Noizyboy

I have a 16 Sierra WT Whipple 5.3 and 3.08 gears with rebuilt 6l80e sonnax billet shaft and 456 HD clutches. 660whp and stg2 pds cam. Issue has been around before rebuild, and have had it happen with LSA converter and my 3k stall converter. My tuner and I have build many ls/lt cars, yet I am not too savvy on transmission stuff. Nor do I know my way around HP tuners.
Winter time it shifts badass after starting up and leaving the house. Boom boom boom hitting gears like a 10spd, just shifts and gets into power band immediately. THEN after 2 or 3 stop signs and still 65-100°F it begins to start flaring, everytime it carries to the next gear it drops 3-500rpm, then catches back up to where it should have been. You can feel the delay, almost like it falls on its face for a second, then comes back. If I'm taking off at a stop sign or green light, sometimes it feels like it's taking off in 2nd. And won't actually MOVE til 2500-3200rpm.
It's an ongoing issue. Tuned so many times. Spent 9k on rebuilding this trans over and over. There has been a few times in summer, after driving all day, it begins to shift badass again. This power ain't doing me no good with this issue. I'll try to post links for videos.

Battery 4yrs old
cleaned grounds
fresh lt4 fuel system
E85 and 93
Boost or no boost
Fluid still red looking great and new techM

https://youtube.com/shorts/Lfk6pc83Ptg?si=VJlxEuZh2rvfSPLf

smokinlmm

TEHCM is probably bad or has a torn seal. I just went thru this, did you rebuild your tehcm or buy a new one? I also had a bad trans pump valve that caused a similar issue, it was not casted properly. I chased this for a long time, In the process I also found an oversized hole in my separator plate. I just bought a new valve body and put the circle D kit in it. I’m not sure which issues was causing the flare but once I threw those parts at it it quit flaring and shifts perfectly now.

You need to call Brandon @A&B performance. He figured mine out and it was a bastard, he had it out 4 times.

Noizyboy

Where is A&B performance? Did you have pics of any of the issues? And what exactly was yours doing all together? Also TechM was new from dealer 2 times.

smokinlmm

Flaring shifts after it warmed up. It would not make the 2 3 shift properly even under light throttle. It was just unpredictable, half the time it would hold and shift and the other was like it was burned up when it was fresh. I have had that thing rebuilt 3 times now and finally have it right. Brandon is in Wilmington NC, he has a ton of knowledge about these transmissions. Works directly with Circle D and knows their kits backwards and forwards. He does not jack up line pressure or mess with shift strategy. He is able to setup the trans to hold without the usual bandaides which cause issues down the line. My trans tune was terrible,it had line pressures all over the place and we found a plug in the pressure relief for the pump. If your having trouble take it apart and go thru it thoroughly, I’ll bet you find a few problems like I was having that were compounding your issue. Or do as I wish I would have the first time and buy a new one from gm and put the kit into it and roll out. That would have saved me a ton of money and time if I have done that the first time.