Using Tow/Haul with Larger Tires

[MartyZ]

My main reason for venturing down this issue is my truck struggles with gear hunting a lot.
(2014 2500 5.7l)

So I have been reading around the forum and doing some research into the best way to compensate for my 37" Tires.

The Truck in its current state:
The axles have not been re-geared. (3:73)
Tire size is off in system (Gives a slower speed on the dash than real time. MPG is off)
Basically Bone Stock with a lift and larger tires.

One of my options is Alpha OBD;
This will correct the tire size in the system (and allow me to use my new mirror lights, separate project)

What I'm unsure of is how effective Alpha OBD will be at correcting my gear hunting.

Another option is re-gearing my axles to 4:10 to get my power back to the road.
I was really leaning this way (and still am a bit) but the cost is way over my budget right now and I'm not sure I would be able to do it myself in a timely manner.
The other concern is that I heard re-gearing wont fix all issues and you may still gear hunt, have speedometer off, etc.

So in the mean time I stumbled over a few threads where people had mentioned using Tow / Haul all the time and said they saw no negative effects and actually saw their gas mileage go up in some cases and a lot of restored power to the road.
I hadn't really used it too much because I wasn't sure if this would cause adverse wear & tear to my drive train. (Larger tires)

I decided to see its effects for a few weeks using it all the time:
The first thing I noticed was the RPMs were slightly higher (Normal) and engine braking was much more noticeable. (Also normal)
But what shocked me was that it didn't eliminate O/D (at least what I could tell) and when I was cruising at 55 (50 on the dash) it was not gear hunting or feeling sluggish. The RPMs were even lower than without Tow/Haul, it was riding below 2000.
The truck seems more responsive and comfortable in its gears.

Current MPG before using Tow / Haul: 8.9 (again, not accurate due to tire size, but well use it for reference)

I'm curious if anyone else has done this or knows something I'm missing, In the mean time I'm going to continue using it and giving some updates on here.

PS: If I'm going to break my truck, please slap me, Its my daily and cant afford to wear **** out quicker than FCA designs it to.

 

[ram1500rsm]

What’s your current gear ratio?
You want to address the tire size in your calibration and I’ll start there if I was you. This should help some. To address your gear hunting in full you either need to regear or move your shift points via TCM tuning.

 

[MartyZ]

My Current Axle gearing is 3:73.
So it is possible to fix it with both re-gearing and re-coding?

 

[MADDOG]

I don't think you have to go to the expense of re-gearing the vehicle. You can manually shift your transmission or tun it in Tow Haul mode as you have been doing. It won't hurt the transmission.

I ran into the same problem while in full automatic mode, especially around town.

I didn't use Tow/Haul mode but since my last three Rams had a gear selector button on the transmission stalk I would just use that to keep it from going beyond the selected gear.

3rd gear was good for most of my around town driving up to about 35 MPH. 4th gear up to 50 worked well. I used 5th up to 55 - 60 and when traveling at freeway speeds I went to full auto.

 

[NH RAM]

If you're running 37x13.5 on a 5.7 I wouldn't stop at 4.10 gearing, it's not going to be enough, go maybe to 4.88's or 5.13. Search the forum for those that have done it; here's a quick one that came up:
https://www.ramforum.com/threads/37-mts-with-which-gear-4-88-or-5-13.126016/page-2
I'd correct the speedo and swap gears.

 

[ram1500rsm]

Heck yeah, don't fear the gear with the 6 speed trans . If i could change my gears as easy as you guys with the HD trucks i'll jump to min 4.88's with 37's. I ran 37x12.5.17 with my factory 3.92's and it wasn't enough. I modified some of my shift points as well to live with it and drove for 12k miles. Im back to 35's and will settle in this size forever. lol

 

[MartyZ]

Well that's much better than what I dug up. Haha Thank you!
I'll price out a set of 4.88s or 5.13s instead.
Any Brands I should avoid? I'm not trying to sell an organ for them. But I also don't want to install Chinese trash in my baby.

 

[RamminMopar]

5.13, that 66rfe has long gears

 

[kurek]

Before you go shopping for any new gears go ahead and correct your speedometer/powertrain for the tire size first.

You can do that in Alfa or Jscan.... sadly these have become like mac/PC, android/iphone, blue or red politics, oil brands, tire brands, etc where everyone has a favorite - I only bring this up because I think changing tire size is faster and more intuitive in Jscan.

To answer the question you asked about that - YES updating your truck's powertrain to know your actual road speed with the larger tires will change how it shifts and drives it's not just for the nice-to-have benefit of an accurate speedometer and odomter.

Later if you decide to get gears anyway you'll still need Alfa or Jscan so it's not money wasted.

 

[MartyZ]

Before you go shopping for any new gears go ahead and correct your speedometer/powertrain for the tire size first.

You can do that in Alfa or Jscan.... sadly these have become like mac/PC, android/iphone, blue or red politics, oil brands, tire brands, etc where everyone has a favorite - I only bring this up because I think changing tire size is faster and more intuitive in Jscan.

To answer the question you asked about that - YES updating your truck's powertrain to know your actual road speed with the larger tires will change how it shifts and drives it's not just for the nice-to-have benefit of an accurate speedometer and odomter.

Later if you decide to get gears anyway you'll still need Alfa or Jscan so it's not money wasted.

I've never heard of Jscan before. I'll have to look into that. Looks like a coder is first on the list!
I am curious though, is it just the 1500s that need the gears welded in?

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[chris1126]

Well that's much better than what I dug up. Haha Thank you!
I'll price out a set of 4.88s or 5.13s instead.
Any Brands I should avoid? I'm not trying to sell an organ for them. But I also don't want to install Chinese trash in my baby.

STAY AWAY FROM NITRO GEARS!! their customer service is horrible.

 

[MartyZ]

Thank you and noted, that was one of the search results that kept coming up. Anybody recommend a better brand?

 

[chris1126]

Thank you and noted, that was one of the search results that kept coming up. Anybody recommend a better brand?

i went w nitro. had to fabricate my gears as they wouldnt seat properly. they said it was a design error and get this....they had to wait on the new design from china. then i questioned that cause they state AMERICAN MADE and they denied ever saying that. cost me an extra $800 to make their error correct. having said that, i have 37s and went w 4.56 gears. seems to be ok fir me but i would have prob chosen a diff ratio if i could/desired to redo.

 

[MartyZ]

i went w nitro. had to fabricate my gears as they wouldnt seat properly. they said it was a design error and get this....they had to wait on the new design from china. then i questioned that cause they state AMERICAN MADE and they denied ever saying that. cost me an extra $800 to make their error correct. having said that, i have 37s and went w 4.56 gears. seems to be ok fir me but i would have prob chosen a diff ratio if i could/desired to redo.

Wow, what a load of ****. That's exactly what I want to avoid if possible. What would you go with now after learning all of this if / when you can?

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[chris1126]

Wow, what a load of ****. That's exactly what I want to avoid if possible. What would you go with now after learning all of this if / when you can?

Sent from my Pixel 4 using Tapatalk

i have heard good about yukon. if i was to redo again id give them a shot.

 

[62Blazer]

I would go ahead and invest in AlphaOBD, or whatever device you choose to go with, and correct the tire size in the ECM first. This should be done regardless of what other modifications you do in the future, and if you do change the gearing you can use it to correct for it also.

For gears I wouldn't waste my time or money going from 3.73 to 4.10. I've personally made that change on my old truck years ago before I knew better and was very disappointed as you couldn't really tell any difference. Keep in mind the 4.10's are a factory option on all the 2500 series trucks and the standard ratio for Power Wagons with only 33" tires. You would need to go to a 4.56 just to get you back closer to the stock RPM range, and would maybe even consider 4.88.

 

[chris1126]

I would go ahead and invest in AlphaOBD, or whatever device you choose to go with, and correct the tire size in the ECM first. This should be done regardless of what other modifications you do in the future, and if you do change the gearing you can use it to correct for it also.

For gears I wouldn't waste my time or money going from 3.73 to 4.10. I've personally made that change on my old truck years ago before I knew better and was very disappointed as you couldn't really tell any difference. Keep in mind the 4.10's are a factory option on all the 2500 series trucks and the standard ratio for Power Wagons with only 33" tires. You would need to go to a 4.56 just to get you back closer to the stock RPM range, and would maybe even consider 4.88.

i would have to agree. 373-410 isnt gonna be a tremndous difference. 456 put me close to where i was w 373s.

 

[MartyZ]

https://www.dieselpowerproducts.com/yukon-front-ring-pinion-03-18-ram-hd

I found these in a 4.56, Yukons so I assume they are good.

 

[RamminMopar]

With that much truck I would really look into 4.88 or 5.13

 

[Burla]

You rfe is begging for an upgrade, regardless if you regear you have to watch these vids. 3.73 is fair, at least you dont have 3.55's. You should really watch those video's and consider what the pro's say on it. Get a gasket at a minimum, a plate even better if you have the extra cash and ensure that valve body never leaks, and tune for pressure and tire size, good thing if you get a tuner instead of alfa you can change shift points and never hunt for a gear again. I am not sure if alfa can change shift points, my guess is no unless someone knows different. When you have a 1/2 hour watch those vids found by hemi395 very informative.