Transmission problem and rear window leak

Carroll Gilliam · June 21, 2015

Transmission down shift rough.Recall on reprogram torque converter mod. I went to dealer and they did this reprogram, recall and my truck shifts rougher than it did before I took it in. They didn't give me any paper work or have me to sign anything. I called them back and told them it was worse. The service manager said it had to relearn my driving habits. I don't think I get as good of gas mileage afterwards.2015 high country 6.2 , 8 speed crewcab.

TJay74 · June 22, 2015

They are correct, when the module is reprogrammed all of the shift logic that was learned is erased and has to be learned again. It will take around 500-1000 miles for the shift to clean up. Personally when my truck was flashed I drove it gentle for the first set of shifts, then once the truck was warmed up I made to go WOT and let it run thru the 1st 4 gears up to highway speeds on the highway, like when I can jump on it getting on via the on ramp.

After that I drive it normal, mine has shifted fine anytime I have done that process on the last 4 GM vehicles with the 6L80E transmission.

80vette383 · June 30, 2015

As an update, I had still been waiting for the glass that was ordered. I finally called today and my service writer said "can you believe it? the glass just came in!" ....yeah, ok. While talking to him, I explained that in the time that I've been waiting there has been a ton of water getting in. I expressed my concern that headliners tend to sag and deteriorate over time after repeatedly getting wet. I said that I wanted a new headliner. He agreed to replace the headliner, so now I'm waiting for that to be ordered. Hopefully they install it without issue.

As far as the rear window being a "recall", I had asked him several times whether it was a recall or TSB. He was adamant that it was a recall, but I had been unable to find anything related to this issue and a recall for it. Finally today I asked him for the recall number, and now, low and behold, it's actually a TSB, NOT a recall.

Either way, hopefully some day soon I will be getting my rear glass and headliner replaced. Until then I will continue to have a faucet running from my headliner when it rains.

Randys Denali · July 7, 2015

I got my 2015 Sierra Denali (6.2L, 8 speed, 2WD, crew cab, 6.5' bed) on November 5th 2014.

In December 2014, my navigation system started showing me driving 50 miles away from my actual location and the onstar stopped working. It took a few weeks to get new parts, but they had to replace my entire main computer that handles the nav and onstar.

Approximately January/February 2015, my transmission was jerking when I would come to a stop. It feels as though it's holding on to 2nd gear until I come to a complete stop and then it jerks it into 1st gear and jolts my truck forward. There is also a audible clunking/banging noise coming from the transmission when this happens. ----- I took my truck in to the GMC dealer and they explained they explained they applied an update to the 'transmission control module' (but the technician also . That seemed to get rid of the problem. SIDE NOTE: When I took my truck in, they did not drive the truck or have me drive it with a technician riding along to understand what I was describing. They simply took the truck into the bay and reset the 'learning' feature on the transmission. After they applied the update/reset the learning feature, I drove the truck with a technician and I confirmed the problem was no longer noticeable.

Approximately early June, I took my truck in for an oil change, at which point I was notified of a recall on the 'Torque Converter Clutch'. They fixed the recall by applying a update to the torque converter clutch and that caused the problem to reappear in my transmission again. I took my truck in this morning to have it checked out again. I asked for a technician to drive my truck prior to fixing anything. The technician stated he did feel what I am talking about and wasn't immediately sure of what could be causing the problem. I was told they don't have time to find out what the problem is today and was asked to come back in two days when they have time.

The transmission is great up-shifting and down-shifting on all gears from 2nd through 8th gear. 1st gear is the only time I have issues. What i'm getting from my own experience and from what I've read from other peoples experience, they don't do anything to fix the transmission problem. They just reset the learning feature and after every couple thousand miles, the problem will keep coming back.