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Thread: Tool to help tune A4 shift points...

  1. #41
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    Quote Originally Posted by joecar View Post
    I meant push the TCC release curve down further, for example look at 2002 Camaro A4 tune file, the 3rd TCC release and 4th TCC release are fairly flat down low... if your PCM keeps TCC applied on zero throttle, the having the 3rd/4th TCC release curves low keeps the TCC applied until car is going too slow for TCC, but while above this it feels like a manual tranmission, and makes engine growl when you release throttle (i.e. musclecar feel).
    Ok, pretty easy to do with 3rd release, and perhaps not so easy with 4th release in my case since the table is pretty squished together in my effort to make it more responsive. I did lower 4-3 a little, but as it currently stands there's no room to lower 4th release without going below 4-3. I've loaded the modified numbers into my PCM and am going for a test drive.
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  2. #42
    Joe (Moderator) joecar's Avatar
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    Since you have plenty of torque throughout the rpm range, you can push the 4->3 curve down lower...

    i.e. instead of easily downshifting at part throttle (and keeping rpm unnecessarily high), let engine torque do what it does best (pull vehicle along).

    ( one reason that the 4L60E survives behind an LS1 is that unnecessary downshifts (and subsequent upshifts) are avoided by having the downshift curves sufficiently separated from the upshift curves )


    ( in case you don't see it yet, automatic transmissions are optimized for drag racing, not road racing )

  3. #43
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    Thanks for coaching me up on this joecar! I spread out the 4th gear graph a little more and I think it's a good compromise between too responsive and lugging in high gear.

  4. #44
    Joe (Moderator) joecar's Avatar
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    Also: set the Throttle Kickdown tables to 100% TP all across, this allows the PT upshift/downshift tables and the WOT parameters to control shifting.

  5. #45
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    This thread is awesome!

    Gonna do some of these changes to my 4L80E swap and see how it behaves.

    Anyone done any for a 4L80E on a Silverado with stock tires? 3.42 gears and turbo

  6. #46
    Joe (Moderator) joecar's Avatar
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    This is a key point...

    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.

  7. #47
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    Quote Originally Posted by joecar View Post
    This is a key point...
    Don't forget about TCC lockup. I bring in 4th lockup a lot sooner than stock and I have an area around 40-45mph where the truck locks in 3rd, shifts to 4th, unlocks, then realizes it should be locked. All without moving my foot. It doesn't happen very often, so I constantly forget to look at it on the tune. 4th should come in sooner than 3rd lockup and I'm pretty sure that's what I command, but they may be a little too close together. Don't forget about downshifts, mine is programmed to hold 4th lockup with quite a bit of pedal. If you go too far, you'll downshift straight to 2nd and never even think about 3rd or they'll be so close together the vehicle may hunt between the 2. All stuff I've encountered while playing with the trans shift points.
    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.

  8. #48
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    Well I started fooling around with a table and then decided to drive around a bit with the stock 2009 G3500 4L80E tune shift points so I can actually feel where I want improvements. The stock 4L60E shift points are actually much higher and "sportier" ... also the tow/haul works very different and holds 4th until a pretty high speed vs. The stock 4L60E tune. I may just keep that as is.
    For now, I'm assuming, as it's a Van (not a sports car/truck) it has pretty low shift points and tcc lockup tables. Also these shift points seem to be optimized for a 4.10 gear ratio than my 3.42 ... so I feel I'm spending a lot of time with the engine well below the power band with no power and lots of turbo lag. I could in essence increase the tcc tables so around town driving isn't as luggy with the tcc locked up but feel it's a bandaid to the bigger issue of the gearing paired to my 4L80E ratios. May start looking into a 3.73 or 4.10 soon.

    Sent from my SAMSUNG-SM-G900A using Tapatalk

  9. #49
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    can someone look at this? I copied the 4L60E shift points in (they're a bit higher) and then adjusted the downshift curves to not intersect any other curves, then played with the TCC curves.

    Thanks!
    Attached Files Attached Files

  10. #50
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    Quote Originally Posted by Supercharged111 View Post
    Don't forget about TCC lockup. I bring in 4th lockup a lot sooner than stock and I have an area around 40-45mph where the truck locks in 3rd, shifts to 4th, unlocks, then realizes it should be locked. All without moving my foot. It doesn't happen very often, so I constantly forget to look at it on the tune. 4th should come in sooner than 3rd lockup and I'm pretty sure that's what I command, but they may be a little too close together. Don't forget about downshifts, mine is programmed to hold 4th lockup with quite a bit of pedal. If you go too far, you'll downshift straight to 2nd and never even think about 3rd or they'll be so close together the vehicle may hunt between the 2. All stuff I've encountered while playing with the trans shift points.
    don't 4L80E's unock TCC for shifts? I've seen that in my logs. It'll go 1>2>3>LOCK>UNLOCK>4>LOCK ... annoying

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