Had a productive conversation with the transmission guy I'm going to use to repair my Yukon. He called around and found a GM reman 6L80 with heavy-duty upgrades (valve body, solenoids, I/O shafts, etc.) in stock at the local GM dealer. He said they typically take a month to get, but we got lucky. Going to add a pan with a drain plug. Also changing transfer case and diff fluids, new radiator (cooler undoubtedly is full of debris), and for good measure going to add an auxiliary cooler. I'll lose whatever TCM tune BB did. But this guy has a dyno, and tunes transmissions. He said the HD 6L80 will probably make me happy as is. But after break-in, he'll make any adjustments I want for free. I like this a lot, because while the BB tune was a game changer, I wasn't entirely happy with the 2-1 downshift being so harsh. It'll be good to have someone local I can take it to for tweaks. Besides, now that BB doesn't honor their lifetime tunes, I've got no loyalty for them anymore. This whole thing sucks to be happening when I'm in the middle of moving. But I'm glad to be fixing this right, getting a bit of an upgrade, and getting some overdue maintenance done.
First question: what cooler should I get? I see recommendations for several.
Second question: the transmission guy says lots of tuners jack the line pressures up and kill the pumps early in the 6L80. He said he'd look at the BB tune to see what they did. But he thinks that might be why it died at 140k (tuned since 99k). I've never heard of a BB tune killing a trans. Do you think there's any validity to this? I wouldn't be so quick to blame BB. If anything it's an indirect cause, as my right foot would have had a lot to do with it.