auto trans vs manual ?

nukegm · Jun 18, 2017

manual trans vs auto in cummins diesel

any thoughts? i have an old 2002 dodge diesel with a 6 speed manual. it rips.

my 6.4 gasser 2016 with the automatic - is driving me nuts with the constant upshift/downshift....lugging etc...

im considering going back to a diesel, due to fuel economy. i throw 80 bucks every 4 days at my 6.4 in fuel.....that cost, extended to a month , would make up the price difference between a gasser and a diesel.

any input is appreciated.

thanks comrades!

RainDesert · Jun 19, 2017

I'm weighing a similar situation lately, I find myself driving more than I used to for work, and the 6.2 is not optimal in the mpg department for that.
I have been asking the same question about auto/G56 cummins. It seems it is not like it used to be with diesels and mpg. The auto gets the same mpg as the G56. My research has left me with; drive the manual because you want to shift and take away and possible auto annoyances, and if I deleted the truck the G56 would be less likely to have an issue under warranty that could get denied.

SouthTexan · Jun 19, 2017

From what I remember of how my truck drove without it being tuned and deleted, the Cummins with the 68RFE held gears just fine for the most part. The only time it would shift more often(although not a much as a gasser) was when the DPF was close to full. I noticed that it would not be able to hold 6th going up some hills at 55 mph when it was close to a regen while it would easily do it otherwise. Although preloading the turbo with a slight press of the throttle right before the truck started up the hill eliminated this. If you were going at least 65 mph then this was not an issue since you were high enough in the rpms.

Tuned and deleted, the truck hardly shifts. My trans tuning makes the truck shift into 4th at 30 mph, 5th at a 45 mph, and 6th at 55 mph. It will easily hold the gears all the way down to 900 rpm with light load which meas it downshift from 6th to 5th at around 45 mph and from 5th to 4th around 35 mph. Basically, once you are in 6th, you will be in 6th at speeds above 45 mph with normal driving even up slight hills.

I will say that with just a trans tune, the truck shifts damn near perfect. Oh, and you don't need to be deleted to get a trans tune. Calibrated Power now sells emissions legal engine and trans tuning.

BossHogg · Jun 19, 2017

RainDesert said:
if I deleted the truck the G56 would be less likely to have an issue under warranty that could get denied.

I've read the clutch is the weak point in the driveline.

Jimmy07 · Jun 19, 2017

nukegm said:
im considering going back to a diesel, due to fuel economy. i throw 80 bucks every 4 days at my 6.4 in fuel.....that cost, extended to a month , would make up the price difference between a gasser and a diesel.

thanks comrades!

If fuel mileage is the sole reason to switch back to diesel, then it would take you almost 400,000 miles just to recoup the extra $9000 upgrade for the Cummins. That's assuming the Cummins gets a solid 3mpg more than the hemi, and the price of the two fuels are the same, which, by me diesel is usually a little more than gas

nukegm · Jun 19, 2017

thanks for the info comrades....i have read on this forum the cummins gets 20 plus. i have no idea if thats hot air or not....currently i get high 10s hand calcuated. along with the transmission never seemingly happy in almost any gear, is why im considering going back to the cummins....had i done my homework when i ordered the truck, i should have gotten the 4.10 diffs instead of the 3.73 currently.

additionally, turbos like elevation. i live at 9300 feet.

cheers!

TITAN-O8 · Jun 19, 2017

I just bought got my truck with the G56 and love it. Shifts smooth and drives nice. My dad has a 3500 with the 68rfe. We have cattle and when his truck is loaded I hate the way it shifts. I'm a truck driver so I prefer to decide when the transmission shifts. Even though you lose a little HP and torque I can replace alot of clutches for the cost of 1 automatic trans.

BossHogg · Jun 20, 2017

nukegm said:
i have read on this forum the cummins gets 20 plus. i have no idea if thats hot air or not....

The experts are the first to chime up that MPGs are more about driving style. With that said, my 2015 3500 Cummins with the 68RFE will average 22 to 24 MPGs depending on the mix of city and freeway travel. This seems to be inline with others but I've also read posts of 19 MPGs and less.

I'm old, not interested in jack-rabbit starts or constant throttling, that may be the difference.

SouthTexan · Jun 20, 2017

I didn't get any where near 20 mpg before deleting or even after for that matter. However, I have +1 inch aggressive Ridge Grappler tires, live in a state where most highways are 75 mph, and I am not light on the throttle. I have no doubts that if I still had stock tires, drove about 65-70 mph on the highways, and tried to get better fuel economy then I would. For now, I am happy with the 17.5 mpg (hand calculated) average that I normally get each tank.

theviking · Jun 20, 2017

Won't help with your fuel economy but the HF tune definitely helps with the trans tuning. Holds the gears longer and shift points are much more user friendly.

auto trans vs manual ?

nukegm

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RainDesert

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SouthTexan

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BossHogg

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Jimmy07

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nukegm

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TITAN-O8

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BossHogg

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SouthTexan

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theviking

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