How does an autoshift work at slow speeds/dead load

Discussion in 'Trucks [ Eighteen Wheelers ]' started by someguy01, Dec 16, 2008.

  1. Dec 16, 2008 #1
    someguy01

    someguy01 Bobtail Member

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    How would an autoshift work with a really dead load at low speeds ?

    Lets say I had a truck with an auxiliary transmission and a 10 speed autoshift. Let say that I am climbing a steep hill or pulling dead load, like dragging the trailer through mud so that it doesn't roll well.

    Lets say with the aux box direct on the autoshift would be about 30 MPH.

    Will the autoshift shift correctly ? Or will the truck come to a stop between gears before it gets shifted ? Will the autoshift shift it really fast ?

    Thanks
     
    someguy01, Dec 16, 2008
    someguy01, Dec 16, 2008
    #1
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  3. Dec 16, 2008 #2
    Sportster2000

    Sportster2000 Road Train Member

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    This is a very good question. I do believe that the transmission will operate correctly. The transmission does not shift that fast so it probably will not shift very much. It will just stay in that gear longer to a higher rpm than it normally would. Now lets say you spin your tires and it tries to shift. The tires will slow down a lot during the shift. Causing the transmission to miss a shift and when it does this the engine will try to match the rpm to get into gear. When it does not do this on this try it will wait a few seconds and the go to full throttle. Why? I have no idea but that it what it is suppose to do. I personally have not had a transmission miss a shift, but several people I know make them do that on perpose.
     
    Sportster2000, Dec 16, 2008
    Sportster2000, Dec 16, 2008
    #2
  4. Dec 16, 2008 #3
    someguy01

    someguy01 Bobtail Member

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    Lets say we are shifting the transmission manually with the button and that we aren't spinning the tires. Lets say the engine RPM is well above the shift point, ie the computer wants to shift it.

    Will it miss the shift ? If it does, does it go back to the old gear ? What if the truck rolls to a stop in the mean time ?
     
    someguy01, Dec 16, 2008
    someguy01, Dec 16, 2008
    #3
  5. Dec 16, 2008 #4
    Captain Canuck

    Captain Canuck "Captain of the Ship"

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    Select manual mode and you will have no problems.
     
    Captain Canuck, Dec 16, 2008
    Captain Canuck, Dec 16, 2008
    #4
  7. Dec 16, 2008 #5
    Ken

    Ken Couch Commander

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    Mine will sometimes miss a shift going up a hill. It will either drop back into the gear it came from or it will go into neutral. What I do to get around this is put the selector into Manual. I'll take the RPMs a little higher and see if it will shift. If not I'll just climb in the lower gear until I know I can shift. I also make sure my jake is on, this will drop the rpm faster while maintaining my speed.
     
    Ken, Dec 16, 2008
    Ken, Dec 16, 2008
    #5
  8. Dec 16, 2008 #6
    C16KIWI

    C16KIWI Medium Load Member

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    We had a heavy haul expo over here last month and the demo truck was a Western Star with a C16,aux trans,auto shift,400k lbs rated.
    It was loaded with a 330 CL excavator (bush rigged) on a 4 rows of 4 transporter all up weight of 160k lbs it was taken out on some bush roads and stopped on steep tracks.
    It was unbeliveable how it moved and changed gears on such a grade sure did change my mind on auto-shifts.
     
    C16KIWI, Dec 16, 2008
    C16KIWI, Dec 16, 2008
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  9. Dec 16, 2008 #7
    someguy01

    someguy01 Bobtail Member

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    That is almost exactly the situation I was wondering about.

    How slow was the truck going and how steep was the hill ?

    Going up a hill, that is a pretty dead load, right ? The truck is going slow and it doesn't roll very far before it would stop. And it didn't miss any shifts ?

    Does it shift really fast ? Was it a 10 speed or an 18 speed ? Was it a generation II autoshift or the generation III ultra shifts ?
     
    someguy01, Dec 16, 2008
    someguy01, Dec 16, 2008
    #7
  10. Dec 16, 2008 #8
    C16KIWI

    C16KIWI Medium Load Member

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    It was on a off highway road on a grade of about 9% the aux box is just a 2 spd with that in low it shifted well taking the RPM up to 2100 seemed to shift fast as the road speed got better it shifted lower in the RPM.
    It never missed a gear it is on a 18sp not sure what generation it was also that was in full auto mode.
    It was pretty to watch,and all the old school heavy haul guys where amazed at how smooth it was.
     
    C16KIWI, Dec 16, 2008
    C16KIWI, Dec 16, 2008
    #8
    Big Duker Thanks this.
  11. Dec 16, 2008 #9
    C16KIWI

    C16KIWI Medium Load Member

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    I found the write up about it the local mag not sure how it will come out but I will try it.
     

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    C16KIWI, Dec 16, 2008
    C16KIWI, Dec 16, 2008
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  12. Dec 17, 2008 #10
    someguy01

    someguy01 Bobtail Member

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    Thanks guys.
     
    someguy01, Dec 17, 2008
    someguy01, Dec 17, 2008
    #10
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