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Thread: 8 Speed Truck - 3-4 shift flare when cold

  1. #1
    Tuning Addict WS6FirebirdTA00's Avatar
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    8 Speed Truck - 3-4 shift flare when cold

    Guys,

    See the attached log at 1 minute 36 seconds into the log.

    This is the 3-4 shift and right before it shifts and hits 4th the RPMs flare up about 300 RPM. I noticed this in the new TCM, also in the old one. The old one I have a log of it doing it on the 2-3 shift.

    It only does it cold and I have only seen it do it cold leaving in the morning. It does not do it when I leave work in the afternoon, but I also don't take the same path obviously.

    Anyone seen this before and have any recommendations? I know there is a TSB out there for fluid change (only 4400 miles on the truck) and also see others note some of the adaptive features may have learned something wrong. Not sure if a reset and fast learn would be helpful. I did do a fast learn after the TCM swap and new tune.

    Scratch that, log won't load. Not sure if it is too big or what but I will try again or look for another. I did load some screen shots.
    Attached Images Attached Images
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  2. #2
    Tuning Addict WS6FirebirdTA00's Avatar
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    One thing I noticed is the TCC line pressure is zero.

    What controls TCC line pressure coming on from cold start?
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  3. #3
    Senior Tuner Russ K's Avatar
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    The TCC will not apply until the trans fluid temp is warmed up. As for the cold flare, try adding to the temp offset table.

    Russ Kemp

  4. #4
    Tuning Addict WS6FirebirdTA00's Avatar
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    If I add to the offset table, being the 3-4 shift, do I add to the 3rd gear table or 4th? I am not too sure after reading the table descriptions.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  5. #5
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    Could be internal leak in 2-3-4-6-8 and 4-5-6-7-8 Reverse Clutch Assembly. If under warranty, dealer can apply new fluid and flush bulletin and adapt learn. Then repair if not corrected. Reducing clutch fill rate or reducing shift times may or may not help. Typically have not seen flares in upper gears, but TCC shudders and poor 1-2 cold shifts due to poor cold fill and/or torque converter bleed down in 2015's. New pump to correct. 2016-2018 better , but still need new fluid flush and possible cal updates. I sent you the new bulletin thru another post.

  6. #6
    Tuning Addict WS6FirebirdTA00's Avatar
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    Thanks again for the info. I only get the flare cold and only certain cases. I am trying to narrow it down.

    I am working on finding someone I can trust at a local dealer to do the flush per the TSB. I was wanting to put a different pan on here to make future work on draining the transmission easy. Doing it on my own time and not having to leave the truck is worth the cost for me. I have been wondering if after doing that with another flush or two if it was a good method to swap fluid. I need to read back through the notes on the process.

    I was going to reset the adaptive learn and do a fast learn (not sure how this varies from the dealer). I have seen some mention this. The fact that the old TCM did it 1 or 2 times on 2-3 and this one is 3-4, maybe something was incorrectly learned.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  7. #7
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    The dealer has or will have new adapters to flush thru pan and out thru trans housing. It's 4 quarts at a time repeated 4 times. It requires the GM flush machine which is air pressurized. The cooler gets flushed in both directions. Texas is one of first states to get fix released due to temperatures. I think there are something like 11 hot climate states that get it first. I have done two myself two days in a row. It will then take several hundred miles to work the new fluid into the plates and TCC to know if it's corrected. Initial test drive is definitely improved. GM has put time into this. They are stating it's a fix, but your not going to ever have a perfect shifting 2015-2017 8 speed. You can only do so much with calibrations and flushes. Go for a 2018 10 speed. Cadillac Escalades have them. Not sure about Chevy/GMC. There is no comparison.

  8. #8
    Tuning Addict WS6FirebirdTA00's Avatar
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    To be honest, other than that flare I really like how mine shifts. I am going to look at shift times, I think the 3-4 can happen so fast and/or since 4th has the lowest base line pressures - it struggles to adapt.

    When I get the flare 3-4 shift happens in .18 sec. command is like .4 or something with line pressure bases at 50ish. It is lower than all other gears and by a high percentage. I haven?t messed with it since I don?t know why the base pressures are lower in 2/4/5/7 at 1000 and 2000 RPM compared to the others.

    I fixed the hard 1-2 shift, cleaned up other sloppy shifts, the TCC lockup is much smoother giving it a little more slip RPM at 1200 rpm on the turbine speed in gears 1-3. I didn?t like the steep change from 20 to 10.

    The only other thing I notice is the negative torque shifts at times. After a hard accel the upshifts at no throttle can feel clunky at times.

  9. #9
    Tuner in Training chameleon's Avatar
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    Quote Originally Posted by WS6FirebirdTA00 View Post
    To be honest, other than that flare I really like how mine shifts. I am going to look at shift times, I think the 3-4 can happen so fast and/or since 4th has the lowest base line pressures - it struggles to adapt.

    When I get the flare 3-4 shift happens in .18 sec. command is like .4 or something with line pressure bases at 50ish. It is lower than all other gears and by a high percentage. I haven?t messed with it since I don?t know why the base pressures are lower in 2/4/5/7 at 1000 and 2000 RPM compared to the others.

    I fixed the hard 1-2 shift, cleaned up other sloppy shifts, the TCC lockup is much smoother giving it a little more slip RPM at 1200 rpm on the turbine speed in gears 1-3. I didn?t like the steep change from 20 to 10.

    The only other thing I notice is the negative torque shifts at times. After a hard accel the upshifts at no throttle can feel clunky at times.
    seems like we are both after the same thing, how did you fix the 1-2 hard shift ? at slow accel its smooth but pulling off from a light at quarter throttle i get the jerk, WOT its getting better but the quarter to 50% throttle is where im at most of the time so its the most annoying.

  10. #10
    Tuning Addict WS6FirebirdTA00's Avatar
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    PM me to remind me if I don?t post, but when I get back on the PC I will post what I did.

    What I am quickly learning is too high or too low of shift time causes issues. Too fast it bangs the gear trying to go fast, too slow and it hangs a while and then jumps in.

    My shift times in the top row are 0.450-0.600 and up to 225 Nm (sorry I am in metric) it tapers to about 0.350-0.400 I think. Then I speed it up to 0.275/0.300 at wide open. I still have TM on. I went up 1 point on the inertia tables, but back down 2700 and lower and 300 Nm and lower.

    Again, I will post what I did when I get on. I also put the TCC slip up to 15 from 10 at 1200 RPM for 1-3.

    Right now I am trying to dial in the 2-3 between 3000 and 4000. I am trying not to hit it hard, but I got a little slow and it feels like it is hesitating for a split second.

  11. #11
    Tuning Addict WS6FirebirdTA00's Avatar
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    Alright, so here is what I changed for 1st and 2nd gear:

    • Inertia for upshift
    • Part throttle upshift (normal)
    • Shift timing
    • TCC desired slip AC off


    I attached some screen shots of what I did. Here is some of the logic:

    Inertia for upshift:

    1st gear inertia.PNG

    From everything I read, the adaptation on these transmission and the inertia table drives what it really wants to do. What I am seeing is the other tables need to fall in line or it gets screwy. I need to see how the truck does in the AM, but the 3-4 flare we not in my log this morning. The only change was shorter shift times. I figured the higher inertia tables over stock may have messed with what was good and made it bad. On the other hand, stock the 2-3 flare was there and the higher inertia and shorter (much shorter vs what I did on 3-4 since it was 2-3 and I was ok with a more firm shift, based on how I wanted to speed up the shift) shifts seemed to fix it.

    So my theory (if I don't see flare in the AM, and I probably will haha) is the trans was setup to shift fast. The target time didn't match what it could do/wanted to do so it was trying to adapt and reduce pressure. Since the shift was happening fast and it could not really slow it down, I suspect that showed in flare. I went up on inertia last night for the 3-4 and I even saw some flare warm. One solution may be going back to stock inertia, which is why some likely don't want to mess with it, but then I see the base line pressure do very little. I went on a ride the other night with some changes and I would have bet $1,000,000 nothing changed. Looking at the logs for trans PIDs I didn't see much of anything change on WOT 1-2 and 2-3 shifts.

    Part throttle upshift - normal:

    part throttle upshift normal.PNG

    I had a few areas I tweaked to get in a higher gear cruising, but mainly 1st gear I raised the upshift. Thinking back to inertia, I don't think there was physically enough for some of the upshifts at low speeds. Raising that shift point really helped the pulling out of the driveway cold, parking lot on and off throttle near the shift, etc. Shift time played a big role here too, but the speed did help. Not to mention, I hated the fast shift out of first at low TPS. It was a PITA on u-tuns and takeoffs after turning where I wanted to accelerate quickly.

    Shift timing:

    1-2 shift time.PNG

    My 1-2 and 2-3 were the same until today. I decreased the 225-300 Nm for 2-3 because I felt I was approaching some flare. It was hard to pick up, but I could feel it in the 3000 RPM range. I increased the time in first because it was still banging gears hard there. I have been all over with this table and this time has a good balance of quick shifts at high loads without feeling like you are going to snap something, but good transition time at low to no throttle.

    TCC desired slip AC off:

    TCC slip AC off 1st.PNG

    I did this for the first 3 gears. I hate when the converter went to lock up I lost RPM and the acceleration. This was a better transition from 1100 to 1200. It also helped 3rd from bogging so much and not having to kill the shift schedule tables to be in 2nd gear. This may be more preference than required and I am still playing around with the TCC setting to avoid the sluggish feel, unbalanced lockup ramp and odd unlocks before shifts at low speeds that then feel like flare. The apply and release tables will need to be tweaked with this, but I have not spent a lot of time here yet.

    I just wanted to share what I did. I would be interested to hear feedback or see if it nets the same results for any others. After the TCM swap I did the fast learn and have not repeated since. As good as it feels right now I am hesitant to reset the learning and redo fast learn. Granted, over the next few days it could adapt and put me back into trouble in some spots, but we will see. I am mainly going to focus on the shift times and blending the inertia to get the feel I want. Once that is stable I will work on the TCC, shift speeds, etc. to make other improvements.

    I just got back into this new torque based stuff and really digging deeper into autos in the last 3-4 months. My world was Gen 3 LS1 (80%) and some Gen 4 (20%). I stopped tuning on the side because I didn't have time for the hobby and the WS6 was dialed in and the mods stopped - then I pulled the motor due to a leakdown issue I had been running in for about 8 years lol

    Take this for what it is, I bunch of half baked ideas. If anyone see something I am just completely wrong on or talking in the wrong direction, please speak up and call me out on it. I am not trying to mislead anyone and I am not trying to claim I am any sort of expert. If I rate my confidence with the LS1 manual stuff at an 8 our of 10, I rate this at about a 2.
    Last edited by WS6FirebirdTA00; 01-26-2019 at 09:15 PM.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  12. #12
    Tuner in Training chameleon's Avatar
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    Quote Originally Posted by WS6FirebirdTA00 View Post
    PM me to remind me if I don?t post, but when I get back on the PC I will post what I did.

    What I am quickly learning is too high or too low of shift time causes issues. Too fast it bangs the gear trying to go fast, too slow and it hangs a while and then jumps in.

    My shift times in the top row are 0.450-0.600 and up to 225 Nm (sorry I am in metric) it tapers to about 0.350-0.400 I think. Then I speed it up to 0.275/0.300 at wide open. I still have TM on. I went up 1 point on the inertia tables, but back down 2700 and lower and 300 Nm and lower.

    Again, I will post what I did when I get on. I also put the TCC slip up to 15 from 10 at 1200 RPM for 1-3.

    Right now I am trying to dial in the 2-3 between 3000 and 4000. I am trying not to hit it hard, but I got a little slow and it feels like it is hesitating for a split second.
    gotcha im in the same boat, only issues right now are 2nd is always unpredictable and 3 hiccups a bit.. 4 and 5th are like glass.
    I have tried a ton of back and forth methods, spent an hour on it today and ultimately raising the shift pressure helped 2nd a bit and slowing down my shift times (had em too quick)
    ill shoot ya a PM!

  13. #13
    Tuning Addict WS6FirebirdTA00's Avatar
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    What are the main issues you see in 2nd and 3rd?

    How much did you change the shift pressure and where? I really didn't see much in what I did.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  14. #14
    Tuning Addict WS6FirebirdTA00's Avatar
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    I need to post the driver demand table too and the torque management in the ECM. That really helped low speed takeoff too where it drops lke 90% demand around 10 MPH or so. I feel that helped the low speed 1-2 gear feel as weel. It also helped first actually go when you hammer the throttle.

    I was trying to do some pulls to 60 and before doing that if I hit it in first with traction off it took over a second for the throttle fully open even though the pedal was 100%. The TM fixed that and the driver demand fixed the mid throttle takeoff.

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    Tuner in Training chameleon's Avatar
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    Quote Originally Posted by WS6FirebirdTA00 View Post
    I need to post the driver demand table too and the torque management in the ECM. That really helped low speed takeoff too where it drops lke 90% demand around 10 MPH or so. I feel that helped the low speed 1-2 gear feel as weel. It also helped first actually go when you hammer the throttle.

    I was trying to do some pulls to 60 and before doing that if I hit it in first with traction off it took over a second for the throttle fully open even though the pedal was 100%. The TM fixed that and the driver demand fixed the mid throttle takeoff.
    Yea not a bad idea, then you have tons of people say they next touch DD and have no issues.. but i had to massage it.. it had way too much dead pedal when cruising past 60mph.. you really had to floor it to get moving, what i did find is that the larger of that dead pedal helps you get the proper cruising pedal for gas mileage, when that is decreased its a smaller window for it, BUT the responce is way better!

  16. #16
    Tuning Addict WS6FirebirdTA00's Avatar
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    Well, I ended up having another time it flared up, so scratch that...

    May just cut my losses here. Like mentioned above, could have to do with the fluid swap too.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  17. #17
    Advanced Tuner IARLLC's Avatar
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    WS6, Thanks a lot for all you shared on this! Very hard to find good info for tuning these. Any updates on it? Curious about your DD and TM tables. I really don't want to mess with them much until I see how you handled them.
    Thanks again!

  18. #18
    Tuning Addict WS6FirebirdTA00's Avatar
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    I will try to remember and start up the laptop to take some shots of those tables. I didn’t do anything major. I mainly adjusted the DD tables in areas I felt it was lazy at low speed and also smoothed out some weird dips. I want to spend more time on it, but after I get the flare resolved. It comes and goes, I think it is some adaptive stuff changing it. I am going to swap to the newer fluid first before I go too crazy. The only complains I have right now are really the low speed/cold trans temps. It isn’t as bad as stock was, but the flare is annoying and I feel some surging at times. I am letting it get more run time with the current tune so the adaptive stuff can level out.
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)

  19. #19
    Advanced Tuner IARLLC's Avatar
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    Thanks for responding. I am really curious what needs done with TM on these. One totally respected expert says to remove it in a couple sections on these 8L90E....and I believe him of course. I have tended to leave TM alone on the torque based GEN4 and GEN5 rigs though since I am not sure and don't want to damage peoples' rigs. Sounds like you were able to get a noticeable improvement on yours though.

  20. #20
    Tuning Addict WS6FirebirdTA00's Avatar
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    I am in the same boat. I can still tell some TM on the shifts, but I can live with it not fully understanding the risk. I am not trying to build a race car/truck here, so I am looking more to optimize and improve reliability. If TM being on hurts this, I may be more tempted to disable.

    Here is the driver demand table. I still want to do more work at the low throttle/mid rang speeds. There is still a transition near 3rd gear at low throttle you can feel the throttle being pulled back without moving your foot. I confirmed this in a log too. This did clean up some other odd areas on me, but the changes are minimal. I at least have more confidence the direction I am heading is improving without being any risky changes.

    driver demand.PNG
    2000 WS6 M6 (motorless.....and last thing I have done for tuning in 7 years)
    2018 Sierra SLT 5.3L A8 (trying to learn all the new Gen 5 tables and methods)