Forum Discussion
60 Replies
- So I guess by locking out 6th and running 1800 rpm you gain a little responsiveness and have less gear hunting but it's going to cost something on fuel.
4x4ord wrote:
ShinerBock wrote:
Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."
But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???
This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.
When do you manually shift a transmission with stock tuning? What are you trying to accomplish by manually shifting?
I should have reworded that bnecause you can't actually shift manually in a Ram like you can in a Ford which is one thing I missed when I went from my F150 to my 2500 because there certain situations where it was helpful like starting the truck in second gear in slippery conditions. You only have the ability to lock out gears in the Ram and in this case I would lock out 6th to keep the truck from going into second over drive.
Both 5th and 6th are overdrive gears on the 68RFE as it is with most 6 speed transmissions. With a 3.42 rear end and 34 inch tires, 6th gear puts me in a great rpm unloaded(1,500 @ 75 mph) and 5th puts me in in the prefect rpm loaded(1,800 @ 65 mph).ShinerBock wrote:
Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."
But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???
This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.
When do you manually shift a transmission with stock tuning? What are you trying to accomplish by manually shifting?- The computer displayed mpg was almost exactly accurate on my 2011 Powerstroke. My 2016 lied and it was not always consistant in how much it lied by. Generally hand calculated proved to be about 8% better than the computer said. I used to check every tank but can't remember checking my 2017. I no longer fill with at a metered pump.
Cummins12V98 wrote:
Dead flat no wind conditions towing 29k combined thru Salem, Oregon on I-5 I would get the exact same mileage in 6th at 62mph as 5th. Once getting farther South around Eugene where the road started getting into the small hills It would pop in and out of 5th. I compared that mileage to locking 5th and 5th was a bit better. I finally just locked out 6th towing at 62 and would have my rpm's at around 1,750 and it performed flawlessly dropping gears as needed. With the 68 I could drop a gear once rpm's started dropping trying to hold my speed on a steep grade. Sometimes it worked and sometimes it made no difference.
With my 4.10's AISIN I tow in 6th same RPM as I did with the 68. I have tried dropping a gear once it starts loosing speed and it just stays where it needs to be and shifts as needed. It simply knows where to be.
They both worked great towing heavy but the 3.42's needed the lower starting gears on a grade the AISIN gives.
ONLY change to the AISIN I would like to see is the ability to lock out first and start in second while unloaded.
This has more to do with your 4.10 gears than it does having an Aisin. I would wager that a 4.10 68RFE would be the same since they both have the same 6th gear ratio although the 68RFE has a better 5th gear than the Aisin. Also, since the 68RFE has a 3.23 first gear instead of the 3.75 on the Aisin, I would bet that you would not want to start off in second gear.- Dead flat no wind conditions towing 29k combined thru Salem, Oregon on I-5 I would get the exact same mileage in 6th at 62mph as 5th. Once getting farther South around Eugene where the road started getting into the small hills It would pop in and out of 5th. I compared that mileage to locking 5th and 5th was a bit better. I finally just locked out 6th towing at 62 and would have my rpm's at around 1,750 and it performed flawlessly dropping gears as needed. With the 68 I could drop a gear once rpm's started dropping trying to hold my speed on a steep grade. Sometimes it worked and sometimes it made no difference.
With my 4.10's AISIN I tow in 6th same RPM as I did with the 68. I have tried dropping a gear once it starts loosing speed and it just stays where it needs to be and shifts as needed. It simply knows where to be.
They both worked great towing heavy but the 3.42's needed the lower starting gears on a grade the AISIN gives.
ONLY change to the AISIN I would like to see is the ability to lock out first and start in second while unloaded. Cummins12V98 wrote:
ShinerBock wrote:
Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."
But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???
This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.
I guess my 3.42 68RFE and 4.10 AISIN are the exception as they both have shifted and held gears as they should from solo to hauling 29-25k combined. Maybe cuz I ran the hell out of each right out of the box and ALWAYS run TH.
It is not a factor of holding gears or capability. My 68RFE and the Aisin 3.42's can easily hold 6th and the computer will be happy to keep you there towing at 1,500 rpm. However, this may not put you at the best rpm for efficiency and you may be using more fuel and boost to compensate for the lack of gearing just like how you would have to put more force on a shorter lever than you would with a longer one.
Both my friends/family who have Aisins and my 68RFE get better fuel mileage locking out 6th to keep the truck within the 1,800-2,100 rpm that Cummins recommends for the most efficient towing with the 6.7L. If you have a 4.10 gear, then locking out 6th may not be needed to get the best efficiency towing most loads because it will put you in these rpm ranges without it.ShinerBock wrote:
Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."
But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???
This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.
I guess my 3.42 68RFE and 4.10 AISIN are the exception as they both have shifted and held gears as they should from solo to hauling 29-25k combined. Maybe cuz I ran the hell out of each right out of the box and ALWAYS run TH.ford truck guy wrote:
Cummins12V98 wrote:
"He ran just short of 60 miles (55 ) without towing and averaged 23.2 mpg."
I thought "incredible" driving my new 11 HO DRW for the first time with 13 miles looking at the instant and average mileage. Fact is I didn't see those numbers after a few hundred miles.
I do hope those numbers hold true but I doubt it.
I will be able to verify that shortly.... I am hoping for similar results but mine was ordered with 3.55 , the one reporting has the 3.31. Although I Can't see that huge of a difference
Can't wait to hear from someone I know is a straight shooter!Cummins12V98 wrote:
"I agree that the computer may be more accurate for short runs which this one was. If they had burned 20 gallons or more then I would be more inclined to believe the hand calculated number."
It's simply the stupid way they do the click wait click fill that can in no way be accurate. Maybe someone is filling on the pump next to it??? Then the pump pressure will be different.
Fill that sucker to the top each time! I do it every time, sure it takes a few more minutes but I know EXACTLY what amount of fuel I used.
That tiny DEF nozzle is very sensitive, no way that is accurate.
Yet some find it strange that other care about "exactly" what amount of fuel they use.
Is it like a kid waiting for Santa as Christmas to see if you are .1 mpg better or .2 mpg worse than the last tank?
Is it a cause for consternation if somehow mileage was worse or celebration if it was better?
