264 Rear Axle Ratio???

Discussion in 'Trucks [ Eighteen Wheelers ]' started by whoopNride, Jan 26, 2013.

  1. sdaniel

    sdaniel Road Train Member

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    The Volvo Ishift and Mack's Mdrive with the 2.64 is a double over if I am not mistaken. Gets 65 mph to come in at 1150 on the tach. Heck sound just above high idle. Volvo is pushing it hard. And trying to get to switch over. Bought 40 of them , I think. Just not that ratio.
     
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  3. JarradS

    JarradS Light Load Member

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    not a double OD

    the I-shift is a single 0.78 OD like a 10 speed
     
  4. kwcat

    kwcat Bobtail Member

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    Hi Cowpie,I'm new to the truckers report and I respect your input.I'm running a 03 KW 900L C-16 18 spd 3.55 rears and 22.5 lp rears.I live in Cali so you know what I'm up against .Running at 55-60 the rpm is 1300-1350.Running at 65 puts my rpm up to 1450.I'm seriouly considering switching the rears to 264 so I can run in direct.My trailer in a 2007 maxlight with rolltarp system weighing 11,000.I dont care about drag racing .In LA traffic speed does'nt come into play.I'm going to add a nose cone to the trailer and some other aero tricks to the trailer to help with air drag.Just wanted your advice from someone who runs with 264's. I found a drivetrain shop in LA and they could only come up with 3.08's.I'll keep searching.Much thanks from kwcat.
     
  5. Cowpie1

    Cowpie1 Road Train Member

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    Yep, I am using the 18 with 2.64. I can pull everything I need to, everywhere I need to do it, just fine. Hardly anyone with the same gross weight can walk away from me on a pull. Now, 2.64 is not for everyone, every time. It does have some limitations, mostly in getting out of the hole at a traffic light change. It is not going to be as quick on the take off as, say, 3.58 or 3.70. But at running down the road, it does just fine. I pull a lot of 45k+ loads on some rural two lane, hilly stuff, and I have no problem. And running in direct drive is far more efficient, as the senior engineer from Eaton stated at the 2011 MATS. Now it is true, I have NEVER had my trans in the top gear, but if it was tied to something like 3.58, I wouldn't be using much on the low range either, so it is a wash. There is nothing written anywhere that states you HAVE to run in the top hole. I do use the bottom end a little more, but so what? I paid for the bottom just as much as I paid for the top! And the 18 has a real nice deep bottom granny gear to make up for any hard start issues on soft ground, mud, etc.

    If I was doing only 4 lane running, I could easily tip the 8 mpg mark frequently. But I have to pull some pretty hefty loads out of some rural areas a lot and run some hilly two lanes frequently, so my average is in the mid 7's year round.

    Now, don't overlook the 3.08! That is a good middle ground between the 3.58 and the 2.64. You would only be in the first overdrive, and that is way more efficient than in the top overdrive gear. If I wasn't running the 2.64, I would jump right on the 3.08 bandwagon. That would be an excellent choice. You wouldn't sacrifice a lot in start ability, and if you were in an area that you could step up the pace, you would always have the top gear to move up to and still keep the engine rpm's from hitting the roof.
     
  6. tator1960

    tator1960 Light Load Member

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    Dec 29, 2013
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    That was a tag axle setup for a while wasn't it? Running one diff and a tag to save on rotating mass weight.
     
  7. Grey Dodge

    Grey Dodge Light Load Member

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    There was a red 389 Pete done by PP That had a front lift axle on it.
     
  8. WitchingHour

    WitchingHour Road Train Member

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    With 11R22.5s and that direct drive transmission, he'd be running 68.5 MPH at 1500 RPMs... about where you'd be with 3.58s and a .74 OD trans with the same tires. Direct drive simply means that, in the final drive gear, the transmission input shaft turns at the same rate as the output shaft (as opposed to overdrive, where the output shaft turns faster than the input shaft). Running in overdrive does put a parasitic drain on the engine, but if you're trying to go up, say, Vail Pass, it's not really going to matter, since you're not going to stay in 10th gear, anyhow. Direct drive seems to be popular in Europe, where they have varied terrain and run 44 metric tons (about 97,000 lbs. and change). I wouldn't use it for sitework applications.

    Anyhow, at 1500 RPMs, you'd be looking at...
    71.6 MPH with 11R24.5s
    68.5 MPH with 11R22.5s
    68 MPH with 275/80R24.5s
    66 MPH with 275/80R22.5s
    And only 60 MPH with 255/70R22.5s.
     
    Cowpie1 Thanks this.
  9. dude6710

    dude6710 Road Train Member

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    How much of a difference is a .73 to a .74?
     
  10. Stone Express

    Stone Express Light Load Member

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    I love the look of 24.5 polished wheels. Is there a reason why a guy could not run 255/70s verses 1100 or 275/80s? I understand the truck would have to be geared accordingly, but it seems like that would drop a lot of rotating weight as the wheels weigh little, it is the rubber that adds up.

    275/80/24.5s with 2.64s would be about 1277 @ 60mph in direct. To run the 255/70s, one would have to go down to about 2.43s to run the same rpms, or with a 13 or an 18, one could run approximately 1205 rpms in the first OD.

    I understand one would give up some on the ride, with less sidewall to flex, but that would give the driver a backup to get the rig off the road to a shop with still having duals, verses running super singles. Should handle better too, plus more stability than singles.

    It would be interesting to see a roll down contest for drag between the two. Just conjecturing, I would think though that it would drop maybe 500 pounds on 18 tires. About half what singles do, or so the rumor is.

    Also, with the narrower tread, besides less rolling drag, there should be less wind resistance.

    Rotating mass is about 4 times as detrimental as pulling weight in the box, or so I have read.....
     
  11. Stone Express

    Stone Express Light Load Member

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    Feb 26, 2013
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    The difference between LP 22.5s with 3.55s running in OD, with either .74 or.73 is only about 17 rpms at 60. Not much.
     
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