The O/P plans of running standard 24.5 , with 3.36 gears and tall rubber . He will be very close to cowpies "final" drive ratio . Cow is running lopro 22.5 . With the higher rolling rest. it may be a tad worse ? Just one aspect appears to be over looked. Sni , walmart , usa , mavrick have all been using the 2.64 direct path several years . If its holding up under green horns at 80k . It should do well with us at our skill levels. Heck we ran 7 speeds , no back box robbing 3 to 5 percent of your hp . That was years ago on a ded gov run . Felt good getting over 10 mpg in 86 in one of these loaded at any weight !
Rear ratios
Discussion in 'Trucks [ Eighteen Wheelers ]' started by NFDDJS, Aug 24, 2012.
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What has to be understood is that once you are moving it is the overall ratio that determines grade ability.
Transmission ratio X Diff Ratio X tire revolutions per mile.
If you have enough gears with small enough steps you will have similar overall ratios available than with a slower rear set up.
You therefore will have no issues on a grade.
The downside is that on pull away or while backing under a trailer you wont have the very slow crawl that can be useful.
The upside is that you can run at cruising speed in direct drive in the transmission thus saving fuel due to less losses through the transmission.
When bob tailing or empty you can high idle at road speed saving a lot of fuel in overdrive.gator21 Thanks this. -
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I was looking at getting 3.58 rears before but now I am questioning if that would be to tall of a gear. I am looking to be able to run 70mph and be at a good over all RPM. With 3.58 rear ratio that will put me at 1500RPM when doing 72.3MPH and at 1400RPM I will be running 67.5MPH
I got this all from that site below. I just know how I drive and it is 5-8 mph over the speed limit most of the time 70% of the driving will be in 65 MPH areas and the other 30% in 55MPH and 35MPH areas.
I just feel that running 1400-1500 RPM most of the time with a C-15 is not going to be the best on fuel.
A ratio of 3.36 might be better putting me at 71.9MPH at 1400RPM
http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf -
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Cowpie, someday (hopefully a long time from now) some mechanic is going to tear that trans apart and say holy crap driver, you ever had this thing in the big hole?
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Two of my uncles have 2.64 and 10 speeds on the ex walmart trucks are great on fuel mileage but anything over 40k and you feel the stress that you're putting on the drivetrain we try to stay less than 30k on these trucks. We also have a t2000 with 3.36 13 speed c15 acert and super singles and even with XDN tires the truck struggles to start off in the snow because it always hauls very light loads. The rest of the trucks are either 3.55 or 3.70 and they're either single turbo c15, 3406e, c16, and the cabover with a big cam, all have 13 or 18 speed. In my opinion 3.55 is the best choice because we haul dry van, and once in a blue moon flat
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Dang. All this talk about 2.xx and 3.xx rear gears is making me sick. I've got 4.17's and if I changed 'em, I'd go to either a 4.35 or 4.42 ratio. I've driven trucks with 3.36 and 3.55 gears before, and they couldn't pull themselves up a hill...funny thing is, I got the same fuel mileage out of them as I do from my current rig....but my current rig drives a heck of a lot better.
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Right with you Pedigreed Bulldog. I have posted and argued many times before on this. I will burn alittle extra fuel anytime if it saves some wear and tear on drivetrain. Rarely under 80K and venture off road almost daily, the lower rear gears make a big difference. Always good knowing when i let the clutch out the truck is going to idle out of whatever hole it is in, without broken parts.
The_Great_Corn Thanks this.
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