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Thread: Reducing "agression" of cruise control on hills?

  1. #1
    Junior Member
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    Jul 2006
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    Default Reducing "agression" of cruise control on hills?

    This has always bugged me about my truck, but I'm not sure if it can be tuned out of it...

    When driving my truck in hilly areas with cruise control, i find it a bit too willing to grab 2nd gear in situations where it shouldn't. The scenario starts with the truck on a relatively shallow grade in 4th, at say 55mph/90kph The grade steepens, the truck begins to lose speed. The cruise increases throttle position, and the trans kicks down to 3rd. The truck begins to gain speed. The cruise continues ramping in throttle all the way up to 100% indicated TP, causing the trans to select 2nd. It goes PE (timer is zeroed), hits target speed almost instantly (it was already within 1mph) and drops it back in third, where it remains until the top of the hill.

    It's always done this, even when bone-stock (albeit it probably didn't go PE then).

    I don't see any parameters to cap TP% or adjust rate of change of TP% for cruise.

    I don't think D0907 (Part throttle 3->2 Shift Speeds) and D0961 (Throttle Kickdown, 3->2) are going to help. While both of those tables have cruise-specific settings, the cruise is commanding WOT which means open-loop instantly on my truck.

    Any suggestions on this, or might the above mentioned tables fix it (haven't actually tried changing them to correct it yet)? I really want cruise control to drive in a Grandma-approved fashion. Tired of explaining to passengers "no, that's the cruise control, it's !"

  2. #2
    Senior Member Wolfie's Avatar
    Join Date
    Dec 2007
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    182

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    I've been trying to eliminate that as well. I've tried changing all shift settings, even set the max etc opening to 99% and downshift to 100%, and even that didn't work. I could use a cure as well, especially when hauling 3000 lbs around...... sigh....
    Wolfie
    LS1B 2007 Express 6.0 /w 470,000+ miles (parked as of 01April2011)

  3. #3
    Lifetime Member
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    Mar 2006
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    My I6 does this too, aggravates the holy heck outta me but with a tune its more likely to not do it now. IE it makes more power so it can hold 4th gear longer and doesnt ramp TPS up so quickly so it stays in 3rd not 2nd.
    ~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.

  4. #4
    Junior Member
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    Apr 2007
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    Default

    Make the TC release more aggressive. Worked for me for several cars.

  5. #5
    Junior Member
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    Jul 2006
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    I think the part-throttle 3->2 may have helped it a bit. On closer inspection, it only hits 100% *after* it's in second. Not certain if it cures it all the time, but it's definitely better.

    D0961, "3->2 throttle kickdown" is now 100 for all cruise cells.
    For D0907 , I changed cells for 56.3% - 100% throttle. 56.3% is set to 45 KPH, 100% is 80 KPH. It's a linear progression between them, 5 KPH increase per cell.

    On my "test hill" I'm not getting 2nd anymore. That doesn't mean the problem is solved, but I think it may have improved.

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