This shows promise

[LSI]

GATR Mack in Cedar Rapids Ia has a Pinnacle with 455hp,12spd M-drive single o.d.with 2:64's.This looks like good gear selection for running 62 to 65 mph with hills and flat ground.whats your opinion?

you would have 11 gears to run direct and 1 o.d. for running lite or mt.Maybe go with 2:50's.

[Dirtymilkman]

That is the super econodyne? Those pull real nice at 1100 rpm!

[LSI]

That is the super econodyne? Those pull real nice at 1100 rpm!

I think so

[LSI]

I think so

Dealer said it was 455hp SE

[Green Dash]

Our M-drive is a direct with 2.64 rears and runs 65 mph at a hair over 1400 rpm, the od will have you doing that at 1100. My understanding is that the od will be used on flat ground, even when loaded, and immediately downshift at the slightest upgrade. Sounds like you'll get some impressive mpg numbers even if much of your day is spent in direct.

[Vladislav]

Looks to me as a space-travelling combinatoin.

I still think on to change the rears to 4.64's or 4.17's having E6-350 with 0.8OD box or to stay as is with 5.02's.

It does now 60 with no trouble having 11.00R20's at rear wich will be changed to 11.00R24.5's.

[Dirtymilkman]

I was taught in schooling that you'll get better economy with a direct transmission and very high rear ends. With overdrive gearing in a transmission there is more drag because of gear sizing. Coefficient of friction I believe the term was?

[RowdyRebel]

I cringe whenever I see a 2.xx gear ratio. Might work in a highway application, but it just doesn't seem like it would get the job done if the directions to the shipper or receiver ever included the phrase "turn off the paved road". All that fuel money saved going down the road will be paid out again 10x over fixing what gets tore up at the job sites.

[LSI]

I cringe whenever I see a 2.xx gear ratio. Might work in a highway application, but it just doesn't seem like it would get the job done if the directions to the shipper or receiver ever included the phrase "turn off the paved road". All that fuel money saved going down the road will be paid out again 10x over fixing what gets tore up at the job sites.

I had an International cabover,1999 with 470 Detroit,10 speed direct.Yearly avg fuel was 6.8 hauling 79000.It would pull Mt Eagle in top hole and maybe drop 1 gear if I forgot to wind it up at the start of hill.

[farmer52]

I was taught in schooling that you'll get better economy with a direct transmission and very high rear ends. With overdrive gearing in a transmission there is more drag because of gear sizing. Coefficient of friction I believe the term was?

True, 1:1 is a direct straight thru without any gears or loss. Overdrive uses a gear set (drive loss) to obtain a 0.73 or ??? ratio (potentially more wear on gears and bearings). I also agree, you need to run a fast axle ratio (low number) but it does not work very well in hills or off-road. I have a friend who managed a mid-Western fleet and ran 10speed directs because he achieved better fuel mileage

[mack mhe9]

Yes in direct you're not spinning the counter shafts, that's why they run direct on a dyno. I would prefer a 13. Or 18spd closer gear setting so you hit a hill just spilt the gear and your on top of your power. As for grade ability if your running on mild grades 90% of the time the the fuel savings will out way down shifting in the hills.

100.000 miles at 6.5 mpg 15,384 gal. And at 3.80 per gal. That's 58.459 dollars

100.000. 7.5 mpg 13.333. 3.80. 50.666

So that 8 thousand a year. Plus fuel taxes are going up so what little you can save I would do.

Sorry about the rant.