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Thread: How to prevent down shifting when towing

  1. 02-07-2006 #1
    stan
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    How to prevent down shifting when towing

    I am trying to keep the trans in the gear I select either 3rd or 4th (if there's no wind) when towing my enclosed car trailer with a 6.0 and 4L80. I set the top few throttle % speeds on the 3->2 shift to 60 and the top 5 throttle % speeds on the 4->3 shift to 65 in the part throttle performance table. I also set the WOT shift speeds to 60 and 65 for downshifting. At 70 MPH in tow haul mode it still downshifts near WOT. I also set the TCC apply release table numbers near WOT to be 60 for 3rd and 65 for 4th in performance mode. The convertor still releases in tow haul mode. The release TPS charts are all filled in to 100 %. Any ideas?? thanks Stan
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  2. 02-07-2006 #2
    jimmyblue
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    You may find it helpful to make an Excel display sheet like
    these, to visualize the lock-above, unlock-below points on
    a TPS rather tham MPH basis. You need to have some
    TPS margin above normal, light-grade tow level to not
    unlock. Meaning that, where you operate, the unlock
    MPH (unlock below) and lock MPH both need to be lower
    at that recorded TPS.
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  3. 02-07-2006 #3
    12secSS
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    In order to make those changes viable while using the Tow/Haul mode, you need to modify the Performance Shift Tables ... as that is what the trucks use when the Tow/Haul button is activated. Hope this helps.
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  4. 02-07-2006 #4
    stan
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    Attached are the files I modified. I was using the performance tables. What am I missing??
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  5. 02-08-2006 #5
    jimmyblue
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    What is your range of observed TPS% when hauling? How
    much do you want to push the pedal before you unlock?
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  6. 02-08-2006 #6
    stan
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    Haven't pulled my trailer since I got HP Tuner but it takes almost full throttle to top some of hills I go over weighing almost 15,000 lbs total. 90% would cover most hills but I wanted to just downshift manually if I needed to and not have it downshift all the time just before I top a hill.
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  7. 02-08-2006 #7
    jimmyblue
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    Sounds like you want to set your TCC lock
    MPH to the bottom of gear (like, copy your
    upshift 2-3 MPH vs TPS row to the 3rd gear
    TCC lock MPH vs TPS) and then set the unlock
    even lower. This basically says, lock it always.


    Do that to the Performance tables and try it
    out. Same for 4th gear though I kind of doubt
    you're towing in OD?
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