Transmission might be toast.

11bDad · May 23, 2016

At the very least you wont get the p050d code from the injectors. That seems to be popping up left to right these days. Good luck, mine is at the dealer now having injectors replanced.

True, but to my knowledge (and the workorders), the only codes stored during this whole fiasco were P0700, and P0741. The tech did note that misfire in the injectors was found, but did not mention a code being stored.

newdude · May 23, 2016

Dropped the truck off at the other dealer yesterday, and had a very encouraging test drive & 20 min. conversation with the tranny tech. He was very attentive, went over all the previous dealer's work orders, asked questions, and seemed very confident that they could handle the repair. He said considering what had already been done, GM would probably give him approval to disassemble to the point of failure, prepare an estimate to repair, and if it came within $600 of replacing the tranny, then they would authorize replacement. Guy has been doing this for 40 yrs, so I'm sure my issue is something he's seen before. Stay tuned.

Sounds like they need to remove and inspect some hard parts inside that transmission. GM is aware of the 4-5-6 clutch hub breaking on 2015-2016 6L80 transmissions. We had one in for this at 500 miles. He had 1st through 3rd fine, as soon as it wanted 4th gear she just revved up.

07Softail · May 25, 2016

14's are included as well correct on the 4-5-6 hub cracking right? Also from what I have heard from a trans builder that is with a GM upgraded (revised) drum, but i surely can't confirm that though. These transmissions are a mess IMO... Black Bear has been working on mine for months and we can't get it to firm up the shifts hardly any. I think mine was a lemon from the factory.

RT

11bDad · May 26, 2016

Checked in with the dealer yesterday, and they said tranny guy had ordered a new torque converter and pump. Hopefully they'll have it ready to go tomorrow and that will be the end of this ordeal.

11bDad · May 28, 2016

Twenty five mile drive home from Dealer #2, and the truck feels good. Haven't hit the interstate, but I'll get that in later today. Replaced converter, pump, filter, etc. Work order noted metal in pan. The fluid and filter had been changed 157 miles earlier, when Dealer #1 replaced the TCM. Converter was blue, and pump cover "scoured". The rental I turned in was a 2016 1500 CC SB LT (5.3), and handled like a 3 legged goat compared to my truck with the Z60 pkg. Hopefully this the last of the tranny dance. Later

Came across this video explaining the inner workings of the 6L80, which I found quite informative.

cNate · May 31, 2016

This happened to me in my 2009 Suburban LTZ with a few thousand miles on it. At least they're working on it, I took mine to a few dealers way back then and they told me the tranny was slipping but they couldn't do anything until it's actually broken. Drove it like this until it hit 5k miles and then the tranny went completely. The truck was 6 months old with 5k miles at the time and sticker was $65k! That suburban had a long list of failures (DVD/Nav unit, heated seats, etc.) and I dumped it about 10k miles before the extended warranty was up. My Sierra has been much more reliable through 25k miles.

Point of my story is sometimes you just need to fully break it to get these guys to fully repair it under warranty. Hope the torque converter and pump do the trick! Good luck!

11bDad · May 31, 2016

Drive into work was uneventful (thankfully). Noticed at 70 mph, the tach is approx 150 rpm lower than before this whole mess started. Initially, everything feels good. Since there was metal in the pan, the tranny tech completely disassembled, cleaned, and reassembled the whole transmission in addition to the new converter and pump (plus a new TCM & 6 new injectors from Dealer #1).