Gear ratio over drive or direct for heavy haul up to 110K?

Discussion in 'Heavy Haul Trucking Forum' started by Nick34, Jan 12, 2019.

  1. Nick34

    Nick34 Light Load Member

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    Hey I'm in the process of specing out a new western star 5700xe with a DD15 engine and would like some real world experience with gear ratios. I pull a tri axle RGN mostly over size equipment around 70 000 to 110 000 pounds gross I was looking at going with 2 64 rear gears with a direct drive DT12 transmission but after doing some research some people are saying this ratio is only good for loads under 80 000 lbs because of startability problems from a dead stop with the taller first gear . The reason I wanted to go with the 2 64 was for fuel economy but should I go with the DT12 single over with 3 08 gears instead? the truck will have lp 22 .5 tires and I dont drive over 60. Any info would be great thanks
     
  2. x1Heavy

    x1Heavy Road Train Member

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    That's too tall. The 2.64 You would hate it. With that much weight against you will find that you burn up the fuel trying to get somewhere and not really doing very well.

    Anything higher than 3.2 should do you well. If you intend to be upwards of 110K gross you are better off with bigger gears IMHO upwards of 4's even. Otherwise the tiniest little uphill will cause you to fall down onto your hands and knees and not get anywhere.

    If it's overdrive you need, Im pretty sure you can find something even with that ratio.
     
  3. uncleal13

    uncleal13 Road Train Member

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  4. I glide 47

    I glide 47 Heavy Load Member

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    I run 264 and direct srartability not a problem but I never go over 80000
     
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  5. Humblepie

    Humblepie Road Train Member

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    Lol! Thanks for that laugh! I run a 7 axle. Regularly run 132,000 gross or more. Anything other than a 3.90 rear you won’t be happy with. The only caveat is if you are strictly flat ground in which case a 3.70 may do. Forget about fuel economy. When you are pushing all that wind you will want the grunt.
     
    Last edited: Jan 12, 2019
  6. 062

    062 Road Train Member

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    Wonder what he using now to pull that setup? Oh and you’re wrong cause KR said...
     
  7. Nick34

    Nick34 Light Load Member

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    Is yours an actual direct drive transmission or are you running an overdrive tranny in direct I was wondering if the first gear ratio might be Lower in a direct one to make up for the tall rear gear?
     
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  8. Humblepie

    Humblepie Road Train Member

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    I run a double over 18 and 4.30 rears.
     
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  9. Humblepie

    Humblepie Road Train Member

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    The thing you need to consider is not just weight. If you are pulling large crates or something the wind resistance can really make it pull hard
     
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  10. Rontonio

    Rontonio Road Train Member

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    I am going to try to be helpful,

    If you are moving RGN freight and are worried about fuel mileage as a primary concern in spec’ing a truck, you should re-evaluate your readiness to move forward. There is a reason people build trucks to do this type of work - they are set up to deal with issues general highway trucks are not. One is start ability and another is grade ability - so starting on an incline and maintaining traction on an incline both in pavement and off.

    Yes I know that 110k gross isn’t heavy but why build a truck that will suck at design weight and not be usable at heavier weights?

    I think the 5700 is absolutely the wrong choice for an RGN setup and I am a huge Western Star fan(I have one and have had more). You are going to need the ground clearance that the side skirts and aero pieces won’t allow or will get torn up. No one is impressed when a ragged out freight truck with panels cracked and duct taped shows up to load their half a million dollar injection molding machine.

    You should spend time talking to successful people doing the job you are trying to do. They are all probably running mainstream solutions (15l engines 1750/1850 500/550 with 13 or 18 spd transmissions with much deeper ratios like 3.7xor 3.9x and 46k rears long slide double locking fifth wheels full lockers etc)

    Western star has an engineering group that will offer solutions if you give them the information. Expected axle weights spacing number of axles terrain those kinds of parameters.

    Note: I do not have a bias against automatic transmissions but remember tow trucks for oversize loads are much more complicated(generally means more expensive) when things go wrong. When I looked into automatic- I looked at Allison. My application was very different than yours and it ended up not being the correct solution but maybe in my next truck.

    Lastly, money is made in the RGN world by skill, reliability and service. If you are going to get 5 mpg versus 7 mpg - you need to price your service accordingly, even as a 5 axle. If you are trying to make your money by cutting rates or accepting crappy rates - you are going to fail and hopefully fast so you don’t hurt a guy providing quality service.

    I have a friend that broke down with a big stretch load that we tried to help. Needed someone to go get the load and take it a long way through expensive permit states some requiring pilot cars. We would have done it - even just breaking even. When asked what he had in it - he said he only had x in it but it paid for his bounce. Problem is it didn’t cover the costs and now he either had to come out if his pocket farther or find someone who was willing to lose money too.

    I hope this helps
     
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