Does my usage warrant diesel? Cummins 6.7 with AISIN...

[Danattherock]

First of all, having read many, many, old threads here. I want to say up front, the initial cost of the diesel, gas mileage, and ongoing cost of regular oil changes and maintenance are not considerations with my decision. My only concern is which motor will be most reliable in the years to come.

Wife and I have decided on Dodge 3500 Mega cab Laramie SRW 4x4. Hauling 27-28' Airstream (7-8k lbs) through Smoky Mountains of NC and Tenn a weekend or two each month and a big 2-3 week trip each summer out west is main towing usage.

My concern, my daily driving is just 5-7 miles (45-55 mph) into and from town, once weekly driving 30 miles away and back seeing family. And once a month 2.5 hours away to the coast to see family. Sometimes more highway driving, but this is the minimum average.

Then soon adding an Airstream, which we plan to do soon after buying TV. We will take at least one weekend trip a month to the Smoky Mountains of NC and Tenn which is 4-5 hours one way.

Is that enough to keep a diesel happy?

Read they need to be driven a lot to 'clean out'. Read various ramblings about 'Regen', throwing 'Error codes', and such, but not sure how much driving style plays into this. My concern is my driving style may better suit the gas 6.4 Hemi.

An additional variable, I'm very interested in the AISIN $2400 transmission upgrade, but it's only available in the Ram 3500 with Cummins 6.7 diesel. So if going with gas, I don't have this option available to me. Anyone familiar with AISIN? Would love to hear about it.

Our primary goal is to have a long trouble free engine life. Plan is to keep truck a long time. We don't buy new cars often. We take care of them and keep them around. My main question is for our intended usage, do you think the Cummins or Hemi 6.4 would be best?

Thanks for any insights you may share.


Dan
NC

[Danattherock]

That's great info. Thank you. Will check into that further.


Edit, just saw video. That's awesome.


Dan

[noteven]

Hi Danattherock:

I bought through the AirSafe website: AirSafe website

If you don't tow a bunch of different trailers like our truck does, I would suggest talking to them about sizing your hitch to your Airstream - main reason is the big trailer capacity units are heavy to lift 🙂 - I have a Class VI model and with a weight distribution coupler bolted to it I could use a skyhook to help pick it up...

When towing you adjust the air pressure per instructions so the dog bone connectors ride just slanted a bit. When the trailer goes to give the tow vehicle (and it's driveline and occupants) a shove (rv world calls it "chucking") the AirSafe compresses absorbing most of that energy.

We have on board air we can use for adjusting the hitch suspension air pressure but it would be just as easy to buy a decent quality hand tire pump for the tiny changes that are needed - due to load, outside temperature, and big changes in altitude. It is not fiddly - if you set it for the trailer once, and don't climb 6000ft in altitude or go from winter to summer in a day it doesn't need a lot of adjusting...

[Danattherock]

I have read of many similar opinions on the Airsafe hitch. Thanks man. We will look into that. Most our energy so far has been in picking out suitable sized Airstream and a good tow vehicle. We have lots to learn about the ever important connecting of the two.

What kind of place sells or installs Airsafe? Car dealer or RV dealer? Or other?


Dan

[noteven]

06Fargo wrote:
- side notes to the sand throwing contest so far - I read that the FLT guys contacted Chrysler about the 6.4's performance - apparently the engine is programmed to settle back into a climbing rpm to pull a long grade if the driver holds it in racer mode rather than truck driver mode - pedal to the rug - revving to the governor try an upshift - no can't pull that gear - downshift- rev to the governor and repeat... its not really designed as a hill racer it behaves more like a truck engine...

ib516 - thanks for digging up the correct information around what I was trying to say back on page 5 regarding how the 6.4 is programmed to work on long grades...

To the OP - we use an AirSafe suspension receiver hitch for towing light trailers with our 3500 so the ton truck doesn't beat on the trailer on rough roads, bridge decks, and RR tracks. It is a great piece of kit...you can see the trailer front working 3 to 4 inches of travel independent of the pickup.

[blofgren]

ib516 wrote:
If you haven't ever read it before, the tfl guys posted a follow up to the Ike gauntlet test of the 6.4 Hemi after hearing from Ram engineers.

We spoke with Ram and here's what they said about the slower Results of this Ike Gauntlet Run: "During the Silverado drive, you spoke negatively of the shift calibration. The tested Chevy was we assume hunting between 1st and 2nd, and ranged from 5300 rpm to around 2800 rpm, which you didn’t seem to like. The Chevy revved very high up the hill for extended periods of time, over 5000 rpm.

Ram Truck “invented” the first gear hold feature – and calibrated it – to avoid gear hunting and driving at excessively high rpm’s.
Ike is a variable grade and we worked hard to develop a calibration that appropriately manages torque on the run and other grades.

We don’t want the truck to rev high for extended periods of time and purposely hold 4,200 rpm.

Bottom line – our truck performed exactly as expected by delivering a more comfortable hauling experience, better vehicle longevity and improved fuel economy. Time to the top of the hill is only one small piece of the driving experience and our engineers take a number of variable into consideration. Ask yourself if just over one minute is worth other negative driver inputs."

I do remember reading that and believe there is something to it because that is exactly how that truck seemed to act in that test.

[ib516]

If you haven't ever read it before, the tfl guys posted a follow up to the Ike gauntlet test of the 6.4 Hemi after hearing from Ram engineers.

We spoke with Ram and here's what they said about the slower Results of this Ike Gauntlet Run: "During the Silverado drive, you spoke negatively of the shift calibration. The tested Chevy was we assume hunting between 1st and 2nd, and ranged from 5300 rpm to around 2800 rpm, which you didn’t seem to like. The Chevy revved very high up the hill for extended periods of time, over 5000 rpm.

Ram Truck “invented” the first gear hold feature – and calibrated it – to avoid gear hunting and driving at excessively high rpm’s.
Ike is a variable grade and we worked hard to develop a calibration that appropriately manages torque on the run and other grades.

We don’t want the truck to rev high for extended periods of time and purposely hold 4,200 rpm.

Bottom line – our truck performed exactly as expected by delivering a more comfortable hauling experience, better vehicle longevity and improved fuel economy. Time to the top of the hill is only one small piece of the driving experience and our engineers take a number of variable into consideration. Ask yourself if just over one minute is worth other negative driver inputs."

[ib516]

I have also been theorizing as to why they chose the "higher" 2nd gear ratio. My truck will do 70 mph in 2nd gear, even with the 4.10 axle. I wonder if they use that ratio to enable 2nd gear to be useful for highway passing or pulling grades with a load.

I know the tq converter doesn't lock in 1st gear so that (prevents excessive heat build up) might also be a reason they limit the rpm.

[ib516]

IdaD wrote:
It failed because because it didn't have enough power or torque to upshift because the ratios aren't well matched to the 6.4. I doubt it would be an issue with your trailer or most situations, but it does hamper the engine. There was a guy from Colorado on here a month or two ago who was ready to trade because he ran into similar issues as you saw on that YouTube video. I'm not sure what came of it but I'm sure you can search and find the thread. He got stuck going 30 mph or something on some grades. Again not likely something you'll run into very often. I think not having the exhaust brake maybe a bigger tradeoff. That thing rocks.

I disagree. I think (and Ram engineers say) it is programmed to act that way when in that situation. I don't think it's a lack of power, the thing has 410 hp!

I also wonder if that Ike test has anything to do with the 89 octane required in 2015 models? Admittedly pure speculation.

[IdaD]

I did test drive one, i have not towed with one. Tow/haul mode doesn't change the ratio spacing, which is the issue.

[Danattherock]

Again, what role would using tow/haul mode play in improving that condition? Seems taking control over gear selection and shift points would have to help. The folks I've heard from that own a Ram seem to be using the tow/haul mode almost exclusively when pulling a trailer or camper. Many also seem to favor a 4.10 rear diff.

And you can manually shift to another gear using tow/haul to slow your decent on the way down, working in similar capacity to a diesel brake. I've heard from many folks owning a 6.4 Hemi that this was a very effective technique and they only have to lightly and sporadically apply the brakes in many instances.

Have you actually driven one of these trucks with 6.4 Hemi and 66RFE or are you passing on stuff you've read? Not being sarcastic, just curious where the insights are coming from. Typed dialogue is difficult, I'm just curious what your experience is with this engine/transmission. Thanks.

Dan

[IdaD]

It failed because because it didn't have enough power or torque to upshift because the ratios aren't well matched to the 6.4. I doubt it would be an issue with your trailer or most situations, but it does hamper the engine. There was a guy from Colorado on here a month or two ago who was ready to trade because he ran into similar issues as you saw on that YouTube video. I'm not sure what came of it but I'm sure you can search and find the thread. He got stuck going 30 mph or something on some grades. Again not likely something you'll run into very often. I think not having the exhaust brake maybe a bigger tradeoff. That thing rocks.

[Danattherock]

Thanks for that IdaD.

Had read about 66, got my numbers crossed. Regarding the issues with this transmission that you refer to. Is this something that would be improved on by using the tow/haul mode and some common sense?

Seems choosing 2nd rather than listening to the truck struggle in another gear would be 'common sense'. I saw the miserable performance of the 6.4 Hemi in TFL truck Ike Gauntlet YouTube video.

What I failed to catch initially is that they just put it in drive and drove up one of the steepest highway grades in North America without ever using tow/haul mode or manually taking control over gear selection or shift points. It's like they were trying to make the truck fail.


Dan

[IdaD]

Danattherock wrote:
^^^^ that's good to hear man.


I also read lots of stuff about the 68RFE having issues. Hopefully just web ramblings and BS. But for folks like me not familiar with trucks, it was bad to hear. It led me towards wanting the AISIN, which requires Cummins diesel, and a 3500 one ton. Viscous cycle.

But I heard from lots of folks that loved the 68RFE and slowly my mind changed, or opened I should say. That led to me deciding on a Mega cab 2500 with Hemi, with 68RFE transmission, and 4.10 rear diff. Will be a special order 2016 Laramie Limited 4x4.

As for the above comment about flat lands in Canada, he tows a 12k lb 5er through the Canadian Rockies. I saw his YouTube 8 min video and that Hemi had that 12k lbs rolling quickly. There is no short supply of power in that 410 horse Hemi!!


Dan

The Hemi has the 66RFE, not the 68RFE that the Cummins gets. The ratios are problematic in certain mountain towing situations. Particularly at altitude.

[IdaD]

Cummins12V98 wrote:
" 68RFE doesn't really have a great reputation "

Where do you get this impression? The 68RFE is a great transmission with very few issues. 65K on mine towed a combined30K load at least 1/2 of those miles even had the wrong 3:42 gears never even a burp!

The 68 has a pretty good reputation and is reliable unless you tune. The 66 in the hemi has a good reputation with respect to reliability but the ratios arent well spaced for the gasser. I think they're the same as the 68 with CTD, but you're working with about half the torque.

[Danattherock]

^^^^ that's good to hear man.


I also read lots of stuff about the 68RFE having issues. Hopefully just web ramblings and BS. But for folks like me not familiar with trucks, it was bad to hear. It led me towards wanting the AISIN, which requires Cummins diesel, and a 3500 one ton. Viscous cycle.

But I heard from lots of folks that loved the 68RFE and slowly my mind changed, or opened I should say. That led to me deciding on a Mega cab 2500 with Hemi, with 68RFE transmission, and 4.10 rear diff. Will be a special order 2016 Laramie Limited 4x4 Mega Cab.

As for the above comment about flat lands in Canada, he tows a 12k lb 5er through the Canadian Rockies. I saw his YouTube 8 min video and that Hemi had that 12k lbs rolling quickly. There is no short supply of power in that 410 horse Hemi!!


Dan