Regretting ordering 3.92 on my 22 Ram Ecodiesel and almost debating paying to downgrade to 3.21

[dirish613]

Hi, I had ordered my RAM with 3.92 ratio as I only seemed to come across the good articles at that time in which I learned that it will have a higher resale value in the future, better for towing, etc. I did see some mention of a negligible difference in mpg but thought nothing of it as the sticker did not update on the MPG at all after I selected 3.92. I had even picked up the bigger diesel tank because I wanted to be able to go on long trips while dreaming about the 29mpg thats advertised lmao.

I live in California, almost everyone and their mother drives 80mph here on the highways and most drive even faster. I live in a fairly rural area, I have to drive on the highways a fair bit in order to get most things.
In my first few weeks of testing, here's what I've noticed for mpg
80mph = 2200 rpm and ~20mpg
75mph = Just over 2000 rpm and ~24mpg
70mph = I dont remember the exact rpm but its 27+mpg

I did reach out to the service department at my local dealer and was told $2,750 + labor in order to switch to a 3.21 (guy sent me a detailed parts list as for the breakdown) and I'm following up with them now to see how much labor that would be.

In terms of switching over
Pros:
For the most part I can drive as I normally do and not have to worry about being inefficient in terms of diesel
Would be saving time as well as I'd be driving at 80mph instead of 70/75

Cons:
The upfront cost of course
Potential resale value in the future may be impacted but I dont like switching cars very often
Towing impact, I dont tow much now but it was just futureproofing


You may be calling me crazy but this is bothering me so much, like how did I look into every little detail and end up making this big of a mistake. Also, I am under the assumption that going to 3.21 will give me lower RPM's at 80mph, please correct me if I'm wrong.

I can run my 6.7 Cummins at 95 MPH and only turn 1600-1700 RPM. Don’t believe anyone that tells you it’s about wind and drag. When fuel went through the roof I backed it down to 70MPH back and forth to work. I drive 40 miles round trip everyday on a highway and I am getting between 21 and 23 MPG keeping it there. I drove out to the coast last week on some older back roads and kept it at 55 MPH and got over 25 MPG. Gear ratio does matter! If you aren’t towing you don’t need the higher gear or you’re always over revving the motor.

 

[Rod H]

Hi, I had ordered my RAM with 3.92 ratio as I only seemed to come across the good articles at that time in which I learned that it will have a higher resale value in the future, better for towing, etc. I did see some mention of a negligible difference in mpg but thought nothing of it as the sticker did not update on the MPG at all after I selected 3.92. I had even picked up the bigger diesel tank because I wanted to be able to go on long trips while dreaming about the 29mpg thats advertised lmao.

I live in California, almost everyone and their mother drives 80mph here on the highways and most drive even faster. I live in a fairly rural area, I have to drive on the highways a fair bit in order to get most things.
In my first few weeks of testing, here's what I've noticed for mpg
80mph = 2200 rpm and ~20mpg
75mph = Just over 2000 rpm and ~24mpg
70mph = I dont remember the exact rpm but its 27+mpg

I did reach out to the service department at my local dealer and was told $2,750 + labor in order to switch to a 3.21 (guy sent me a detailed parts list as for the breakdown) and I'm following up with them now to see how much labor that would be.

In terms of switching over
Pros:
For the most part I can drive as I normally do and not have to worry about being inefficient in terms of diesel
Would be saving time as well as I'd be driving at 80mph instead of 70/75

Cons:
The upfront cost of course
Potential resale value in the future may be impacted but I dont like switching cars very often
Towing impact, I dont tow much now but it was just futureproofing


You may be calling me crazy but this is bothering me so much, like how did I look into every little detail and end up making this big of a mistake. Also, I am under the assumption that going to 3.21 will give me lower RPM's at 80mph, please correct me if I'm wrong.

Switch to taller tires

 

[Gary Dennis]

Did you think about having it tuned or buying a tuner? I would think spending $300-$400 and gaining 2-4 mpg's would be the cost efficient way to go.

 

[RAM_CHAOS]

Out of curiosity- has anyone had any good luck with the EcoDiesel? I almost bought one but couldn’t find a single good review past 50k miles. Basically the engine fails apart and people start finding metal shavings in the oil filter…….

 

[Zoe Saldana]

Just posted in another reply above if you want to take a glance

I can't follow that.

Here is what it should look like

Old​	​	​	​	​
Miles per Yr​	MPG​	Gallons​	Cost/gal​	Cost/yr​
12000​	30​	400​	5​	2000​
New​	​	​	​	​
Miles per Yr​	MPG​	Gallons​	Cost/gal​	Cost/yr​
12000​	32​	375​	5​	1875​
​	​	​	​	​
​	​	Savings/year​	​	125​
​	​	​	​	​
​	​	Cost of gear change​	​	5000​
​	​	​	​	​
​	​	Years to break even​	​	40​

 

[aj_g]

Holy sh** (cow). I’ve done a lot of axle overhauls, gear swaps, mods and repairs. That’s probably one of the highest quotes I’ve seen for a gear swap. Take it to a driveline specialist and get it done right. $2750 total is a good price for a 4x4. Not including labor? It’s all labor.

Technically this quote was from their own driveline specialist, was sent quote for parts - he'd rather replace the entire front axel whole

Qty Part Number Location On Hand List Price Sale Price Total
=== ================== ======== ======= ========== ========== ==========
1 68507252AB 0 1610.00 1610.00 1610.00
AXLE-FRONT COMPLETE
1 68056356AA AG4 2 37.61 37.61 37.61
SEAL-DRIVE PINION
1 68340289AA M204 0 100.22 100.22 100.22
BRG KIT-DRIVE PINION
1 3507678 M124 2 15.56 15.56 15.56
SPACER-DRIVE PINION BEARING
1 68340261AB M204 1 145.52 145.52 145.52
BRG KIT-DRIVE PINION
2 68340251AA M204 0 140.17 140.17 280.34
BRG KIT-DIFFERENTIAL SIDE
1 68477673AA 0 354.64 354.64 354.64
GEAR KIT-RING AND PINION

 

[aj_g]

Out of curiosity- has anyone had any good luck with the EcoDiesel? I almost bought one but couldn’t find a single good review past 50k miles. Basically the engine fails apart and people start finding metal shavings in the oil filter…….

Interesting
My brother in law has a gen2 one at 100k+ miles now
We had a gen2 one as well for like 60k miles as well iirc before we solid it off last year

 

[aj_g]

I have a 2022 Limited with 3.0eco diesel. 3.92 rear axle. I get an average of 28mpg. That's combined freeway, highway, and city driving. Granted, I don't drive 80, usually 77 on the freeway and 59 on the highway. RPM under 2,000.

How on earth wtf
Have you done any tuning?
I have same exact thing as you except it's Longhorn instead of Limited.
Do you have a tonneau cover or bigger tires? I just have the stock stuff with no cover

 

[tonynap]

No offense, but let's be honest.

By your own estimates, you achieve 35% mileage improvement slowing down to 70 MPH.

The cost of being cool (driving 80 MPH) is low mileage, lower intervals on fluid changes, brakes, rotors, suspension components, and lots of tires.

Save the 2,750 for those items.

 

[pkman]

aj-g - I'll swap axles with you! lol

 

[Marshall]

I don't know why you would think you can get 29 m/g at 80mph , don't matter what gear ratio you have, I have a 5.7 hemi, so can't comment on your motor, I have 3.92 gears and get great mileage, wind and hills make a large difference.
Of course your RPM will change if you change the gears, BUT how many miles will you have to drive to make up the cost of the change to maybe get a couple mpg more, and if you tow ,you will be upside down for sure

Just drive the truck and don't drive 80mph if you are that worried about your mileage.
If we drove that speed , up here we would spend lots of time in courts.

 

[CatDadAF]

The MPG difference between 80mph and 70 tells it all. Going to 3.21 is not going to get to 27mpg at 80. More likely 21mpg. And on anything other than a fairly long trip, the time saved isn't much. But, it's your money.

Considering I drive 60-65 around town and 70 on the highway, I'd be pretty tickled with 27+mpg instead of the 17-20 I get now.

It's funny, because just this morning driving to work on the toll road, I was doing 85mph, and I was getting 32mpg. I have a 22 limited, eco diesel with 3.21. And maybe the air suspension in aero mode helps as well.

 

[Bricknhank]

I like the advice to go test drive another truck with 3:21 before you drop a bunch of cash on anything. If you like the 3:21 ratio you could put a slightly larger tire on resulting in near exact 3:21 ratio at the wheel and gain a little lift out of it. Its just another option.

There are internet calculators you can use to determine the tire size needed.

With the 8 speed and 3:92s you can handle a very large increase in tire size, the needed increase is easily handled, especially at 20ft above sea level.

I don't think you made such a big mistake, I'm going 3:92 over 3:21 every time. (I do live in the upper atmosphere tho.)

A couple of observations. First, if the OP can find a truck like his with a 3.21 gear there must be more trucks in the lot than here in the Chicago area. Second, although larger tires will get him closer to the gear ratio that he desires it’s not going to help his mileage any. If the tires are very tall than maybe a lift will be necessary, also not helping his mileage.

 

[R1200GS]

Hi, I had ordered my RAM with 3.92 ratio as I only seemed to come across the good articles at that time in which I learned that it will have a higher resale value in the future, better for towing, etc. I did see some mention of a negligible difference in mpg but thought nothing of it as the sticker did not update on the MPG at all after I selected 3.92. I had even picked up the bigger diesel tank because I wanted to be able to go on long trips while dreaming about the 29mpg thats advertised lmao.

I live in California, almost everyone and their mother drives 80mph here on the highways and most drive even faster. I live in a fairly rural area, I have to drive on the highways a fair bit in order to get most things.
In my first few weeks of testing, here's what I've noticed for mpg
80mph = 2200 rpm and ~20mpg
75mph = Just over 2000 rpm and ~24mpg
70mph = I dont remember the exact rpm but its 27+mpg

I did reach out to the service department at my local dealer and was told $2,750 + labor in order to switch to a 3.21 (guy sent me a detailed parts list as for the breakdown) and I'm following up with them now to see how much labor that would be.

In terms of switching over
Pros:
For the most part I can drive as I normally do and not have to worry about being inefficient in terms of diesel
Would be saving time as well as I'd be driving at 80mph instead of 70/75

Cons:
The upfront cost of course
Potential resale value in the future may be impacted but I dont like switching cars very often
Towing impact, I dont tow much now but it was just futureproofing


You may be calling me crazy but this is bothering me so much, like how did I look into every little detail and end up making this big of a mistake. Also, I am under the assumption that going to 3.21 will give me lower RPM's at 80mph, please correct me if I'm wrong.

IMHO the 3.92 is superior to the 3.21. The 3.92 I believe, ‘fits’ the nature of the 8 speed much much better than the 3.21. The Hemi is happier as well. The 3.21 may turn better mpg in some situations but the 3.92 makes the truck happier mechanically and systemically. If you have 4WD a change in ratios will be needed in both differentials plus a myriad of other issues to address; if 2WD not do much of an issue.

Go to a dealer and test drive both. It won’t take you long to decide to wrap your arms around the 3.92.

 

[aj_g]

Did you think about having it tuned or buying a tuner? I would think spending $300-$400 and gaining 2-4 mpg's would be the cost efficient way to go.

I’m in California, I don’t think I can right?

 

[aj_g]

I don't know why you would think you can get 29 m/g at 80mph , don't matter what gear ratio you have, I have a 5.7 hemi, so can't comment on your motor, I have 3.92 gears and get great mileage, wind and hills make a large difference.
Of course your RPM will change if you change the gears, BUT how many miles will you have to drive to make up the cost of the change to maybe get a couple mpg more, and if you tow ,you will be upside down for sure

Just drive the truck and don't drive 80mph if you are that worried about your mileage.
If we drove that speed , up here we would spend lots of time in courts.

Do you see the responses from the others? Lol

 

[aj_g]

It's funny, because just this morning driving to work on the toll road, I was doing 85mph, and I was getting 32mpg. I have a 22 limited, eco diesel with 3.21. And maybe the air suspension in aero mode helps as well.

Well then lol

 

[Docwagon1776]

Just drive the truck and don't drive 80mph if you are that worried about your mileage.
If we drove that speed , up here we would spend lots of time in courts.

80mph is the posted speed limit in some states on the interstate. Texas being the one I'm most familiar with, lots of 80mph stretches. Posted limit around here is 70, but troopers don't bother you until 85+ unless you're weaving in and out or otherwise being as ******.

 

[scott lass 18]

Hi, I had ordered my RAM with 3.92 ratio as I only seemed to come across the good articles at that time in which I learned that it will have a higher resale value in the future, better for towing, etc. I did see some mention of a negligible difference in mpg but thought nothing of it as the sticker did not update on the MPG at all after I selected 3.92. I had even picked up the bigger diesel tank because I wanted to be able to go on long trips while dreaming about the 29mpg thats advertised lmao.

I live in California, almost everyone and their mother drives 80mph here on the highways and most drive even faster. I live in a fairly rural area, I have to drive on the highways a fair bit in order to get most things.
In my first few weeks of testing, here's what I've noticed for mpg
80mph = 2200 rpm and ~20mpg
75mph = Just over 2000 rpm and ~24mpg
70mph = I dont remember the exact rpm but its 27+mpg

I did reach out to the service department at my local dealer and was told $2,750 + labor in order to switch to a 3.21 (guy sent me a detailed parts list as for the breakdown) and I'm following up with them now to see how much labor that would be.

In terms of switching over
Pros:
For the most part I can drive as I normally do and not have to worry about being inefficient in terms of diesel
Would be saving time as well as I'd be driving at 80mph instead of 70/75

Cons:
The upfront cost of course
Potential resale value in the future may be impacted but I dont like switching cars very often
Towing impact, I dont tow much now but it was just futureproofing


You may be calling me crazy but this is bothering me so much, like how did I look into every little detail and end up making this big of a mistake. Also, I am under the assumption that going to 3.21 will give me lower RPM's at 80mph, please correct me if I'm wrong.

Don’t wast your money. Had a 3.21. In truck went to a 3.92. Best thing ever did. Lost 1 mpg that’s it . Use your money for gas instead ok ! Ran great on freeway no problem s. And soooo much better going uphill on mountains too !

 

[CheechDogg.0n37s]

Don’t wast your money. Had a 3.21. In truck went to a 3.92. Best thing ever did. Lost 1 mpg that’s it . Use your money for gas instead ok ! Ran great on freeway no problem s. And soooo much better going uphill on mountains too !

I wouldn't waste my money going back down to 3.21s either lol ... but looks like he's pretty dead set on doing so, it's like $100 to get your choice of gears when you order a truck compared to $2k + to do it outside, unless he really needed it to say tow or to compensate for bigger wheels and tires it just doesn't make any sense to spend the money lol .. but hey it's his money lol