This message is for COWPIE1 or anybody else with info regarding a GLIDER TRUCK..=)

I'd get the 18 speed. You do not need it now, but maybe your needs might change two years down he road. Having the 18 speed won't hurt ya, as for final drive ratio, that's a whole different argument . I'll be following this thread to see what some of the more experienced guys have to say about that one.

 

Final drive gear ratio is only part of the story. Tranny type is also a partial information. Tranny gearing, final drive gearing, engine power curve all contribute to an optimum solution. Then too, what about idle time, shift points, and other driver impacts? That roadranger site looks useful.

 

What you have is good. Work on getting it dialed in, tuned, checked out by a good shop. Your current set-up should give you a good mpg.

 

There are no dumb questions only dumb answers, don't be afraid to ask your dealer what you need to know!

HP vs Torque! Power is rated by torqure/ft/lbs rpm. Most commercial highway engines produce 1900 to 2100 ftlbs at 1300 to 1500 rpm when correctly tuned ie cummins 550 hp 15 liter or DD15. HP rating is related to speed, study and learn the difference between power and speed as it relates to engine performance.

FL vs Pete or KW? An '13 Pete 386 has everything. Aero-dyamics, gears ratio and higher fuel economy (than a 379 long nose pulling 40K in the box). the newer trucks can get 8 miles per gallon ave in Texas and Louisiana when properly driven. The fuel cost is determined by many factors, idle time and driving habits (progressive shifting).

Why worry about saving 3 cent a gallon at the pump when your spending $3.00 dollars an hour to idle? APU???? As a profit driven business operator keeping expenses under control and maintaining a budget is key to being successful.

 

What about keeping what you have for a while & ask rebel, what he could do for your engine, m.p.g. & performance. with the right deletes & tune, you could gain enough m.p.g. to save an extra $600- $1000 a month.

 

A 14 litre Detroit should pull well. As others have said , get it checked out. It seems that poor fuel economy is often related to a problem with the egr system. I have a friend with the same set up you have. His fuel economy was down to 5.5 mpg at 65 mph. He went to a freightliner dealer and they made some kind of adjustment ( egr, turbo, not sure exactly). His fuel mileage then went up to 6.5 mpg. Also, try running slower, like 60-65 mph. That should improve your fuel mileage.

Also, another friend had his computer reprogrammed. It deleted his egr on his Detroit. He said it pulls really well and get 6.5 and better on fuel mileage.

 

I agree. That 515 Detroit and the 3:42s should work as well as anything on the market. Is she getting alot of blowby? Is she smoking out the exhaust?

Is the truck an old fleet truck? If so, I would suspect that she's running the old beancounter ECM tune where they'd cut a factory 515 HP down to around 430 HP or less. Calling a cut back truck "sickly" is an understatement. Fuel economy is nil, and wont pull for squat.

515 HP, healthy, should be overkill for Texas and Lousiana.

 

Yes. There are some nice pulls out in east Texas. Every time I pull a hill, even empty, my OH #### light comes on.haha

 

I agree. I think an 18 speed would be too much for what I do.

 

I have already replaced the ECM, EGR, turbo, 3 piece manifold, injectors, ect.. There is nothing wrong with my truck from what the dealer says. I had the EGR bypassed for a while, and it started to pull a little bit better and got better fuel mileage but that didn't last very long till the computer noticed what I was doing.lol