I have a 2008 Acadia, which I rebuilt the engine. In testing it out, I've found the TCC locking and unlocking constantly at mid throttle and cruise. On moderate acceleration, once it hits 3rd gear, it almost feels like it is bucking it is locking and unlocking so much. I've confirmed that it is the locking and unlocking by disabling it all together, then it shifts and drives beautifully. I've done a lot of research and found a lot of people having the same problem with cameros and solving it by increasing the lock pressure or pwm percentage using hptuners. But I don't have that option with efilive. I've also seen where people use a different TCM OS and that has fixed the problem. But I don't see anywhere or anyhow to do that.

I don't have hptuners and have never used it. I've used efilive to change transmission tuning on a 2004 Chevy Express (made it feel like I doubled the engine HP, and increased mileage), on my 2006 2500 duramax, on my brothers 2005 2500 duramax, on my dad's 2008 6.0l gas, and now this 2008 Acadia. Every one has turned out great, increasing the mileage, making it feel more powerful, and making it more enjoyable to drive. The acadia felt very underpowered to begin with, but is good now. I tried changing the desired slip to 0. I also tried changing the TCC ramp pressure, but only a little. I increased the whole table 50% which didn't change most of the table much, everything was low numbers to begin with. Then upped the numbers in low slip (5-40 rpm) to 5-17 kpa/s where stock was 0-10 kpa/s. It appears that this is a table showing desired rate of pressure increase, rather than applied pressure, so I left 0 rpm slip at 0 kpa/s. This appears to have only made it lock and unlock faster and more aggressively. I disabled the TCC in all but 6th gear in normal mode, and my shift points keep it out of 6th gear until over 65mph. I am using tow mode and the tap shift to check how my changes are affecting the TCC lockup.

Has anyone been able to fix this problem through efilive? Is there a way I could try another TCM OS?

One last thing is, I bought this vehicle with the timing problem at 191,000 miles. Body and interior were in good shape, so I spent a pretty penny rebuilding the engine and replacing all the wear parts (brakes, struts, etc) hoping that it would be good for a long time to come. But I never drove it before I did all the work. I did flush the transmission as soon as the car was back in one piece, then it got a fluid change after 1 hour of running, then it got another fluid change when I pulled the engine back out to fix a rod bearing after it spun with 200 miles on it. Flush and first change were using AcDelco Synthetic Dex VI, but this final fill I went with Amsoil Signature Dex VI. Now I've got another 200 miles on it and this appears to be the last problem left. I can not guarantee that it is not a physical problem with the TC, but I would bet that it isn't based on everything I've seen, felt, and heard.