mercer transportation

5.4 is still low. I've strive for close to 8.
Speed can make alot of difference. Gear ratio vs rpm can also make a big difference. Most trucks need to run at or under 1400 rpm to get best mpg.

 

I added an apu, 2 years ago in jan 2012, I gained 1mpg by simply cutting out idling. then I began an effort to simply slow down, take more time getting up to speed and running at a slower speed. I basically run 60 t0 62 all the time. at 62 in 13th I am dead on 1300 rpm.

I also try to find light loads with good rate the best I can, like now I got on 5,000 pounds @ 2.16 a mile to truck, 850 mile run, then I got to reload a 1100 mile run with 8,000 pounds at 1.95 a mile. on top of this I rigged up my front trailer axle to lift up . that helps tremendously also.


I am at a 7 mpg gallon also with a c-15 2006 t-600. I have looked at flightline's truck. the guy should open a shop, he has customized items made by himself that are amazing. but several things he has fabricated himself wont be found on the average big house.

I wish I had the drive to do the things he has done to his truck.

 

Well my truck is not geared the way I thought it was. With the gps now actual speed of 65 the engine is turning just shy of 1600 rpm. To keep it at 1450 I'm only going about 58mph. i got a pretty light load now at 3400lbs.

 

what tranny have you bad monkey?

 

10 speed eaton. Not shure if it is direct or overdrive.

 

Rob, if your Speedo is off, there is a good chance your tach also is. A good shop should only take half an hour to calibrate them, would be worth the hour rate imo. Get that cac pressure checked while in there. They would also be able to tell you exactly what your gear radio is. Or you might be able to find that with a Google search for the math formula. Once you get your ratio figured out, you can make an educated decision of what to do next. It might be changing tire size or it might be changing your rear ends. Basically the idea is to match everything up so that you can run at x speed while turning y rpm. The rpm is decided by what engine you have. The speed is set by you alone, how slow can you run before you eat a bullet. I am at the 60 to 62 range and drop down to 58 on really light loads

 

Need to get under your truck and find the identification plate on that tranny. The rear ends also have one but if the previous owner ever switched out gears he may not have put a new id plate on it. As I said before there is a formula to figure them out, gotta Jack the truck up and measure how far that wheel end spins over when you turn the drive shaft over.

 

Wow.
1600 rpm's is killing your fuel economy.
I'd find a way of changing that or drive 58mph.
Apparently your rear end ratio is wrong for that trans. unless you only want to run 55mph.
Your rearend ratio is probably around 3:90. If you could find a single screw of 3:55 and a lift axle, then your fuel economy would go up dramatically.
Othwise might consider trading trucks and if you go that route, look at the rmp's when you test drive the truck. There is alot of trucks set up with the wrong ratio's for economy.
Another option might be to change the trans. out with a 13 speed overdrive. (Though I'm not sure this would be enough or the right direction)

 

opps. double post

 

I'm not sure you can physically turn the drive shaft. You jack up one wheel, mark the drive shaft, spin the wheel one full revelotion and count how many times the driveshaft turns. I will normally be 3 and so much. The so much is like .9 or .55 . I have seen 4.11 and your big dump trucks have up into the 5.35's