4L65E 2-3 Shift Flare on Part Throttle Up-shifts (WOT is fine)

[arbartz95]

Alright, so this very well just might be that it's this 4L65E's time to go, but I wanted to at least run it by you guys first.

Vehicle is a 2004 Silverado SS with 190k miles on it.

I'm experiencing slight shift flare on the 2-3 shift, but only under low part throttle up-shifts, and it gets worse as trans temps climb, however at WOT the 2-3 shift is fine. 1-2 and 3-4 shifts occur just fine at both part throttle and WOT. The truck has 190k miles on it, but I'm not sure if the trans has ever been reworked. It has a new transfer case, so who knows.

So far I've played around with increasing the 2->3 Pressure Modifier table and the 2->3 Shift row in the Upshift Pressure Multiplier table, but it hasn't appeared to have helped.

Attached is a short log showing a couple of part throttle shifts and a WOT shift, along with the tune file. I can gather more logs tomorrow if there are other parameters I should be logging.

2004 Chevy Silverado SS - ShiftTune_v6_2-3upshiftpressuremultinc25per.hpt20200204 - 2004 Silverado SS 2-3 Shift Flare.hpl

Thanks,
Austin

[mbray01]

messing with the pressure modifiers isnt going to get you where you want to be, you need to be adjusting the actual pressure tables and shift times. pay attention to what calculated torque you are seeing when it happens and increase the pressure by 10%, and lower shift time by 10%. make sure that your adjustments are smooth in the tables, you dont want peaks and valleys on the 3d table. example if your seeing an issue at 220tg, adjust table from zero through 220, then transition it out through the next few rows. Smoothing and interpolation works, but pay attention it can walk settings back down, or force it too far forward

[arbartz95]

So even though it shifts fine when the trans temps are cold, I should still be working with the base pressure tables and shift time targets? It seems a bit counterintuitive to me, as the issue gets worse with temperature, and I already like how it shifts currently (it's a truck, so I don't need/want super hard shifts), so I figured that modifying the temperature based tables is the way to go.

I will however give it a shot tonight and see if it helps. Thanks for the input!

[mbray01]

in my experience with the pressure modifier tables, is it tends to take extreme changes to create small results. I tend to try to get everything in line with the base shift pressure tables first. usually the only time i really use the modifier tables, is if i have one kicking into 2nd really hard, the modifier tables seems to help the greatest with that. Also pay attention to your force motor current table. Just throwing numbers at that table can be bad, however small adjustments in there can make a huge difference in shift quality across the board with the transmission. That table is heavily weighted with transmission temperature. Some cals have just a positive table, and some have a negative table. if you have both, just copy your changes to both tables