my question of the day - downshifting

Discussion in 'Questions From New Drivers' started by LostBoy, Jun 7, 2007.

  1. LostBoy

    LostBoy Light Load Member

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    my school uses a simulator to attempt to teach you how to shift the truck before you get in the truck and dump a transmission all over the ground.

    set up as a 10 speed roadranger, they can program it to others, but thats what all of the school trucks are.

    when / how do i downshift this beast? the sims set to shift between 1500-2300 rpm's ish (wide range there) i can go 1-5, make the switch and go 6-10 like im driving a car. but as soon as i try to come back down, all hell breaks loose. i tried to double clutch, straight clutch like you would in a car, i end up letting the thing "roll to a stop" because i cant get it into any gear.
    the instructor said to go 300 up before shifting, 300 from what? 2300? wouldnt that make the engine reach back and smack you or atleast make the tach shoot out of the dash? shouldnt i being going down in rpms to counter the increase in resistance?

    we only have 15 minutes at a time to work on it so we dont get frustrated, but have to do an hour before we can get in the truck. i taught myself how to drive a standard fairly well in 30 minutes with no help, but that car only weighed about 2400 lbs.

    tips?
     
  2. goforce

    goforce Light Load Member

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    Normally if you downshift around 1000-1200 you will find that will work for you.

    Alan
     
  3. heyns57

    heyns57 Road Train Member

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    Learn the speed of the truck in each gear. Check the speedometer before downshifting. You may be traveling too fast for the gear you are trying to get into.
     
  4. heyns57

    heyns57 Road Train Member

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    the instructor said to go 300 up before shifting, 300 from what?

    300 rpm up from whatever rpm you had in the higher gear. Obviously, if you were wound out in the higher gear, you will have to slow the truck before you can downshift.
     
  5. munrkr

    munrkr Medium Load Member

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    Yeah, Goforce basically nailed it. When down shifting, let your rpm's come down to 1,000, then hit snap the acelerator to bring the revs up to around 1,500, then wait a split second for needle to start FALLING before taking the lower gear ( at app. 1,300). But remember, things such as weight of load, grade of road, and speed also effect shifting. But give that a shot and let us know how it works.
     
  6. notarps4me

    notarps4me Road Train Member

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    I been out of a truck for awhile, but seems to me that years ago (80's) the magic #'s were 19-21 in 2000 they were about 15-18 except for most macks I found around 9-13.
     
  7. attrintal

    attrintal Light Load Member

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    you have to increase the RPMs since downshifting uses a smaller gear, and thus motor speed needs to go faster to match the road speed. downshift around 1000 rpm. if you're going on a downgrade, and need to downshift, then do it around 800 rpm instead. never downshift going down a steep hill - because you can die that way
     
  8. enzogy

    enzogy Bobtail Member

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    The way I was taught is you slow the truck down to 1000 to 1300 rpm double clutch in neutral rev it up about 1400 to 1600 rpm to match truck speed and it should go in the gear.
     
  9. wallbanger

    wallbanger <strong>"Enemy of showers everywhere"</strong>

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    Basically correct except that you can be double clutching and revving up at the same time, and you will as you get more experienced (heck, you will actually start floating gears but that's another thread). But goforce is right.

    And if you miss a downshift going downhill, don't waste too much time trying to find a gear, grab a whole lotta brake and grab the shoulder. Then start over.
     
  10. beezle

    beezle Light Load Member

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    just got my cdl and what my instructor said was 1500 was the sweet spot upshifting you rev to about 2k clutch neutral clutch gear before it falls lower than 1500 so you do a count 1.. 2.. by the time you say 2 it should be in the next gear as for downshifting it has to do with speed but you clutch to neutral let off the clutch rev to just above 1500 clutch in and put it in the next lower gear remember dont bury the clutch to the clutch brake though otherwise it just wont work for ya i know in our trucks to go from 6th to 5th it had to be at 25mph or slower 4th is about 15 3rd is 10 and we only went into 2nd at a dead stop dunno if that helps but thats how we did it on a century class freightshaker with eaton 9spd
     
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