LSI Posted June 3, 2012 Share Posted June 3, 2012 having trouble with my archilles tendon on left heal.may have to spec with auto.Not sure wich way to go.I run about 62mph most of the time.Want to go with the 505hp.Like to get 7.5.60% of loads will be 35000. Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/ Share on other sites More sharing options...
slpwlker Posted June 3, 2012 Share Posted June 3, 2012 If I am not mistaken you'll have to gear it real high with a direct to keep the rpms down or get road speed. if you gear it alittle lower with the direct that will be a pulling sob. Gear it alittle lower say like 3.91 with an od or 3.55 to keep the rpms down. Where do you run the most. Gear it to run there. You pulling a van or Reefer? put a 13 or 14.6 front end in it with the tires to match and shorten the 5th wheel up as close as you can get it. Close the gap. I know Il will get you for 200 pounds over the steer. They are busting Groendykes but and making them get a mechanic out there to pull the fuel out to get light.Spec the little heavier axle and the tires and make them go look at the door tag.from a 12 to 14.6 there is not much difference maybe 1 spring. Friend of mine clsed the gap going from Maine to Oregon and gained if I remember right atleast 1 mpg which equates to big money Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122321 Share on other sites More sharing options...
LSI Posted June 3, 2012 Author Share Posted June 3, 2012 (edited) I'm pulling a dry van.My current truck has 13spd ,double od and 3:58's,ISX 525hp,1750ftlb/1850 on cruse,avg 6.3mpg,1350rpm's at 60mph..If I had to do over I would spec 3:70's.It has no power on hills,but could be egr and dpf problem.My old IH with 470DD,10spd direct,2:64's would pull Mt Eagle at 55 on cruse all day.Best I can get on this truck is 35 to 40 mph.Other day I followed a 455 Mack with auto in N.Dakota.Driver said he was getting 7.6mpg with 78000 gross.His truck was holding 65mph on all the hills and passing all the big CATS.Driver didn't know how his truck was spec'd. Edited June 3, 2012 by LSI Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122363 Share on other sites More sharing options...
slpwlker Posted June 3, 2012 Share Posted June 3, 2012 could split the difference. I got 4.11's with an 18od. now I'll cruise 55 to 58 sometimes 65 or better if I need to go. mind you I do oversize so there really is no comparision. I've been steadily getting 4.7 to 5.2 loaded. and 6 or better empty. Cut my idle as much as possible. this is all with a big Cat. been slowly putting more money in my pocket load after load from the fuel savings. Also taking it easy not putting alot of boost to the turbo and just taking time getting rolling. but same thing if I need to put it to the ground I do.Hope when I get back home to get the Gen put on the truck and will putting a roof top on probably before so it is already there when we get the gen. this may not sound like alot but topped off in Dallas, Wasn't super heavy or real wide but got 4.6 to Aurora,Co. got rolling 67 at one time keeping up with a buddy of mine. normally going out there I would of been in the low 3's or worse really putting it down Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122367 Share on other sites More sharing options...
Green Dash Posted June 4, 2012 Share Posted June 4, 2012 I don't know if this information also applies to the M-Drive, but here is an interesting article regarding gearing and engine speeds of a truck with Volvo's I-Drive.http://www.volvotrucks.com/trucks/na/en-us/news_and_events/news_releases/_layouts/CWP.Internet.VolvoCom/NewsItem.aspx?News.ItemId=109146 Quote Jim Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122405 Share on other sites More sharing options...
lucerne tractor Posted June 4, 2012 Share Posted June 4, 2012 The Mack garage in North Carolina had top notch mechanics. I was talking trade and all they could talk about was the M drive, for fuel milage, durability,pulling power, they all loved it and had no issues. It had a torque rating higher then an 18b, it was around 2050 to 2200? Gearing is alot differnt for the rears with the M drive I believe. High 3's mid low 4's? Mack know how to spec trucks for exactly what your doing. Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122410 Share on other sites More sharing options...
LSI Posted June 4, 2012 Author Share Posted June 4, 2012 The Mack garage in North Carolina had top notch mechanics. I was talking trade and all they could talk about was the M drive, for fuel milage, durability,pulling power, they all loved it and had no issues. It had a torque rating higher then an 18b, it was around 2050 to 2200? Gearing is alot differnt for the rears with the M drive I believe. High 3's mid low 4's? Mack know how to spec trucks for exactly what your doing. With the 3's sounds like it has OD. Quote Link to comment https://www.bigmacktrucks.com/topic/25444-m-drive-12spd-od-vs-direct/#findComment-122472 Share on other sites More sharing options...
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