It's been a long time since they've built a 13 with a direct main box and overdrive auxiliary. Most guys doing 2.64 rears put an 18 in front of them to have decent startibility, and 16th is direct (11th in a 13)
Detroit DD13 vs DD15 for 80,000 lbs: Fuel Economy, Power, and Maintenance Costs
That’s not the case. Nobody near me has one on the lot.
ironpony
Professional Pot-Stirrer
You specified operating at 80k gross. DD13 will get you over the hill. The larger motor - DD15, is more driveable, and will get you over the hill first. I have an '09 which is out performed by newer DD15s. I still have not seen a DD13 comparably loaded, that will out perform my truck.
Gonna get a DD13? Make sure its Radiant Fire.
Gonna get a DD13? Make sure its Radiant Fire.
I get the power thing, and it is part of my decision. It's not my entire decision, however. I will happily let somebody get to the top of the hill before me, if I am getting a consistent MPG improvement with a smaller engine. I've stated before, I climb hills currently in a gear lower than what I could climb and typically operate at 75% throttle up the hill.
Whether I go DD13 or DD15, if I go forward with a new truck purchase, it would be a downsped setup, so neither would be reaching the power levels of a wide open 500hp DD15.
As for hills, I would be more concerned with how well the truck is going to go down the hill. I would have to factor in a stronger jake brake as an advantage, probably more than the ability to get up the hill faster. I know that neither will compete with the red motor in this category, but I'm willing to give up something here for better fuel economy.
Electric Chicken
Well-Known Member
Paper loads are easily controlled downhill with my truck. Barely need the brakes going across 64 in Virginia.
ironpony
Professional Pot-Stirrer
The DD15 Jake does very well at 1500 rpm and up. a little weak below that. On a steeper grade that I'm not too worried about speed , I'll just keep it in 10th. If speed at the bottom is a concern, I'll drop to 9th and keep it below 1700 rpm. 6% grades near GCVW, drop to 7th or 8th depending on truck speed limit, engage the Jake, kick back and enjoy the scenery; might need to snub the speed occasionally with a tap of the brake.
Driven conservatively, the Prime guys turn up 9 and 10 mpg with the DD15/DT12 drive train.
Driven conservatively, the Prime guys turn up 9 and 10 mpg with the DD15/DT12 drive train.
Last edited:
Are you running a DD13 now?
Yeah, reviving this thread once again because I am flying through this new truck decision at the speed of a sloth, LOL.
Numbers for the 2020 model year. Going with the DD13 knocks off 400 pounds. Also knocks $1800 off the price of the truck.
Yes, sir!
Are you running more of a local run, regional run, or OTR? What kind of MPG's are you looking at?
More regional, in and out of Fargo for the last six weeks.
. You can't use my mpg as any kind of guide with our duty cycle. I'm thrilled to get above 5 mpg loaded, this time of year. You have to remember I'm normally running >70% engine load. I did run with one of the trucks with a 450 ISX, and got a tenth better over 300 miles even though I was 6k heavier and far dirtier aerodynamically. This is 505 hp, I believe.
Power seem to be good on the hills?
Does fine in the mountains. Power peak is 1625, so it's easy to keep it pulling hard without having to get revs up. Does need the revs for the Jake to come alive though.
mndriver
curmudgeon extraordinare
when I looked at the Cascadia evo last summer, if I were to go that route, I was getting the DD13 with a DT12 and having it set for the power torque. I forget exactly how it was coming together, but it would have been the 1850 torque. The DD15 doesn't have that option.
Now, my hard decision is fenwick or 13 Fishing.
Now, my hard decision is fenwick or 13 Fishing.
Finding fuel economy info on the DD13 is proving to be very difficult.
I feel like with the move toward downsped engines and higher gear ratios, along with improvements to the emissions, the DD13 might be the way to go.
Hard decision though, because once it's made, I am stuck with it.....
I feel like with the move toward downsped engines and higher gear ratios, along with improvements to the emissions, the DD13 might be the way to go.
Hard decision though, because once it's made, I am stuck with it.....
mndriver
curmudgeon extraordinare
every dealer I have spoken with regarding the fuel mileage issue won't touch the conversation. Too many variables and they know it.
The best I can get out of them is admitting that for a truck OTR on the road to expect to get 9mpg+ is unreasonable and the guys who are doing it are in special programs to include light loads etc to go with it.
So it's "rigged".
past that, they won't discuss it.
The best I can get out of them is admitting that for a truck OTR on the road to expect to get 9mpg+ is unreasonable and the guys who are doing it are in special programs to include light loads etc to go with it.
So it's "rigged".
past that, they won't discuss it.
Yeah, not expecting it from them. There is just little documentation anywhere specific to this engine. Where I keep my stats, it is only broken down by engine manufacturers, not the specific engine.
mndriver
curmudgeon extraordinare
Difference I see between a dd13 vs a dd15...
Kind of like a 12.7 vs a 14L series 60.
The dd13 though comes in a torque setting I'd want. The dd15 doesn't. End of comparison.
With the attitude of the gubbermint towards tuning engines nowadays, everything is staying stock
Kind of like a 12.7 vs a 14L series 60.
The dd13 though comes in a torque setting I'd want. The dd15 doesn't. End of comparison.
With the attitude of the gubbermint towards tuning engines nowadays, everything is staying stock
Similar threads
