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Thread: Upshifts Too Late, Downshifts Too Soon In One Truck But Works Great In Another

  1. #11
    Joe (Moderator) joecar's Avatar
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    The other problem is that your PT shift tables cross (in four places)... they should not cross anywhere, see attached graph:

    Click image for larger version. 

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    At any TPS % value, the order of the shift table should be as follows
    (from top to bottom as you look at them stacked onto the same graph):
    3->4
    4->3
    2->3

    3->2
    1->2
    2->1


    Do the same with WOT shift points.


    Quote Originally Posted by joecar View Post
    PT shift table relationships:

    basic relationships:
    1->2 curve should be above 2->1 curve;
    2->3 curve should be above 3->2 curve;
    3->4 curve should be above 4->3 curve;

    additional relationships:
    3->2 curve should be above 1->2 curve;
    4->3 curve should be above 2->3 curve;

    this can be summarized as: the curves cannot cross anywhere;

    if they cross anywhere, then you will not be able to predict what gear the PCM selects when the operating point hits the cross.

    A4 shift table spreadsheet is here.
    Last edited by joecar; March 16th, 2018 at 06:50 AM.

  2. #12
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    The shifts were not this harsh before the TB swap and I'm commanding some quick shift times in the 1500 and it doesn't slam the way this one is. It really feels like something has faulted and driven the line pressure up, it even hits when shifting from park/neutral to gear. Now I did modify my TPS to be adjustable and set it so it'd read 0 at idle and figured that was good enough, but the throttle keeps on going a decent ways past 100%. I ASSume this is normal as I hooked up other throttle bodies and witnessed them do the same thing. The truck does have a P0122 since the TB swap which is TPS circuit low but every time I'm looking at TPS while logging it seems normal? That said, it is now being weird about shifting out of 1st and 2nd at low speed, give it some lovin and it upshifts. I'm not sure what to make of it because my log from last night doesn't seem to show any breaks in TPS data?

    Dually Log 10 After TB Success FINALLY.efi

    You'll need to forgive last night's optimism in naming my log, it was clearly unwarranted.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #13
    Joe (Moderator) joecar's Avatar
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    No worries, stuff happens.


    It sounds like you need to reset/relearn the TPS voltage.


    Log the pid GM.TFMPRS and see what pressure the PCM is commanding.

    Take a look at the current DTC's in your log... then in your tune under the Transmission Diagnostics section, try to find those DTC's in each of the fault tables see if they are enabled... if they are, disable them and test drive.


    Post your current tune file.

  4. #14
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    Quote Originally Posted by Supercharged111 View Post
    The shifts were not this harsh before the TB swap and I'm commanding some quick shift times in the 1500 and it doesn't slam the way this one is.
    Shift times does not cause the hit... lack of torque reduction is what does it. Put some torque reduction back in and make the shift times a bit longer... 0.35 for 1-2 and 0.4 for 2-3 and 3-4. Don't be tempted to reduce line pressures... you'll just burn up your clutch packs.

  5. #15
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    I'm scared shitless to touch line pressure, even to bump it to lessen the adaptive correction factor when shorter than stock shifts are commanded (I ASSume that's how you're supposed to do it?). I am thinking I ought to rip off some of the trans stuff from an 8.1 4L80E Avalanche or Suburban though, all this trans stuff right now is based on the 5.7 4L80E in the Express van. Shift times have all been put back to stock for a 454 4L80E 1 ton pickup and they're not much if any different feeling than when I was commanding the shorter times. The log for GM.TFMPRS was parked at 90 psi for the entire drive. My DTCs are as follows:

    P0122 - Throttle Position Sensor 1 Circuit Low (C)
    P0405 - EGR Position Sensor A Low Voltage (C)
    P0463 - Fuel Level Sensor 1 Circuit High Voltage (C)
    P1122 - Throttle Position Sensor Intermittent Low Voltage (H X S)
    P1637 - Generator 2 L Terminal Circuit (C), Not Used
    P1638 - Generator F Terminal Circuit (C), Not Used
    P1665 - Engine Oil Pressure Output Circuit (C)

    I did a search and it looks like I need TPS voltage to be .5-.6V at an idle, then reflash to get it to learn? I imagine that ought to fix the P0122 which I was so sure would be a trans pressure enabler/modifier, but it was already set to no in both. P1122 wasn't in there at all (though since it isn't current, I assume it simply wouldn't be a factor). EGR is disabled in the tune, is it then appropriate to not only disable MIL but also processing enablers? Would that prevent it from coming up in the scanner when I pull codes? Also, since my truck is a 97, the PCM does not have its mitts in the fuel gauge or the alternator output. P1665 comes as a surprise, going to have to investigate that. P1122 really implies I went too far to get the TPS to read zero, it seems a relearn is in order before I rip my hair out over nothing. Is the relearn as simple as I found above?

    Log_0005.efi
    Dually Attempt #16 Shift Times and Kickdown Delete.tun

    I didn't deconflict the shift points yet, trying to get this right first as its affecting low speed shifting. If feels like there's a dead zone where the PCM doesn't see throttle input, but the logs seem to imply otherwise.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  6. #16
    Joe (Moderator) joecar's Avatar
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    Supercharged111,

    make sure to understand what statesman said:

    Quote Originally Posted by statesman View Post
    Shift times does not cause the hit... lack of torque reduction is what does it.
    Quote Originally Posted by stateman
    Don't be tempted to reduce line pressures... you'll just burn up your clutch packs.
    you can add Torque Reduction back in to soften the shifts (TR injects momentary spark timing reduction during each shift).

  7. #17
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Supercharged111 View Post
    ...
    The log for GM.TFMPRS was parked at 90 psi for the entire drive.
    This would explain hard shifts at low/moderate part throttle... we have to find out what is causing TFMPRS to be 90 psi always (max is 96 psi).


    My DTCs are as follows:

    P0122 - Throttle Position Sensor 1 Circuit Low (C)
    P0405 - EGR Position Sensor A Low Voltage (C)
    P0463 - Fuel Level Sensor 1 Circuit High Voltage (C)
    P1122 - Throttle Position Sensor Intermittent Low Voltage (H X S)
    P1637 - Generator 2 L Terminal Circuit (C), Not Used
    P1638 - Generator F Terminal Circuit (C), Not Used
    P1665 - Engine Oil Pressure Output Circuit (C)
    Those DTC's are enabled in the Trans Diag tables E010x... we have to see which of those DTC's are present, and fix the base cause.

    I did a search and it looks like I need TPS voltage to be .5-.6V at an idle, then reflash to get it to learn?
    You can get it to relearn idle voltage by disconnecting TPS, powering up PCM for say 10 seconds, then powering off, reconnecting TPS, and powering up again.

    I imagine that ought to fix the P0122 which I was so sure would be a trans pressure enabler/modifier, but it was already set to no in both. P1122 wasn't in there at all (though since it isn't current, I assume it simply wouldn't be a factor). EGR is disabled in the tune, is it then appropriate to not only disable MIL but also processing enablers? Would that prevent it from coming up in the scanner when I pull codes?
    TPS problem has to be fixed regardless.

    If the DTC is disabled, you can leave the MIL on (since the DTC will not trigger).

    Also, since my truck is a 97, the PCM does not have its mitts in the fuel gauge or the alternator output. P1665 comes as a surprise, going to have to investigate that. P1122 really implies I went too far to get the TPS to read zero, it seems a relearn is in order before I rip my hair out over nothing. Is the relearn as simple as I found above?

    Log_0005.efi
    Dually Attempt #16 Shift Times and Kickdown Delete.tun

    I didn't deconflict the shift points yet, trying to get this right first as its affecting low speed shifting. If feels like there's a dead zone where the PCM doesn't see throttle input, but the logs seem to imply otherwise.
    Do you have a wiring diagram for your specific vehicle, to see if PCM is involved in alternator and/or fuel gauge...?

  8. #18
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    Quote Originally Posted by joecar View Post
    This would explain hard shifts at low/moderate part throttle... we have to find out what is causing TFMPRS to be 90 psi always (max is 96 psi).



    Those DTC's are enabled in the Trans Diag tables E010x... we have to see which of those DTC's are present, and fix the base cause.


    You can get it to relearn idle voltage by disconnecting TPS, powering up PCM for say 10 seconds, then powering off, reconnecting TPS, and powering up again.

    TPS problem has to be fixed regardless.

    If the DTC is disabled, you can leave the MIL on (since the DTC will not trigger).


    Do you have a wiring diagram for your specific vehicle, to see if PCM is involved in alternator and/or fuel gauge...?
    Alright, looks like a TPS relearn with the initial TB install would have been the ticket. I was getting around .24V at idle with the reclocked TPS and could only muster .4X V spun back to stock, so I installed an unmolested sensor and it was sitting at .55V with the idle stop as I set it. Since there's so much to be tweaked, I killed the MIL and some enablers for stuff I don't care about, bumped TCC lock to 100% min/max, and went for a spin (not harsh at all, shouldn't come as a surprise since the 700R4 was on/off as well). TFMPRS was much lower initially and reacted with throttle, shifts felt stock as they should.

    To be clear, I wasn't blowing off what Statesman had said about TR, but the fact is I had left all the stock TR intact on the upshifts and haven't touched it on any iteration of tune on this truck. I'm pretty sure I left it all in the 1500 as well, just seems to make sense to me. I can go back to those shortened shift times I'd posted before as they were anything but harsh.

    I have a nasty habit of only posting for help on here when I'm nuclear which usually happens when I've tried fixing something for the 10th failed time or I'm about to bust a deadline of some sort for needing a function I seek (like trailer pulling ability in OD to pick up a car from paint). So the cause of crappy throttle response was a progressive linkage and the cause of the bang shifts was me not doing a TPS relearn. Since this all came about during the TB install, my suspicion was something physical rather than tune related, but man did that response thing piss me off. Now I can focus on deconflicting shift points, correcting idle airflow, and seeing why my timing seems capped. I really didn't want to end up trying to tune around something and then have to turn around and undo it all. I did that with the blue truck when I was running speed density and didn't get very far. Only code to come back on the drive was the 1665 oil pressure thing, going to have to have a peek at the pinout and see what's going on with that. No need for a wiring diagram, 97 was the last year the PCM was not involved with the fuel gauge or alternator. 98-00 black box PCMs like that on my 1500 were involved. The fuel pump and sending unit/basket were changed, fuel gauge began to receive a PWM signal from PCM, and the PCM began to command alternator current. They also got the next gen airbag and a different stereo among other things I'm sure. My dually is nice and dumb.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  9. #19
    Joe (Moderator) joecar's Avatar
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    Do the upshifts have a firm feel (firm meaning not hard, but positive and definite)...?

  10. #20
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    When shift times are shortened yes, they were more firm and not harsh at all. The 1500 has a shift kit and hits hard enough to break loose in the rain on 1-2, but again nobang like I had with the dually. Just a huge shove in the backside, feels like a slingshot more than anyhing. Dually doesn't get that spicy without the shift kit.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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