6l80 Shift Evaluation

[ns158sl]

Just trying to piece together how a guy should interpret shifting on a 6l80. I have been trying to search and study on what to do with a 6l80 but cant find much on what should we be looking at, or more so, how to troubleshoot different shift patterns. One thing I will say is my current cal pulls too much timing out during shifts, but I am not committed yet to pull TM. I know a few say it can be removed/adjusted, but i am trying to find another method. I just know Ive ridden in a cammed 8 speed truck without shit for TM removed and that shifts like a PDK... well throttled upshifts, lol.

I have a quick log, 2:56 is a wot shift and 7:43 is a lightish throttle shift. Any insight on how to interpret the shift would be great.

Thanks!

[5FDP]

I always have my 6L80e's pull that much timing. I set my base minimum timing or whatever to like -8 degrees, I want it to yank that timing away for a split second to help make the shift happen. The part throttle shifts won't go as low but at full throttle I have it go negative.

[ns158sl]

I only say that because the "seat of the pants feel" there is a delay, even though the shift time is matching desired. Mostly curious seeing and figuring out how to adjust the "slope" of the shift.

[5FDP]

Can you post the tune?

In my current silverado I don't really have any delay or hesitation type feeling, it just hits off every shift like I want it to.

[ns158sl]

Definitely. Not looking for fix my shit but more so looking for how to analyze a shift in the scanner. This is not a stock vehicle either.

[5FDP]

I think your shift time settings are good. I have my 0-177 ft lbs a little lower than yours, at around .3300ish and the higher ft lbs at .3000 like yours.

Shift pressure and on-coming settings are good in my opinion.

I still think I would raise your base minimum spark to have a max of -8 degrees of timing pull instead of -25. I also raised my torque mngt minimum spark from -20 to more around zero. I personally zero out burst knock too and I raise my torque mngt torque limit vs rpm for each gear on the engine side way up just to make sure that isn't getting in the way.

[TransGo Robert]

Just trying to piece together how a guy should interpret shifting on a 6l80. I have been trying to search and study on what to do with a 6l80 but cant find much on what should we be looking at, or more so, how to troubleshoot different shift patterns. One thing I will say is my current cal pulls too much timing out during shifts, but I am not committed yet to pull TM. I know a few say it can be removed/adjusted, but i am trying to find another method. I just know Ive ridden in a cammed 8 speed truck without shit for TM removed and that shifts like a PDK... well throttled upshifts, lol.

I have a quick log, 2:56 is a wot shift and 7:43 is a lightish throttle shift. Any insight on how to interpret the shift would be great.

Thanks!

You must have attached the wrong file, that log only has light to medium throttle upshifts. They all look good to me, but no WOT shifts in there to look at.

[ns158sl]

Woops, I must of lost my WOT log. I have a short one where it is at WOT for the 3rd gear shift. That happens around 50 seconds. Thanks for taking a look. Trying to figure out the "ramp" of the shift and what else I can do to improve.

[TransGo Robert]

Man that's one bad 2-3 shift, careful if you do too many of those WOT you will quickly wipe out your 3-5-R clutch pack. Unfortunately I am a transmsision specialist, not a tune guy at all so I don't exactly what is setup wrong in there. Normally I would just have you install our TOW&PRO kit, set up the torque adder tables to what we say and be done with it. But there is a way to make the shift shorter with just with the tune, I know that, I just don't know how to go about it. I am on here to help and also to learn more about this tuning side of things. Line is commended plenty high, but when it commands the 2-3 you can see that the shift starts when PCS 4 drops to zero, but it is not a complete shift, the ratio is only 1.754 to 1, so it is slipping baldy. Then PCS2 ramps up slooooooowly and it finally drops to the 3rd gear ratio of 1.53 about 0.4 seconds later... that whole time your 3-5-R clutch pack is slipping. hh.png

[ns158sl]

Oh god ouch, lol. I thought that one felt funny. It has the competitor's (sonnax) added clutch in the 3-5-R. Im starting to wonder if I should be going after the Turbine speed tables vs just the desired shift times. Thanks again!

[hjtrbo]

It is nasty that 3-4 shift at 3m01s, saving grace is you're at extremely light load. Later on in the log at 7m16s when you've got a bit more load on she's fine. Overall she's pretty lazy at low load. Suggested settings attached.

Screenshot 2023-10-02 095942.png

[ns158sl]

Thanks hjturbo, I will put that in immediately lol. I guess I can up pressure a little more for the 3rd gear shift but I feel like there should be enough there?

[hjtrbo]

Rob has said your line is good.

[hjtrbo]

Rob has said your line is good. See how the -30 and -100 torque row changes go. If it feels like it's dumping into gear when off the gas then you can reverse those changes. Shift time and feel tuning is very subjective to the individual.

[ns158sl]

Just to update. I reset adaptives becuase I couldnt remember last time I did with trans adjustments. Well now it shifts quick and stiff. I will have to put to more miles on it to see if it stays or adapts pull it apart.

Im still trying to figure out how to interpret the data fully. If anyone is interested, SIU (Southern Illinois University) and https://www.automotivetextbook.com/ on youtube has put a scope and transducers on the 6l80 to figure out how tables correlate with actual pressures. I wish someone that can read HEX or just general GM ECM data would help that dude. He knows trans hydraulics and powerflows more than most, maybe not ECM and HEX data.