Towing w/2500 6.4L

[hoboplayer]

New guy here. Hoping to get some advice from those who know a whole lot more than I do concerning towing with a Ram. I have a nearly new 2018, 2500 Ram 6.4 L gasser 2wd. I'm using it to tow a 10,200# 5th wheel. I think I made a mistake and allowed my Dodge salesman talk me into a 3.73 rear end. When I towed the new 5th wheel home empty (8,600#) I felt like the truck was always straining and ran in 5th gear on flat surface with no wind. My milage was 8 mpg.

With my new 2500 I towed my trailer about 2000 miles in mostly 4th and 5th gear. The truck always seems to be under a strain. My milage ran 7-8 mpg.

Previously I had a 2015 Ram 5.7 L gasser, 2wd, 3.92 rear end towing a 7800# trailer and the truck always felt like it had lots of power to spare and my milage was 9-14 mpg..

My questions are, should I change to a 3.92 or 4.10 rear end and how would this impact my milage? It seems to me that reducing the strain may actually help. Does this change require reprograming?

Your advice will be appreciated..............Don

 

[tjfdesmo]

Welcome to my world. The trans gearing is from the Cummins trucks, and is not optimized for this engine. My truck has 4.10s, and it is not much better. Tow/Haul in the 66RFE locks out 6th gear, and it loves to hang in 4th for miles and miles. I tow at 65, generally, and the terrain has to be just right for it to grab 5th, but if I bump it up to 67 or 68 it is more likely to use 5th. Or, I take it out of T/H and it will pull 5th no problem. My mpg pulling my toyhauler is generally 7.5-8.5. Sometimes a hair more, sometimes less. Admittedly, I am pulling a toyhauler that has me grossing 23K lbs, but I also have a flatbed that I haul with and it's not noticeably better.

I will be going back to a Cummins.

On Edit: You will get more accustomed to how the engine and trans work. I just set the cruise, and let it sing. For a gas motor, I gotta say the 6.4 is a hoss. The trans definitely hampers it.

 

[WAKEMASTER]

I have a similar setup with a lot more weight. I have been impressed with the 6.4. You just need to remember it is a gas motor. Under no circumstance will you have similar power and feel to that of a diesel. Just put the cruise on and let it shift where it wants to. Mine shifts between 3 & 4 gear on the highway. It will go to 5th if I am going down hill or completely flat surface with no wind. It get about 5-6 mpg towing my load. I don't know if I just got use to the motor but it seemed to have much more power after 8,000 miles.

 

[NewBlackDak]

If you are changing gears, go to 4.56. 4.10s off the lot is a no-brainer, but not enough change from 3.73 for the money spent.


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[hoboplayer]

Not exactly what I was hoping to hear. But thanks for the info. If I do change to the 4.56 would I loose mpg? Is this a Ram dealer change or can any shop do it? Also would this require a program change that has to be done by the dealer?

 

[NewBlackDak]

Not exactly what I was hoping to hear. But thanks for the info. If I do change to the 4.56 would I loose mpg? Is this a Ram dealer change or can any shop do it? Also would this require a program change that has to be done by the dealer?

Depends on your driving habits. Seems like everyone gets improvements in town and towing. Highway seems to stay the same or decrease very slightly. If you spend lots of time on the open highway doing 80-85 it’s likely to decrease. If your local terrain is hilly it’ll likely increase.

I don’t think the dealers will do anything not offered stock, but any competent axle or 4x4 shop be able to handle it.

No reprogramming. The speed sensors are outside of the differential.

There is a long thread on here with lots of details.




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[NewBlackDak]

https://www.ramforum.com/threads/6-4-hemi-gear-swap.77499/


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[GsRAM]

Gears will be your biggest bang for the buck. If I ever change I'm going to the 4.44aam (oem) 4.56s with my stock tires.

3.73 to 4.10 as said not near enough difference to justify the cost which will likely be in the 3k range for both axles.

I've always thought once your north of 10k lbs your in Cummins territory. The 6.4 will do the work but as you noted it'll appear strained...but it's actually not. Let it rev and work. Be diligent with your maintenance and you won't hurt it. Even with my 6k tt in the mountains it works. But once up in the rpm band she pulls like a freight train. I love it!

 

[mohemipar]

If you want dealer to do the install and keep your full warranty you'd probably have to go with the 4.44s from the chassis cabs as mentioned above. But you'd have to shop around and try to find a dealer that won't screw you and knows what they are doing.

DON'T do anything less than those 4.44s or you'd be wasting your money big time.

 

[hoboplayer]

Great Forum. Thanks for the help. I would have never considered going beyond 4.10. Guess it's time to shop for a price. By the way, what is the meaning of "4.44aam (oem) 4.56s". Is this something I should specify?

 

[tjfdesmo]

Some of the C&Cs run bigger ring and pinions, and are Dana, not AAM, so not applicable.

 

[mohemipar]

Doh forgot the chassis cabs use Danas. You get the nice wide track axles in the class 4/5 Rams and Fords.

Great Forum. Thanks for the help. I would have never considered going beyond 4.10. Guess it's time to shop for a price. By the way, what is the meaning of "4.44aam (oem) 4.56s". Is this something I should specify?

AAM (American Axle) is just the manufacturer. But as said above Dana does the chassis cabs. So dunno about that fitment.

 

[Ratket]

As everyone has stated, anywhere from 4:56 to 5:30”s will do the job. When you are towing you prolly won’t tow over 75MPH, as of late more and more people are re gearing- most go 4:56 to 4:88- and not one person has said “ What have I done” - they all praise it.

 

[GsRAM]

Yep exactly! If I was towing close to 10k with my truck I'd cough up the coin for 4.56s no question. Towing my 6k tt the 73s are fine, so I haven't bothered. If both axles could be done for 1-1500 I'd have to seriously consider regardless. That 3k price tag hurts....lol when I don't really need the steeper gearing.

 

[East0352]

I've got the 3.73 gears 4x4 with the 6.4L as well. I just pulled my new(er) 2005 Teton Experience 5th wheel to Houston from Dallas. I didn't notice any strain at all. I mean, I knew the trailer was back there, but it weighs 13,000lbs and it is a big parachute. Once up to 60, the Ram pulled no problem. I averaged about 10 mpg. On a couple of uphill, I was getting 8.5 mpg. Now, my 5th wheel is rated for 20,000 GVW and I plan to get a 1 ton diesel before pulling it anywhere else, but I know that if I need to, my 2500 Hemi will do the job.

As far as swapping gears, I would do not worry about the MPG's. If you change your driving habits to make use of the MDS, you would probably gain a few MPG with the exception of interstate speeds, but then again, my MDS doesn't kick in above 60-65 mph and the lower gears would probably help make 70 work. The question you should ask is, "Does the $3000 price tag for gears make up for the cost and resale of a diesel engine?" Unfortunately for me, a one ton is the only option I have to legally tow my trailer since it has a 20K GVW. From what I have seen, they get the same MPG, and the SRW 3500 has the same towing capacity as the 2500. I'm not looking forward to buying 6 tires all the time.

 

[CMV157]

The new 2020 will come with an 8 speed. That would be an awesome upgrade but probably not enough to trade mine in. Maybe someday. I'll keep buying mega millions and powerball.

 

[nmhuntr]

I only tow a few times a year so gas mileage is not a big deal to me while hauling. My mpg with 3.73 is about the same of better running empty as it was with my 1/2 ton Tundra so I got a lot more truck for the money. I saved a lot by not getting a the cummins. If I was going to tow once a month I would have gotten the Cummins no doubt about it.


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[ggrimm01]

Research this forum. These is alot of great info on this topic. Well I will give you my 2 cents worth. I just bought 2018 Tradesman with the 6.4L with the 3.73 gears and a 12.5K lb towing and 6'4" Bed 4x4. I also own a 2011 3500 Laramie Longhorn DRW with the 68RFE and 3.73's. However is does good with this setup. It is bone stock and pulls a 17K lb horse trailer. Using the 6.4L I want to tow the 17K horse-trailers once in awhile and after doing the math I could go with 4.30's of the 4.56's. With my driving and stock tires I feel the 4.56's would just be to high of a gear. The techs at Just differentials and the research from this forum helped me decide this course of action. Granted going down a steep grade in a gasoline engine is my biggest concern. On the Cummins I have the exhaust brake with is a necessity in the mountains. Most of the driving on the 6.4L will be local driving or puling a camper in the 7K to 8K range.

https://www.justdifferentials.com/Dodge-Ram-Gear-Package-p/gpram2500-select.htm

 

[Rbertalotto]

I recently went from a 2006, 5.7 diesel to a 2018, 6.4 Hemi with 373 gears. Pulling 8k pounds with both.

No issues with gas motor once I got used to all the shifting. Diesel got 12mpg towing and gas gets 10....both at cruise control set at 63mph.

Big difference is buying fuel on a long trip. Currently I'm driving from Massachusetts to Phoenix but way of Atlanta. I'm buying gas for $1.88 gal to $1.95 a gallon. I'm seeing Diesel at $2.56 to $2.89.....big difference on s long trip. Almost $27.00 in my pocket Everytime I fill up.
Bought truck in July 2028 and have just over 20k miles on it. Love the truck so far.
Diesel was exactly $8,000 more for identical truck.

Did a whole review on this subject on my web site..... www.rvbprecision.com

 

[KarL45]

Changing the gearing is a about the only way to get the 6.4 to pull without running in the higher rpm range. And even then, as the speed and rpm in low gear equate to 1000 rpm = 10 mph, (at 30 mph running only 3000 rpm) being on a long and hard pull with 10 or over in weight, almost a 4WD situation to get the gearing. Not good. I did re gear to 4.56 and although a bit of cost as I went through my dealer, night and day difference in performance. As for mileage "without" the trailer, better in town, about the same on the HI way, (in CO and elevations of 6 to 10,000) Lets just say, well worth the cost and a much better driving vehicle performance wise. Not the continual up and down shifting and pulling, from around 5000 rpm up, went to around 3ooo and now being able to run in the 5th and even 6th gear ranges with ease. Fact, If I were to do it again and pulling heavy, over 10k, would consider the 4.88 gearing. That would be optimal I think. Ps. I pulled a 38' 5er toy hauler weighing in between 13 and 14K. Cheaper changing gearing than a new vehicle?