eTorque 5.7 and 3.92 limited slip

[Ortiz7983]

If you're turning around 2000 rpm at 70mph, you have the 3.92 axle.

So what does this mean?

 

[Zeronet]

So what does this mean?

3.21

 

[ExcursionDiesel]

So what does this mean?

3.21 axle. Better fuel economy at higher speeds. Less wear on the motor. Lower towing capacity and a little slower acceleration.

 

[768mph]

3.21 axle. Better fuel economy at higher speeds. Less wear on the motor. Lower towing capacity and a little slower acceleration.

3.92 is less wear on the motor; it doesn’t have to work as hard to move as the 3.21s do. Adding another 700rpm on the hwy won’t do the damage you’re referring to.

And my wife has a 19 Ram Big Horn Sport 3.21 and I have a Laramie 3.92, our hwy fuel mileage is nearly identical. As many others have proven time and again.

 

[ExcursionDiesel]

3.92 is less wear on the motor; it doesn’t have to work as hard to move as the 3.21s do. Adding another 700rpm on the hwy won’t do the damage you’re referring to.

And my wife has a 19 Ram Big Horn Sport 3.21 and I have a Laramie 3.92, our hwy fuel mileage is nearly identical. As many others have proven time and again.

Guessing you don't drive 80mph. My mileage on an 80 mile run to the airport was 16.8 at 80mph with my 3.92 equipped Limited 4x4. Are the 3.21 trucks that bad? Other threads I've read confirm that the 3.21 gets better mileage at interstate speeds. 22% higher engine speed is significant. There are components in the motor (like the cam) that aren't load dependent and are drsigned for a certain number of cycles. A 3.92 truck will reach the design limit sooner.

The consensus of articles support what I said. But the subject is like the Torque vs Horsepower argument held among people who can't define either one accurately. So, to each their own.

 

[768mph]

Guessing you don't drive 80mph. My mileage on an 80 mile run to the airport was 16.8 at 80mph with my 3.92 equipped Limited 4x4. Are the 3.21 trucks that bad? Other threads I've read confirm that the 3.21 gets better mileage at interstate speeds. 22% higher engine speed is significant. There are components in the motor (like the cam) that aren't load dependent and are drsigned for a certain number of cycles. A 3.92 truck will reach the design limit sooner.

The consensus of articles support what I said. But the subject is like the Torque vs Horsepower argument held among people who can't define either one accurately. So, to each their own.

Read what you said but slowly. Im
Sure Rams engineering put out lifecycle and maintenance cycles for the motor and it doesn’t differ between 3.21 or 3.92. It varies by heavy duty or light use. Not by gear ratio.

And no, I don’t drive 80 because it’s a brick on wheels. My old Charger 392, 73-75mph got me 25-27mpg. But that’s not a 5200lb brick on wheels.
I drive 70-72 in my truck.

And hwy estimating numbers are based off 65mph hwy driving through EPA. Driving most vehicles above that threshold will alter mileage.

You’re correct, to each their own. (Sincere)

 

[Gman]

MDS likely makes much more of a difference in highway MPG than the rear axle ratios.

 

[ExcursionDiesel]

EPA ratings have no bearing on this discussion. I'm not trying to meet EPA ratings at 80mph. I'm trying to catch a plane on time. My original assertion was that a higher axle ratio at "higher speeds" (which is above 65) has reduced economy. Many members here have reported 19mpg at 80mph with 3.21 and others with 3.92's have reported 17 or.less. That's a 10% difference. If a higher ratio has no negative affects, let's all run a a 3.92 axle! Better yet, lets lock the max gear to 7th and have at it. Same difference as 3.92 vs 3.21. Nobody would do that unless they are towing....which is the primary reason for the 3.92. I tow and am willing to accept the tradeoffs.

 

[768mph]

EPA ratings have no bearing on this discussion. I'm not trying to meet EPA ratings at 80mph. I'm trying to catch a plane on time. My original assertion was that a higher axle ratio at "higher speeds" (which is above 65) has reduced economy. Many members here have reported 19mpg at 80mph with 3.21 and others with 3.92's have reported 17 or.less. That's a 10% difference. If a higher ratio has no negative affects, let's all run a a 3.92 axle! Better yet, lets lock the max gear to 7th and have at it. Same difference as 3.92 vs 3.21. Nobody would do that unless they are towing....which is the primary reason for the 3.92. I tow and am willing to accept the tradeoffs.

If you’re arguing that at the same speed, the 3.21 gets better mileage than the 3.92, the yes. That would be common sense. Not sure that point has to be argued. There’s a clear difference at constant speed with no varible other than gear ratio.

I was referring to overall mileage. As in average. Because not one person is a straight highway driver unless you’re pushing a Peterbilt with a 12L Detroit.

While the 3.21 is on the highway and going up that hill, I’m still in 8th while they downshift.
While in town, im in MDS longer with the 3.21 is not.

If I’m running dead even with them on the highway at 80, and continue my trip. Yes, common sense would say, they will get better mileage at that time and that trip.

Catching a plane helps if you leave earlier and plan ahead.
Seriously. This is not to be argumentative, I was referring to some of us having better success with 3.92 rear than 3.21.

Btw, noticed your signature. Nice build.

 

[ExcursionDiesel]

If you’re arguing that at the same speed, the 3.21 gets better mileage than the 3.92, the yes. That would be common sense. Not sure that point has to be argued. There’s a clear difference at constant speed with no varible other than gear ratio.

I was referring to overall mileage. As in average. Because not one person is a straight highway driver unless you’re pushing a Peterbilt with a 12L Detroit.

While the 3.21 is on the highway and going up that hill, I’m still in 8th while they downshift.
While in town, im in MDS longer with the 3.21 is not.

If I’m running dead even with them on the highway at 80, and continue my trip. Yes, common sense would say, they will get better mileage at that time and that trip.

Catching a plane helps if you leave earlier and plan ahead.
Seriously. This is not to be argumentative, I was referring to some of us having better success with 3.92 rear than 3.21.

Btw, noticed your signature. Nice build.

I agree that driving conditions will favor one axle over another. That's exactly right. I used to live in the Mississippi Delta and there is not such thing as a hill and 90% of all my driving was rural 2 lane highway at 60-65mph. The 3.21 would have an advantage there. Now I live in a mildly hilly area in TN and my 3.92 truck will only downshift if my speed is too low or on the rare instance of a steep hill. Here, the advantage probably is a wash. In the mountains...3.92 for sure. I do drive into the nearby Delta for work and on flat ground, I can tell that the truck feels like it could easily cruise more economically in 9th gear...if it had one. I had to choose when I ordered mine and I went with the 3.92 due to the 4500 lb cargo trailer I tow on weekends....and because I wanted a truck that was more eager to go. I can live with the reduced economy. As far as engine wear goes, religiously changing the oil and proper maintanance probably have a greater affect!

Bottom line, the buyer must choose their axle ratio based on the application and accept the tradeoffs. There is no perfect choice!

Btw....80mph on I-40 in West TN is just going with the flow!

 

[768mph]

I agree that driving conditions will favor one axle over another. That's exactly right. I used to live in the Mississippi Delta and there is not such thing as a hill and 90% of all my driving was rural 2 lane highway at 60-65mph. The 3.21 would have an advantage there. Now I live in a mildly hilly area in TN and my 3.92 truck will only downshift if my speed is too low or on the rare instance of a steep hill. Here, the advantage probably is a wash. In the mountains...4.92 for sure. I do drive into the nearby Delta for work and on flat ground, I can tell that the truck feels like it could easily cruise more economically in 9th gear...if it had one. I had to choose when I ordered mine and I went with the 3.92 due to the 4500 lb cargo trailer I tow on weekends....and because I wanted a truck that was more eager to go. I can live with the reduced economy. As far as engine wear goes, religiously changing the oil and proper maintanance probably have a greater affect!

Bottom line, the buyer must choose their axle ratio based on the application and accept the tradeoffs. There is no perfect choice!

Well said Sir.

 

[Gman]

An article that pretty much covers the details: https://www.edmunds.com/car-buying/how-to-choose-the-right-axle-ratio-for-your-pickup-truck.html