2016 Ram 2500 4x4 regear

[American Adventurist]

I'm about to regear. 2016 Ram 2500 4x4 CTD with OEM 3.42's and the 68RFE. Tires are 37 inch. With the armor and camper on as shown curb weight is about 10.5K. Right now, fuel efficiency sucks (12 mpg if I can baby it). Running a few lbs of boost most of the time is not helping. I have an Edge programmer (Juice with Attitude CTS2) sitting here in the box and while an economy tune "may" help, in the end it's about gearing.

So the question for you all here is, with 37's and a goal of increasing fuel efficiency, what is the "best" gear set? 4.11, 4.30 and 4.56 are all options. Thoughts?

 

[American Adventurist]

Also, LOVE the exhaust brake but am wondering what the consensus is on when to use/not use the tow/haul mode? Assuming that it effects programming and provides performance at the expense of efficiency just not quite sure "how" or "what" it effects/changes..

I'm new to the CTD world obviously but not completely inept so please excuse my noobish questions here.

 

[TWood]

A 4.10 gear swap would get you an effective gear ratio of about 3.83. A 3.73 gear swap would get you an effective gear ratio of about 3.34. If you ever wanted to go to a 35 inch tire you may not want anything larger than the 4.10 ratio. Your question about fuel economy is a tough one. Big trucks with big tires work really hard against good fuel economy. I'm not so sure that a gear swap is going to do a whole lot for your fuel mileage. Using a lower transmission gear for a while will probably give you an idea of what the gear swap may do for your economy. As far as the tow haul goes, I do not know everything it does but I believe it changes the shift points and will downshift automatically when you leave your foot off the go pedal. It seems to think that if you are in tow haul and you don't have your foot on the accelerator you must want the truck to stop or at least slow down dramatically. This is how it seems to work in my 2010 3500.

 

[Jim W]

I may be totally wet and incorrect on this, but if you re-gear to a higher numerical gear ratio such as 4:10's you not see an improvement in fuel mileage. Instead you will see a decrees in fuel mileage especially with 37" tires. In fact the best fuel mileage usually occurs with a differential gearing around 3:42 in the Ram trucks. That's why this is standard on the SRW trucks to improve the corporate fuel mileage numbers for HD trucks.

If you have weighed your truck and it is around 10.5K, that is pretty good fuel mileage for your truck. Case in point when I tow with my truck on pavement with my trailer, my trucks fuel mileage is between 10 and 11.5 MPG. I have seen it as low as 8 MPG when towing into a head wind. So 12 MPG is really great with your configuration.

My trucks configuration has the 6.7L Cummins, 68RFE, 4X4, 3:73 gears and LT285/70R17 126R Nitto Dural Grappler tires when towing.

 

[Cummins12V98]

Have you calculated different tire size when figuring mileage?

Personally I would leave the 3.42's. If I did change it would be to 4.10's.

 

[SnoKing]

Drive an extended fuel test in 5th gear. That will be close to what 4.10's will be like in 6th. Test will give you a good idea as to what the gear change will do for you. SNOKING

 

[American Adventurist]

Have you calculated different tire size when figuring mileage?

Personally I would leave the 3.42's. If I did change it would be to 4.10's.

Thanks for the inputs so far guys. I've been doing some research on my own and have a few thoughts.

From the factory, this truck came with 3.42 gears. Some of these trucks came factory with a 3.73 ratio, designed to have a proper run out with a stock size tire (roughly 31").

With my 37" tire and using cross multiplication, we can determine that in order to have the same RPM vs. speed as with the factory tire size, I would want to install a 4.45 gear ratio (3.73/31*37). Unfortunately, in this scenario there is no such thing as a 4.45 ratio, the closest readily available gear set is 4.30 or 4.56. Or, you can also opt to go with a slightly higher ratio of 4.11 that would give a slightly lower RPM vs. speed compared to stock. IMO that might be the best compromise for power band and fuel economy when cruising the interstate.

 

[AEdelheit]

We installed OEM 4.10 gears in our 2014 shop truck with 38" tires, it made the perform much better in all scenarios and the exhaust brake is noticeable more effective too.

 

[Deleted member 995608]

I vote 4:10's if you don't switch to a taller tire in the future.

 

[American Adventurist]

We installed OEM 4.10 gears in our 2014 shop truck with 38" tires, it made the perform much better in all scenarios and the exhaust brake is noticeable more effective too.

That's good to know, thank you for sharing that info.

 

[Regcabguy]

I've got the equivalent of 4.10's with my early G-56. I also haul around an 1800# popup. I wouldn't want any higher gears than I've got.
4.10's would be a good compromise.
EFI Live would be a safer tune for you using the Edge monitor to keep an eye on things.
Very nice setup.

 

[Bob4x4]

I've got the equivalent of 4.10's with my early G-56. I also haul around an 1800# popup. I wouldn't want any higher gears than I've got.
4.10's would be a good compromise.
EFI Live would be a safer tune for you using the Edge monitor to keep an eye on things.
Very nice setup.

But not 37's correct?
I am happy with my 41;0-37 combination unless towing at Cali speed limit

 

[Devilman]

I have 4.56 gears in my 15 with 37" toyos and it's perfect to me. I hated the stock 3.42 gears with the stock tires so I did the gear change when I did the suspension and 37s. Feels like the truck should've come stock with these gears.

 

[American Adventurist]

I have 4.56 gears in my 15 with 37" toyos and it's perfect to me. I hated the stock 3.42 gears with the stock tires so I did the gear change when I did the suspension and 37s. Feels like the truck should've come stock with these gears.

That's good to hear. Thing is, the Cummins makes enough power to turn the 37's just fine with 3.42 but it doesn't "feel" like it did on OEM 31's. Looking forward to be able to drive it without being a few lbs into the boost all the time...

 

[Devilman]

That's good to hear. Thing is, the Cummins makes enough power to turn the 37's just fine with 3.42 but it doesn't "feel" like it did on OEM 31's. Looking forward to be able to drive it without being a few lbs into the boost all the time...

Not to mention your trans will like you a lot more and last longer not having to lug so much. I went with AAM gears F & R but I don't think you can get the rear 4.56 gears from AAM anymore, seems they only made a short run of them and they don't show to be available anymore. I've got several buddies running Nitro Gear's re-gear package and I can't tell a difference between there's an mine, no gear whine or anything. They're just as good as AAM gears IMHO. Nitro also has a 4.30 gear set for the 13+ radius arm trucks and one of my buddies is running them in his 2016 2500 with the same Carli pintop kit as me and 37s and his has the same take off power as mine but he's about 150-200 rpm lower at 80 mph than me. I don't do a lot of highway driving so I went with 4.56s and my previous 06 I had 38s and 4.56s and loved it so I went with them again on my new truck and the 68rfe 6 spd trans makes it absolutely perfect to me.

 

[Regcabguy]

But not 37's correct?
I am happy with my 41;0-37 combination unless towing at Cali speed limit

No,37's would definitely require a DD. I'm still trying to wear out my 285's. 35's will be next. I could use some rpm relief but won't expect a fuel economy increase due to the increased weight and rolling resistance.

 

[American Adventurist]

Not to mention your trans will like you a lot more and last longer not having to lug so much. I went with AAM gears F & R but I don't think you can get the rear 4.56 gears from AAM anymore, seems they only made a short run of them and they don't show to be available anymore. I've got several buddies running Nitro Gear's re-gear package and I can't tell a difference between there's an mine, no gear whine or anything. They're just as good as AAM gears IMHO. Nitro also has a 4.30 gear set for the 13+ radius arm trucks and one of my buddies is running them in his 2016 2500 with the same Carli pintop kit as me and 37s and his has the same take off power as mine but he's about 150-200 rpm lower at 80 mph than me. I don't do a lot of highway driving so I went with 4.56s and my previous 06 I had 38s and 4.56s and loved it so I went with them again on my new truck and the 68rfe 6 spd trans makes it absolutely perfect to me.

Good to hear. I'm talking to Nitro now about their 4.30 gear set - it's a new design they say is stronger and quieter with an increase in ring diameter to 11.8"