Question for owners of late model Ram 2500 6.7 Cummins Diesel Owners

[SteveH]

I don't expect to get a lot of response from this question because it is rather specific, but can't think of another way to get the data.

If you are towing with the above specifically mentioned vehicle, say 2011 and newer, what gear ratio do you have in your truck, what are you towing, and what is your typical towing fuel mileage?

I am asking this question because I'm considering changing the gears in my truck from 3.42 to 3.73, because by the specs that I have found, I'm over the limit as currently loaded.

I've tried the Cummins forum, but the majority of those guys are young hot rodders, and don't really give a flip about towing or fuel mileage.

Thanks for any input you may have.

[Skater]

We have the stock gearset, tow a 30' Airstream, and we're seeing 13.6 mpg overall, mostly towing (usually on hills, too). Note it's a new truck - we only have 2,500 miles on it - so I wouldn't be surprised to see it increase as it breaks in.

The overall average is calculated using the sum of the trip odometer readings divided by the sum of the gallons put in, just in case you're using a different calculation.

[The Ice Man]

We have a 2012 2500HD, 6.7 Long Bed with a 3.73 rear end, 19000 miles on the dial. We tow a 27FB pretty fully loaded We finished a 3900 miles trip from Tucson through Utah, Idaho and Western and Central Montana (including the construction detour over Mt. Washburn in Yellowstone) in September. We crossed the Continental Divide 4 times. We averaged 13.36 miles per gallon, measured as above (total miles/total gals.).

We filled up a mile from the house on the way out and the same coming in for a landing. Fuel quantity measured by the station's automatic shut-off.

[slowmover]

With your level of engine power versus loaded combined weight I really don't see an advantage given the 68-series auto trans.

The only ones I've known to change the gear set was in oilfield hotshot, and then because the gross was exceeding 30,000-lbs.

The six speed autos really changed things. Your change is equivalent to running 4.11 gears in the old days. Gives the TV more punch but highway rpms hurt FE.

FWIW, I am still considering changing from 3.73 to 3.42 on my 305/555 2004 to have the long-distance cruise rpm as well as city rpm in the fuel economy sweet spot. Mine has not the power rating of yours but with the six speed manual I have a good deal of control over operational rpm.

That said, I am still weighing it against higher altitude losses. I don't much care about ascent speeds. But there will be a trade off some where I may not like.

Put your question up on TDR after a search. That crowd is more likely to give you a fair appraisal. I'll guess that none of them will find your GCWR of any concern.

I'd be more inclined to delete the truck as your question is about available engine power. As I believe even mine is overpowered for the task (18k likely max) I also see higher gearing as an option as above.

[SteveH]

The reason I am concerned is because I am over the gross rating, and had one instance last year where I had to stop on about a 7% uphill grade for construction at about 10,500 feet, and for a while didn't think the rig would get going again.

When it did finally untrack, the front of the truck was bouncing like a 18 wheeler that popped the clutch at a red light. That's got to put some stress on things like drive shafts.

[slowmover]

That, sir, is the dilemma to pose to the wise heads on TDR.

OTOH, it is part of using the truck like truck. Remember that the hotshot crowd is doing that weekly. Trucks last about 300k with one or more clutch or trans rebuild.

As you are retired and the truck something of a dedicated TV, then gears, delete and trans components are worth looking at.

But as the 2014+ trucks are a real jump forward -- and you are not overjoyed by yours -- it may be worth looking at the changes and better configurations possible.

[J. Morgan]

I think maybe you are over thinking things.

If the truck pulls well it should be cool.

That engine should have more than enough torque to deal with your Airstream no matter the ratio.

Plus,,, lower gearing may well render your first gear essentially worthless.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[tjdonahoe]

4 door short box with 6.7 . 3.73 ratio ,6 speed auto my actual average on a 4000 mile trip is 12.. No matter if we go to calif, or to Maine...You got to remember the 5 the gear is over drive..it runs at 64 ish at 1500 rpm about like my big truck..2007..

[tjdonahoe]

I just found the dodge guide 2014 model...6.7 6 speed manual transmission, 3,42 gears, GCWR is.....24000 lbs 1000 less than 25000 lbs for the auto.17000 lbs max loaded trailer weight, so how are you over loaded, unless you have a very large dog....

[SteveH]

Originally Posted by tjdonahoe

I just found the dodge guide 2014 model...6.7 6 speed manual transmission, 3,42 gears, GCWR is.....24000 lbs 1000 less than 25000 lbs for the auto.17000 lbs max loaded trailer weight, so how are you over loaded, unless you have a very large dog....

Yes, I've seen those numbers and they are part of what confuse me. I do not have a 2014, but a 2012, and the numbers are here on this chart: http://www.google.com/url?sa=t&rct=j...82001339,d.aWw

Check for a Laramie Crew Cab Short Bed, 2500 4X4, auto trans, with the 6.7L engine, and you will see the max towing is 9550lbs, and GCWR is 17,000. My trailer GVW is 11,500, and my scaled combined weight is 18,100 lightly loaded.

So, my real question is, why is a 2014 rated to tow more than the 2012 with the same equipment?

[J. Morgan]

Tow ratings ain't all about equipment as much as they are about product liability and generating sales.

The market pushes these things around.

Could be that in 12 they wanted to sell more one ton trucks, and it could be that in 14 a competing brand rated their 3/4 tons higher so Dodge followed suit to maintain market share.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

[slowmover]

And it is the wheel/tire ratings that matter. The others are more in the way of suggestion.

[SteveH]

Originally Posted by J. Morgan

Tow ratings ain't all about equipment as much as they are about product liability and generating sales.

The market pushes these things around.

Could be that in 12 they wanted to sell more one ton trucks, and it could be that in 14 a competing brand rated their 3/4 tons higher so Dodge followed suit to maintain market share.


1/2 Ton 4WD Truck, 72 Sovereign Hensley Arrow

J., I am beginning to believe you are correct. I've not talked to Chrysler about this because normally you can't find anyone with any real knowledge, and whoever you find that will talk with you feeds you a line of sunshine just to get rid of you.

Think this might be another example for the need of standard SAE ratings.

Been towing like this for a year, probably 14,000 miles, and nothing has broken or fallen off (knock on wood, and watch for the bus load of orphans).

[slowmover]

SAE J2807 is also fraught with assumptions not always pertaining to what a vehicle can do.

[SteveH]

Originally Posted by slowmover

SAE J2807 is also fraught with assumptions not always pertaining to what a vehicle can do.

Yea, maybe so, but it would seem to me that any kind of standard is better than the manufacturers pulling numbers out of their orifice.

[rostam]

Originally Posted by slowmover

SAE J2807 is also fraught with assumptions not always pertaining to what a vehicle can do.

Before J2807 auto manufacturers could pull a number out of thin and and slap it on their vehicles. Now, they have to pass a set of well defined standardized tests. IMO, this seems like a big step in the right direction.

J2807 tests the following:

1) Cooling capability on a long highway upgrade modeled on the Davis Dam grade on Arizona SR 68;

2) Launch and acceleration performance on a level road and a 12 percent upgrade;

3) Combined handling performance – understeer and trailer sway;

4) Combined braking performance – stopping distance and parking brake-hold on grade; and

5) Structural performance for the vehicle and hitch or hitch receiver.

J2807 assumes the following:

a) For light-duty full-size pickups (GVWR < 8,500 lbs.), SAE J2807 assumes that the tow vehicle includes any options with higher than 33 percent penetration;

b) It assumes there is both a driver and passenger in the vehicle, each weighing 150 pounds;

c) It assumes that tow vehicles also include up to 70 pounds of aftermarket hitch equipment (where applicable); and

d) For conventional trailer towing, SAE J2807 assumes that 10 percent of the trailer weight is on the tongue.

The tests seems comprehensive to me. I'm sure it can be improved upon, and will be improved as time goes on -- I'd say the 150# driver and passenger is unrealistic.

Originally Posted by slowmover

And it is the wheel/tire ratings that matter. The others are more in the way of suggestion.

May I ask how you came up with this opinion? Almost, any user manual I've read clearly states the opposite -- they are not suggestions.

[tjdonahoe]

I will bet everything is fine, I sure wouldn't be afraid of it, and I darn sure wouldn't even think about changing the ratios, keep them, I would like to try a higher ratio,and run the engine slower..I know the new 3/4 t rams have coils on the rear??

[SteveH]

Originally Posted by tjdonahoe

I will bet everything is fine, I sure wouldn't be afraid of it, and I darn sure wouldn't even think about changing the ratios, keep them, I would like to try a higher ratio,and run the engine slower..I know the new 3/4 t rams have coils on the rear??

Yes, they are coil. Mine is leaf.

[slowmover]

Originally Posted by rostam

Before J2807 auto manufacturers could pull a number out of thin and and slap it on their vehicles. Now, they have to pass a set of well defined standardized tests. IMO, this seems like a big step in the right direction.

J2807 tests the following:

1) Cooling capability on a long highway upgrade modeled on the Davis Dam grade on Arizona SR 68;

2) Launch and acceleration performance on a level road and a 12 percent upgrade;

3) Combined handling performance – understeer and trailer sway;

4) Combined braking performance – stopping distance and parking brake-hold on grade; and

5) Structural performance for the vehicle and hitch or hitch receiver.

J2807 assumes the following:

a) For light-duty full-size pickups (GVWR < 8,500 lbs.), SAE J2807 assumes that the tow vehicle includes any options with higher than 33 percent penetration;

b) It assumes there is both a driver and passenger in the vehicle, each weighing 150 pounds;

c) It assumes that tow vehicles also include up to 70 pounds of aftermarket hitch equipment (where applicable); and

d) For conventional trailer towing, SAE J2807 assumes that 10 percent of the trailer weight is on the tongue.

The tests seems comprehensive to me. I'm sure it can be improved upon, and will be improved as time goes on -- I'd say the 150# driver and passenger is unrealistic.



May I ask how you came up with this opinion? Almost, any user manual I've read clearly states the opposite -- they are not suggestions.

Tires and wheels and axle ratings are the thing. It is the only legal requirement. For those who currently or have previously used these trucks to make a living. This is what DOT checks. What the scale house looks at.

[tjdonahoe]

Sounds like you want to upgrade to one of them BMW'S with all wheel drive and them 130 mile brakes!