire spark plugs. This guy ditched the E3 plugs, and went with the conventional recommended stock plugs, and went into HPtuners, and was able to Max out the misfire tables, and the guy hasnt had any problems since. SOOOOO, after 6 months, and somewhere in the neighborhood of $3500-$4000....I'm pretty sure i've finally found the fix for this. So, this weekend I will be chunking those E3 plugs, and picking up some NGK's, or something similar. Maybe just that will fix it. otherwise i need to find a good reputable tuner down here, since the speed shop that did my last tune moved like 2 hours north, and the other guy that did my pcm lives in Michigan. I will keep this thread updated, and hopefully the next guy with this problem will find this, before he spends a small fortune like i did.
