I have a 2004 Denali and it has about 50,000 miles on it and it started to get a flare on the 2-3 shift. It still has the factory warranty so i took it in 2 wks ago. The dealer did a complete rebuild and put in a new valve body. Picked it up yesterday and bam same damn flare! After all that messing around it still flares the 2-3 bad! They told me to drive it for 2 wks and let the computer "learn" the new shifts! Thats a bunch of b.s. if you ask me! What causes the trans to flare? Is it low line preasure? If so could a custom tune add more line preasure to the 2-3 shift and be done with it safely? I don't want a band aid i want a fix! Any help would help me!

 

When you say "flare", what do you mean exactly?

1. above normal raise of RPMs during 2-3 shift?
2. does it engage 4th gear at all?
3. is 1st fine, 2nd fine, shift to third shoots RPMs above 3K RPM (similar to question 1)?

Answering this should help give others a better idea of what you're experiencing.

 

It does take time to learn what is called taps, but you shouldnt have a flare from 2-3. Raising line pressure might help some but tis will be a bandaid and just cause you headaches like hard shifts in other gears, and garage shifts.
My suggestion to you is go back to the dealer and talk to the service manager and get him to go ride with you and show him whats wrong. If you you get no satisfaction from him, go tot the sales manager, trust me you stomp your feet enough and something will get done on e way or another.