I am looking to purchase a new 2500 cummins. I am looking at a 4wd crew short bed standard trans. My only hold up is what axle ratio should I get for the best tow mileage. I tow a 32 ft bumper pull toy hauler loaded weight 12000 lbs. It is as tall as most fifth wheels so it has a lot of wind drag. I tow about 15 to 20 weekends a year plus haul a ton of product to a customer about 12 times a year. The rest of my mileage is short trips to and from town. Anyway i currently drive a 06 Duramax with an Allison trans but really hate my 6 to 8 mpg tow mileage. I have had a 94 98 and 02 Dodge diesels all standard trans with 3:42 rear axle ratios but I didn't own the toy hauler at that time. I'm not big on the auto trans but I don't know how good the reliability is with the standard trans and newer motors. I used to be the guy to ask cause I studied every detail and got a lot of real world input. I no longer get all the input I used to so your input will be greatly appreciated.
Thanks in advance.

 

I averaged 12.9 towing to Co last year with my 4.10 and 18.3-19.8 empty - the 19.8 is winter, no AC. I have asked several times on this forum if 6th in the double OD autos can be used for heavy towing and nobody will answer me. That would be the deciding factor for me as to which ratio. My nv5600 is a towing beast and that's the very reason I held out til I found a 4.10. The 4.10 might not be so good with the 6sp auto if you can't tow in 6th. If 6th can't be used for towing, I'd rather have the 3.73. Craig

 

Thanks for the input. I drove a auto with 3:72 a couple says ago. The highway mileage seams decent but the acceleration mileage sucked. I know the torque converters lock up but that's once it has reached highway speed. I felt a lot of slip going on and I just feel the locked up standard trans would give better mileage when towing or when accelerating from a stop. A lot of my towing is small town to small town so there is a lot of stops and starts in a 300 mile trip.

 

The new engine don't get fuel mileage like they used to. I tow a 32 ft 5th wheel. Wish I had 4.10. emplty fuel mileage isn't that different and My friends with 4.10 get the same mileage as me, with similar mods, pulling 33 fter. We both get a consistant 12. I shift more.

 

I pull a 34' fifthwheel camper weighing in around 10,500# with my rig. I have the 3:73 gear and it does very well. I have the bully dog and keep it set on econ/tow setting. I typically get 20 - 21.5 mpg combined driving commuting to work and 12 - 17 mpg while pulling depending upon the hills; west TN (17), east TN (12). I've heard that the newer models don't do as well on mileage. Good luck and post your decision and results as you get some.

 

I drove a 2010 6 speed today. 2wd 3:42 axle. I was really disappointed the beat the average showed was 14.5 got 17 going down a low grade. The auto showed to do better but that's the computer on the truck. Just about decided to look for a used truck. Don't understand how the 2wd 6 speed could get worse mileage than the 4wd auto??

 

that 2010 a new truck?

 

Yes it was.

 

New trucks get lousy mieage. As soon as you pick 'em up from the dealer get the biggest load possible and haul it hard - preferably up a steep long hill - and 'burn' that sucker in. My 2007 5.9 6 spd did about 19mpg us until I did this now she quite often sees 23-24MPG empty and more power.

 

I never saw the asking about towing heavy in 6th on the auto but I have done it for 140,000 miles. Just over 100,000 of that is with the deletes and a smarty on level 3.
I was always a manual trans owner from 1990 til 2007. I bought a 5.9 auto and miled it out and not one problem. I then bought a Mega cab dually 4x4 6.7, stretched it and ran it til now...still going strong.

The manual trans in the newer trucks is geared a bit different then my 04 was...maybe someone can comment on it but I think the final gear is still a bit high compared to what the auto offers.

I have had zero issues with this truck since I got rid of the emissions stuff.

A friend of mine took delivery of a factory order 2010 and is going the way of the deletes before winter.

For me warranty is not the way I want to go if it means the truck is in the shop for 99% emissions related issues if I can resolve that myself by deleting.
My truck was used for work for 120,000 miles and it needed to be on the road. I also did not want to miss a wknd get away because of the truck in the shop. I save a lot of money on fuel now too.

With regards to your trailer and its height. The only thing I can suggest is a raised bed cap with an adjustable wind deflector towards the back of it to assist with sending the wind over the roof of the trailer. A friend of mine has a massive bumper pull toy hauler and once he did this, he had better mpg and easier times in the wind on the freeway.

Scotty

 

I just bought a 07 with the 6.7, auto and 3.73s, so far I am bone stock and pulling my TT which is a 26' bumper pull that weighs in around 7000 loaded I am getting around 12 to 13 going through the mountains of southern New Mexico. I just put the tranny in tow-haul mode and let the computer do the rest.

 

Im new to diesels. What do you mean when you are speaking of "deletes"?

 

Here is a link to the process:

https://www.dieseltruckresource.com/...t-t273345.html

 

My 06 is 6 speed G56 manual with 3.73's and it tows my 40' fifth wheel pretty well. The G has quite a bit shorter 6th gear than the NV5600 it replaced, but they revised the top gear ratio on the new trucks with the manual.

As far as reliability, the G56 shifts really well and seems to be a good strong transmission. The dual mass flywheel/clutch, though, gets mixed reviews. You hear about people having problems from time to time, but you also hear of people running stock power getting lots of miles out of them.

The auto choice in the new trucks is the double overdrive 6 speed 68RE. It seems to be pretty stout and I like the way it shifts better than the allison trucks I've gotten to drive recently. The top gear is really tall, and with 4.10's it turns lower RPM at highway speed than my truck does with 3.73's. The auto with 4.10's is also rated for quite a bit higher combined weight than you can get with the stick, so they must be pretty comfortable with its strength.

Anyway, for what you were doing, if it were me I'd probably go 3.73 if I chose the stick, and 4.10 if you get the auto.

With the last two dodges I've owned, MPG towing seems to vary hugely with speed, and not so much with RPM.


Welcome to the forum, and let us know what you decide.

 

I'd get 3.73 gears if you don't plan on bigger tires and I'd get 4.10s if you may possibly get bigger tires.


And I'd think 4.10s would help if you tow a lot....