Rear end gearing and upgrade...

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FullForceRam

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Hey guys,
I have a 2WD 14' Ram with 5.7 gas automatic on 3.55 stock gear ratio. I tow about 3-5 times a month (7x14 enclosed tandem axle trailer) On average I'm towing 3-5 times a month for events/shows and I've got about 4500-5K in tow on a plethora of different roads and hills throughout California.

I'm seriously considering upgrading to a 3.90 gear ratio

I know some of the pros and cons of changing gears, but aside from a little bit less MPG is there anything out of the oridinary on performing this myself that I should be aware of when I crack open and separate those axles?

Thanks.
 

co-pilot

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I didn't know they put 3.55's
Behind the 5.7?....hmmm

Anyway...are you running stock tire size?
 

Octane

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My '13 has the 5.7 with a 3.55.I have the 6spd tho.
 

RLJ10X

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I had 3.55s. 545RFE. They stunk. Out loud. I can't imagine suffering thru 3.21s.

The only downside is the initial cost. Other than that, there are only upsides.

Collectively, this forum cannot agree if there is an mpg detriment or not. The fluctuation in gas prices are probably going to be more impactful than lower gears.

I pull my 6500 pound trailer at least a dozen times a year. I did 4.10s. My truck does a damn good job here in the hills of southern Indiana.

You'll like lower gears. Splurge for some sort of posi-Trac while you're at it.
 

Daw14

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I put 456s in my 2014 and it is a different truck, I would not waste money just to go up to 392 . You will not regret going with 456. Do some more research on tow forums ,for more real world experiences.
 

62Blazer

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There is not much difference between 3.55 and 3.90. From my personal experience in several vehicles it would be very difficult to feel any difference in that amount of gearing change. Though at least it is only 2wd and you can do the work yourself the cost is minimal compared to a 4wd truck and paying a shop.
For gas mileage, again I doubt you would see anything significant with that amount of gearing change and it could possibly get better when towing. A big thing to remember is if you don't reprogram for the gears (or if changing tire size) the speedometer and odometer will be off and not give you accurate fuel economy results.
 

Daw14

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No reprogramming on my 2014 RCSB hemi for gear changes , tires I believe need an adjustment. But my speedometer is correct since switching from 355s. On 2500 s and bigger they need changes. I would bet good money your mileage gets better also. Go with 456 and smile every time you drive it.
 

Octane

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Difference in fuel economy would be negligible.At highway speeds especially, carrying a load with a lower gear ratio can actually improve fuel economy.
 
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FullForceRam

FullForceRam

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I have 22" tires. It pulls the trailer just fine but I know it could be better.
I'm not too concerned about MPG. Ive been doing some research and I too feel that 4.10 might be the ticket for my truck and applications. I'm pretty confident in my skills to have this done in my garage, the only item I need to look at is the backlash adjustments and any specific tool(s) needed for it.

I spoke to a local rear end shop in Livermore, CA and he was extremely knowledgeable. He said that they have placed 4.56 on Ram's, Toyotas, Jeep, but they have run into some issues with them. He stated that if I wanted to go with the 4.56 he recommends doing a micro polish on the gears so that they aren't as noisy and last longer. 4.10 he could use factory OEM parts and wouldn't need to do that and backs it up with a 3yr/50K warranty on parts and labor. All for $1400.00 which it didn't seem that bad for what I'm getting with peace of mind with a warranty.


running_board_3.jpg
 
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crackerjack1957

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I have 22" tires. It pulls the trailer just fine but I know it could be better.
I'm not too concerned about MPG. Ive been doing some research and I too feel that 4.10 might be the ticket for my truck and applications. I'm pretty confident in my skills to have this done in my garage, the only item I need to look at is the backlash adjustments and any specific tool(s) needed for it.

I spoke to a local rear end shop in Livermore, CA and he was extremely knowledgeable. He said that they have placed 4.56 on Ram's, Toyotas, Jeep, but they have run into some issues with them. He stated that if I wanted to go with the 4.56 he recommends doing a micro polish on the gears so that they aren't as noisy and last longer. 4.10 he could use factory OEM parts and wouldn't need to do that and backs it up with a 3yr/50K warranty on parts and labor. All for $1400.00 which it didn't seem that bad for what I'm getting with peace of mind with a warranty.


View attachment 468296
Gear ratio is determined by the tire size not the wheel/rim.
Yeah let those guys do it if you have never setup gears.
 
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FullForceRam

FullForceRam

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Gear ratio is determined by the tire size not the wheel/rim.
Yeah let those guys do it if you have never setup gears.
This will be the most likely scenario in having the shop do the work. To me, it's worth it especially with the warranty.
-SC
 

caulk04

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I was afraid I'd hate 3.21s in my truck but they're fine. Remember that your 1st gear is 3:1 where mine is 4.7:1. Even with your 4.10, my first gear is lower. Anyway, not trying to make this a contest.

Many moons ago I had a dakota with the RFE and swapped it from 3.55 to 4.56 and loved it. No way I'd go through the expense and not do 4.56 in a 4x4 Ram.
 
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