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Thread: Desired Shift Times

  1. #1
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    Default Desired Shift Times

    How does the PCM compute the shift times for shifts?

    I set my desired shift times to 0.3s for all gears and logged the shift times. Average shift time was 0.12s for 1-2, 0.22s for 2-3, and 0.77s for 3-4.

    How long does it take for the trans to "adapt" to better hit these shift times?

    What does it adjust to better hit these shift times?

    It's a 4L80E with an HD2 shift kit. I've heard that with a shift kit it's harder for the trans to learn and adapt to the shifts, so many people recommend setting the desired shift times to zero.


    Log is attached.
    Attached Files Attached Files
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  2. #2
    Lifetime Member Chevy366's Avatar
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    With my Transgo kit I had to revert back to stock shift times otherwise it was way to harsh of a shift, of course I did "normal" on the hole size in the plate, I shot peened the holes and went back to "soft" hole size, still will shift with a good bump.
    If you zero them out it will bang hard and fast mine would chirp the rear from first to second, felt like someone was running into the rear of the truck.
    The kits are designed to enhance the stock trans with no adjustments needed, so keep it with stock shift times (actually all trans parameters), if you want harder/faster shifts use the holes in the plate (drill to largest size bit Transgo sent with the kit) to achieve that.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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    Quote Originally Posted by Chevy366 View Post
    With my Transgo kit I had to revert back to stock shift times otherwise it was way to harsh of a shift, of course I did "normal" on the hole size in the plate, I shot peened the holes and went back to "soft" hole size, still will shift with a good bump.
    If you zero them out it will bang hard and fast mine would chirp the rear from first to second, felt like someone was running into the rear of the truck.
    The kits are designed to enhance the stock trans with no adjustments needed, so keep it with stock shift times (actually all trans parameters), if you want harder/faster shifts use the holes in the plate (drill to largest size bit Transgo sent with the kit) to achieve that.
    Thanks for the info. I drilled all of mine to "average" I think. With stock tune settings the 1-2 is overly firm/jerky, not tire chirping though. And 2-3 and 3-4 feel like butter. Since I did the internal dual feed mod, I think I need to drill out the 2-3 hole a little more since there is now more space to fill in the direct.

    I'm having other issues as well, such as no TCC lockup unless my line pressure is over 150psi, then it will lock.

    I was just curious what "shift time" actually means. It does not appear to be the time from when the shift was commanded to when the RPM's drop.

    When I got from stock to zero desired shift times I don't really notice and change in shift firmness.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by ferocity02 View Post
    Thanks for the info. I drilled all of mine to "average" I think. With stock tune settings the 1-2 is overly firm/jerky, not tire chirping though. And 2-3 and 3-4 feel like butter. Since I did the internal dual feed mod, I think I need to drill out the 2-3 hole a little more since there is now more space to fill in the direct.

    I'm having other issues as well, such as no TCC lockup unless my line pressure is over 150psi, then it will lock.

    I was just curious what "shift time" actually means. It does not appear to be the time from when the shift was commanded to when the RPM's drop.

    When I got from stock to zero desired shift times I don't really notice and change in shift firmness.
    Here is a good read -- http://coloradofans.com/forums/67-te...explained.html
    It is for a 4L60E but it still applies.
    And here -- http://forum.efilive.com/showthread.php?1723-How-about-a-transmission-tuning-tutorial!&highlight=shift+time

    Did you do the kit yourself?
    Last edited by Chevy366; April 4th, 2014 at 06:12 AM.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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    I believe the Transgo HD2 changes TCC lockup into an On/Off style vs PWM, what are your TCC lockup % tables set to? Id set the low to 95% and high to 98-100%. See if that resolves your TCC lockup issue.

    The PCM will use the Desired shit time table as a target, if they arent matching that then you need to play with line pressures a bit (small adjustments, dont want to overwork the pump!). Id start by setting the trans settings back to 100% stock and see what happens.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Quote Originally Posted by Chevy366 View Post
    Here is a good read -- http://coloradofans.com/forums/67-te...explained.html
    It is for a 4L60E but it still applies.

    Did you do the kit yourself?
    Good link. Yes I built the trans myself.


    Quote Originally Posted by ScarabEpic22 View Post
    I believe the Transgo HD2 changes TCC lockup into an On/Off style vs PWM, what are your TCC lockup % tables set to? Id set the low to 95% and high to 98-100%. See if that resolves your TCC lockup issue.

    The PCM will use the Desired shit time table as a target, if they arent matching that then you need to play with line pressures a bit (small adjustments, dont want to overwork the pump!). Id start by setting the trans settings back to 100% stock and see what happens.
    I set the min PWM table to 90% and the max to 99%, didn't help the issue. If I manually ground the TCC solenoid at light throttle nothing happens. As I increase throttle, the line pressure rises and once it gets to about 150psi the TCC applies, but not quite fully, still slips several hundred RPMs. This morning I drove it with max line pressure which gives me about 180psi all the time and the TCC will engage and hold with zero slip.

    It's a strange issue, definitely needs to dig into the trans again.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  7. #7
    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by ScarabEpic22 View Post
    I believe the Transgo HD2 changes TCC lockup into an On/Off style vs PWM, what are your TCC lockup % tables set to? Id set the low to 95% and high to 98-100%. See if that resolves your TCC lockup issue.

    The PCM will use the Desired shit time table as a target, if they arent matching that then you need to play with line pressures a bit (small adjustments, dont want to overwork the pump!). Id start by setting the trans settings back to 100% stock and see what happens.
    Really Erik, didn't on mine.
    Don't go raising line pressures the Transgo kit should have done that for you if you installed the correct springs (until you figure out if something is wrong or not), a correct install of the Transgo kit will yield a faster firmer shift.
    Last edited by Chevy366; April 4th, 2014 at 07:55 AM.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

  8. #8
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    Quote Originally Posted by ferocity02 View Post
    Good link. Yes I built the trans myself.




    I set the min PWM table to 90% and the max to 99%, didn't help the issue. If I manually ground the TCC solenoid at light throttle nothing happens. As I increase throttle, the line pressure rises and once it gets to about 150psi the TCC applies, but not quite fully, still slips several hundred RPMs. This morning I drove it with max line pressure which gives me about 180psi all the time and the TCC will engage and hold with zero slip.

    It's a strange issue, definitely needs to dig into the trans again.
    How did the soft aluminum plugs fit into the plate holes they block off, I had one that was not to secure and had to make one that fit tighter. Might want to take a look at the plate again and make sure nothing has moved and that all springs are correct.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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    What plugs are you referring to?
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  10. #10
    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by ferocity02 View Post
    What plugs are you referring to?
    There are two small aluminum plugs that you insert into the steel section plate and hammer down flush to block off 2 passages.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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