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Can I run a 10spd over drive with 2:79 gears?

I have a 2003 freightliner, with series 60 Detroit, and an Eaton Fuller (FRO-16210C) transmission. I think 9th gear is direct and 10th is the overdrive. If I gear this truck with 2:79 rears can I run this transmission like a 9 speed direct, using 9th as my top gear? Can anyone verify this transmission and let me know if this set up could work. Will I have enough start ability with this setup? Thanks for the help.

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Ok. I run a Eaton 18 speed in front of 2.64. I run in 16th (direct). My trans stays considerably cooler than either lower or higher gears. I have been using this setup for 2.5 years with no problems. But then, the 18 has very deep bottom end reduction compared to a typical 10 OD and 13. Start ability problems are very rare, and I haul a lot of 46K loads in the box. If a person is running lighter, start off problems will be minimal, so a 10 would work fine. If there are situations where heavy and starting off on any incline, you will not be a happy camper.

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ok, thanks for the info. I run 50% at 80,000 and 50% at 26,000. Tanker work. Right now I'm using a 10spd direct with 2:79 ISM Cummins 370hp, single rear axle with forward liftable axle and it works pretty good. Fuel mileage is around 9mpg. The truck I'm building has 3:73 10spd overdrive series 60 detroit 425hp. I wanted to go to 2:79 run in direct. What do you think? Thanks Cliff

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The 10OD does not have the same deep reduction in the bottom as a 10 direct. If you do not ever have hard start offs on inclines and other similar things, it could work. Get out charts from Eaton and compare the 10 direct gear ratios to the 10 OD ratios. Look at the spreads. It just might be a viable option.

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I do not believe you will have any start ability problems and direct is the same in all transmissions. Does this trans have a cooler? If not I would recommend on because it will run hotter in direct than overdrive. Why such tall rear ends?

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I'm building a truck just for fuel mileage. I want to run 55-58mph in direct drive. 2:79 is the rears you use for that. When running in overdrive you actually create more heat than in direct. When your in an overdrive gear there is actually a mechanical disadvantage. This is why overdrives are 3-4% less fuel efficient than direct drive transmissions. Also many direct drive transmissions do not have coolers on them for the simple fact that they run cooler in direct.

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May be different for you but I have a RTLO 18913A and it always runs hotter in direct than overdrive. It did it before I had it built and it does it now.

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I am running a 2.64 gear with a 16610B super10,first gear is 11.06,i only have starting issues on steep inclines when loaded heavy.first gear in an average 13 will be 12.31 or 12.56. I did it this way only because tranny still works and im cheap,not replacing until i need to,then will go to a 13,but thats mainly so if i need to run a little harder first od in a 13 will be .86 vers it s the .74 or.75 od of the 10 spd

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Rick will be eternally grateful.
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