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Thread: WOT Shift Speed vs Shift - Normal Table questions

  1. #1
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    Post WOT Shift Speed vs Shift - Normal Table questions

    Hello,

    I have two questions regarding the WOT Shift Speed vs Shift - Normal Table.
    Here are the parameters:

    2>1 | 19
    3>2 | 36
    4>3 | 59
    5>4 | 76
    6>5 | 107
    7>6 | 313
    8>7 | 313
    1>2 | 23
    2>3 | 42
    3>4 | 63
    4>5 | 81
    5>6 | 94
    6>7 | 313
    7>8 | 313

    Question 1:
    How is the transmission supposed to upshift 5>6 @94 MPH and downshift 6>5 @ 107 MPH ?
    Did the tuner make a mistake with this setting ?

    Question 2:
    With these settings, will the vehicle ever go to 7th or 8th speed at WOT ?

    Thank you!

  2. #2
    Advanced Tuner IARLLC's Avatar
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    1: Yes
    2: No

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    This modified tune is from a 2015.5 GM truck with the 6.2L (L86) engine and 8L90e transmission. 7th and 8th gear are disabled to make sure that the truck never goes above 143 MPH.

    However I still don't understand why they would program the 6>5 (112 MPH in stock tune) downshift at a higher speed than the 5>6 (99 MPH in stock tune) upshift. Can someone shed light on this?

  4. #4
    Advanced Tuner IARLLC's Avatar
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    Yep. Kinda weird. If you stay full throttle past your upshift in to 6th at 99 and keep climbing at full throttle you will get a downshift back to 5th at 112....locking you into a 5-6-5-6 cycle at full throttle I guess. The 2015.5 had a 135mph limit though....

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    Do you happen to know if there is a parameter that you set in VCM editor that doesn't allow the vehicle to go above a certain speed ? If so, could you please tell me where to find it ?

  6. #6
    Advanced Tuner IARLLC's Avatar
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    Under Speedo>Limiter>Limit by fuel the factory set 2015.5 L86 8L90E rigs to 135mph. But if you don't change the trans shift settings you will be stuck in the above mentioned 5>6>5>6 loop at 112 if you hold full throttle.

    If you want to increase the limiter above 135mph you need to also change Speedo>Limiter>General>Source from GMLAN to Calibration....and prepare for the driveline to come apart and abuse the bottom of your rig. If the driveline does not fly out a 2015.5 L86 Yukon Denali will push at least 135 with very mild tuning...not that I would know

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    Thank you for your feedback. I am actually going to limit the max speed to 110 MPH... I don't want the truck to go above that speed.
    I am also going to fix the 5>6>5>6 loop.
    Do you happen to have a factory tune for the 2016-2017 Cadillac Escalade or Yukon ? i am curious to see if the tune addressed this issue from the factory.
    Thank you!

  8. #8
    Advanced Tuner IARLLC's Avatar
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    I have loads of 15 6speeds, 15.5 8 speeds, and 17 8 speeds but, you can't actually read a 17 trans tune....After you have the TCM T87A unlocked and you plug in to read it (you have to be connected to the internet) you just get a standard GM stock trans tune from HPTuners via your internet connection.

    Maybe the repository has a 16 8 speed you can check out. I am getting curious what you will find.

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    Looks like the 17 8 speed has the same settings
    This is pretty strange. Do you think there is a method to the madness ?

  10. #10
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    Actually, now that I think about it...
    2017 L86 8L90E Yukon Denalis (with stock TCM calibration) were hitting a 116mph limiter (probably BCM) with no tuning. Switching the limiter source from GMLAN to Calibration allowed them to hit the factory PCM limit (135mph). I (or whoever was testing them never experienced the 5>6>5>6 loop that the 2015.5 shift tables seem to suggest.

  11. #11
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    OK so I think that I finally understand this. You cannot look at just one table. You need to look at all related tables. You won't be able to find a situation that gets you to downshift from 6 to 5 at 112 MPH. Actually, if you take a look at the Part throttle shift upshit normal table AND the Part throttle shift downshift normal table , you will notice that if you are in 6th gear at 99+ MPH and floor the pedal (100% Throttle Position), the vehicle will hang on to 6th till it hits the limiter.

  12. #12
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    Yes. You are right. The full throttle tables make it look like it will have a 5>6>5>6 loop but I have not experienced that yet. I should have thought back about how many times I have done this. Those part throttle tables explain it. Usually you want them to agree with the full throttle tables but in this case GM probably did not care expecting that 2015.5- 8 speed L86 rigs have the BCM limiting to 116mph. I have some 0-135mph videos on my phone from 2015 L86 6 speeds but I deleted the 2015.5 and 2017 videos. Since I know for a fact that an untuned 2015.5 and 2017 pull straight to 116mph in 5th, I guess that proves that the part throttle table over-rules the full throttle table. The part throttle table shows that (BCM limit removed) you won't get a 5>6 shift until 129. I have less seat time pushing the 2015.5 and 2017s up that high but I seem to remember the 5>6 comes a few hundred rpm earlier and the numbers don't climb quite as fast after that....and the bugs are harder to get off of the windshield

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    Now let me ask you, if i change the values in the part throttle shift normal table, do i have to make any modifications to the torque management and/or Torque Converter tables to accommodate the changes?

  14. #14
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    Any changes to shift scheduling need to be overlaid with torque converter scheduling to make sure they don't cause a complete freak-out. It just depends on what you want to do. If you like the general flow of things but want slightly later shifts it is a good idea to make sure the torque converter will fit within the schedule. This was not as important back when the converter was just applied in top gear but now that it is used between several of the lower gears it has to come and go at the right time.

    TM does not have to change with shift scheduling.

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    Thank you for answering my questions, I really appreciate it. Here is another difficult one: where are we supposed to enter the value of the transfer case for proper calculations for the 4WD low ? My first thought was under Speedo>calibration>Final Drive>low adjust. however the number entered there doesn't make any sense.

  16. #16
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    Sorry on the transfer case gearing. When I saw the question and other comments about it I looked at the files a little and did not reach a solid answer.

    I can tell you that 2015 L86 6 speed auto with 3.42 gear and NQH t-case has the same .73 for "low adjust" as a 2015.5 L86 8 speed with the 3.23 gear NQH tcase. So I expect that the .73 is directly related to the NQH low range ratio...I just have not figured out the math. Maybe somebody with some GEN5 4x4 files that don't use an NQH can help make sense of it.

    Please update that thread when you reach a conclusion. It will help a lot of us who are just starting to consider GEN5 4x4 swaps.

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    Will do.

    On another note, I was looking at the Part Throttle Shift - Upshift Normal Table. Is the Throttle Position Parameter in that table the same as the Throttle Position (SAE) value found on VCM scanner? If so, on my vehicle, it varies from 15% when the gas pedal is depressed to 84% at WOT. Why do they have 0 to 12 and 87 to 100 if you can never get there?

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  19. #19
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    Yes I did see that post, but it is pretty old (2006) and that specific PID (ETC %) is no longer present (at least not in my ECU/TCM).
    Also, the following PIDs are not linear: Absolute Throttle Position, Commanded Throttle Actuator, Throttle Position. They all start at 12%+ even when the gas pedal is free.
    The only relatable linear PID is Accelerator Pedal Position that actually goes from 0% to 99.6% as you depress the gas pedal (tested by yours truly). However, can this PID be used in lieu of the throttle position PID in order to adjust the Part Throttle Shift - Upshift Normal Table ?

  20. #20
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    Adjusting part throttle shifts is more art than science...as lots of cars take one setting into more consideration than another. I raise them a little at a time together and see how it goes.

    The PCM opens the throttle as much as it thinks it should for starting, idling, etc even if you are not touching the pedal. I cannot remember the specifics of why it is off at high throttle but that article seemed to be repeated for all 3 GENs.