3.21 vs 3.92: The Last Word

[cj7]

So, I’ve read all the posts here related to the 3.21 vs 3.92, but now have back-to-back, real world experience with both. Here’s the result:

Buy the 3.92 if:
- you are going to tow more than 8,000 lbs
- you are going to put big tires on
- you need a rock-crawling 1st gear
- you really don’t care how much you spend on gas
- you just have to have the 3.92, for rational or other reasons

If none of the above, buy the 3.21. I just spent a week and 600 mi with a brand new 2020 1500 DT Laramie 5.7 non-etorque 3.21 and the the next 600mi week with same brand new truck but e-torque 3.92 (that I had ordered a month earlier).

As for the usual reasons to buy a 3.92:
- acceleration: yes the 3.92 is a little more perky feeling, but the 3.21 is plenty quick. In fact, the 3.92 1st gear is so low,you’ll be well into 3rd before you hit 60. The 3.21 hits 60 right after shifting into 3rd.
- towing: for trailers at or under 8k, the 3.21 is fine. Yes it will operate one one gear lower pretty much the whole time, and be a little slower from a stop, but easily plenty of power.
- load capacity: no difference, so not a factor

I ordered and took delivery of the 3.92, and while it’s fine, had I ordered after having the 3.21, I probably would have gone 3.21. My travel trailer is around 6300#, and either works.

MPG wise, the 3.21 averaged almost 2 mpg better. I do 80/20 highway/city by miles, but 50/50 by time, and the 3.92 mileage is notably worse at stop&go and at speeds over 70. (should note the 3.92 truck was a couple hundred pounds heavier). The 3.92 turns 1980 RPM at 70, while the 3.21 does 1620. Excluding towing, I’m averaging 18 in the 3.92 etorque so far.

That all said, the 3.92 should be a tiny bit easier to sell, as it can do everything (except get better mileage). while some buyers will avoid 3.21 trucks.

Also, the 3.21 truck downshifts from 8th much more readily, and seems to come out of ECO more readily. (working on another info post, on reverse engineering the criteria for entering/exiting ECO).

Side note, I like the eTorque, and am not bothered by ECO or Stop-Start. I would definitely buy etorque again.

Anyhow, I quite like my truck so far, and am not trading it for a 3.21, but figured I’d pass on these observations for those considering their options.

 

[TBass]

I apprecaite your perspective. I wonder if you would feel the same if you lived at 5000 feet of elevation and frequently went in to the mountains. I was torn on which to order & ulitmately went with the 3.92 due to the frequency in which I head to the high country.

Thanks for your thoughts!

 

[Gen3CoupeTX]

Now we all know that isn't going to be the last word on this topic ... Nice try though! I had no rational reason for insisting on 3.92, other than it's what I wanted. If I couldn't get a 392 engine, I'd at least have that number in the rear. Us old timers will remember when gears like 4.11 were almost out of the question for highway driven vehicles. Times changed for the better on this!

 

[Dusty1948]

Anyone that's ever be married will tell you there's no such thing as "the last word," but I'll share my opinion.

I had two 4th gens (DS) with the 3.92 diff and now a 3.21 on my '19. Since I no longer have a 9600 pound towing need, I ordered this DT with the 3.21.

With the eight speed I'd see normal 1-2 shifts at 5 to 6 MPH with the 3.92. It was pretty fast off the line, but during the winter it was hard to prevent wheel spin even with 20 inch snow tires and limited slip.

My 2019 really shifts much smoother and my seat of the pants feel says that in the average traffic speeds the acceleration is just as good and maybe even better. I can still tow 7600 lbs. if I need to. My gas mileage is averaging just under 2 MPG better than my 2014.

Best regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 17 July 2018. Now at: 030019 miles.

 

[Richard320]

Us old timers will remember when gears like 4.11 were almost out of the question for highway driven vehicles. Times changed for the better on this!

Amen to that.

I still have a Wrangler with 4.10 gears and a 5 speed, and on the freeway I'm always reaching for the next gear that isn't there.

 

[silver billet]

The last word IMHO: the 3.92 is not worth it (with the exception being for those living in mountainous areas)

I spin tires taking off already (especially on rural/dirty roads while turning a corner).
Every day I use the 8th gear with 3.21, often sustained for 10+ km.

The only benefit the 3.92 has is for pulling a trailer > 8000 pounds. But if you do the math; 8000 pounds = approx 900 pounds tongue weight, add another 400 - 500 pounds for family + luggage and you are already at max payload for the upper trims.

So buy a 2500 if you need the 3.92

 

[Dusty1948]

The last word IMHO: the 3.92 is not worth it (with the exception being for those living in mountainous areas)

I spin tires taking off already (especially on rural/dirty roads while turning a corner).
Every day I use the 8th gear with 3.21, often sustained for 10+ km.

The only benefit the 3.92 has is for pulling a trailer > 8000 pounds. But if you do the math; 8000 pounds = approx 900 pounds tongue weight, add another 400 - 500 pounds for family + luggage and you are already at max payload for the upper trims.

So buy a 2500 if you need the 3.92

Don't forget the revs per mile difference.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33 gallon fuel tank, factory dual exhaust, 18” wheels. Build date: 17 July 2018. Now at: 030019 miles.

 

[rudyyoko]

Now we all know that isn't going to be the last word on this topic ... Nice try though! I had no rational reason for insisting on 3.92, other than it's what I wanted. If I couldn't get a 392 engine, I'd at least have that number in the rear. Us old timers will remember when gears like 4.11 were almost out of the question for highway driven vehicles. Times changed for the better on this!

In the 80s when I was pulling a 24ft 4 horse trailer, 4.11s was the only gears I wanted on my truck. I have never gone faster than 60mph with any trailer that was heavier than 6k pounds. 90% of the time I was pulling these horse trailers was for camping in the mountains.

 

[Willwork4truck]

“The Last Word” on this debate will be when they don't make the gears anymore. Nothing else will shut down people’s questions or opinions about them.
i continue to wish for 3.55’s with a hemi In the 5th gen.

 

[WXman]

I wouldn't accept anything on my new truck except the 3.92 gears. In my experience, numerically higher gears give better performance and MPG in town, tow trailers better, and are less stressful on the engine/trans. The ONLY time the 3.92s will hurt is while on interstate trips at long distances. So, to me it was a no-brainer for $95 bucks.

 

[Hamdizle]

3.92 4 life.....more capability is always better then less imo. I do tow as well. The marginal difference in gas doesn't matter to me. My 2012 has 3.21 and I dont get any better than 17.5 on the highway.

 

[Patsy1099]

Wait, isn’t spinning the rear wheels whenever possible a good thing

 

[barr0208]

The last word IMHO: the 3.92 is not worth it (with the exception being for those living in mountainous areas)

I spin tires taking off already (especially on rural/dirty roads while turning a corner).
Every day I use the 8th gear with 3.21, often sustained for 10+ km.

The only benefit the 3.92 has is for pulling a trailer > 8000 pounds. But if you do the math; 8000 pounds = approx 900 pounds tongue weight, add another 400 - 500 pounds for family + luggage and you are already at max payload for the upper trims.

So buy a 2500 if you need the 3.92

not on a 2500 only 3.73 available

 

[cj7]

I wouldn't accept anything on my new truck except the 3.92 gears. In my experience, numerically higher gears give better performance and MPG in town, tow trailers better, and are less stressful on the engine/trans. The ONLY time the 3.92s will hurt is while on interstate trips at long distances. So, to me it was a no-brainer for $95 bucks.

I also paid the $95, and think everyone is free to decide for themselves, but
- mileage in town AND at highway speeds is less (actual experience)
- 0-60 performance may be slightly better, but not much
- tows better, but under 8k and not in the mountains, not much difference
- no difference in stress on trans; they are rated on input power
These are the facts, but again, you get to pick for you.

 

[mississippi_clay]

So, I’ve read all the posts here related to the 3.21 vs 3.92, but now have back-to-back, real world experience with both. Here’s the result:

Buy the 3.92 if:
- you are going to tow more than 8,000 lbs
- you are going to put big tires on
- you need a rock-crawling 1st gear
- you really don’t care how much you spend on gas
- you just have to have the 3.92, for rational or other reasons

If none of the above, buy the 3.21. I just spent a week and 600 mi with a brand new 2020 1500 DT Laramie 5.7 non-etorque 3.21 and the the next 600mi week with same brand new truck but e-torque 3.92 (that I had ordered a month earlier).

As for the usual reasons to buy a 3.92:
- acceleration: yes the 3.92 is a little more perky feeling, but the 3.21 is plenty quick. In fact, the 3.92 1st gear is so low,you’ll be well into 3rd before you hit 60. The 3.21 hits 60 right after shifting into 3rd.
- towing: for trailers at or under 8k, the 3.21 is fine. Yes it will operate one one gear lower pretty much the whole time, and be a little slower from a stop, but easily plenty of power.
- load capacity: no difference, so not a factor

I ordered and took delivery of the 3.92, and while it’s fine, had I ordered after having the 3.21, I probably would have gone 3.21. My travel trailer is around 6300#, and either works.

MPG wise, the 3.21 averaged almost 2 mpg better. I do 80/20 highway/city by miles, but 50/50 by time, and the 3.92 mileage is notably worse at stop&go and at speeds over 70. (should note the 3.92 truck was a couple hundred pounds heavier). The 3.92 turns 1980 RPM at 70, while the 3.21 does 1620. Excluding towing, I’m averaging 18 in the 3.92 etorque so far.

That all said, the 3.92 should be a tiny bit easier to sell, as it can do everything (except get better mileage). while some buyers will avoid 3.21 trucks.

Also, the 3.21 truck downshifts from 8th much more readily, and seems to come out of ECO more readily. (working on another info post, on reverse engineering the criteria for entering/exiting ECO).

Side note, I like the eTorque, and am not bothered by ECO or Stop-Start. I would definitely buy etorque again.

Anyhow, I quite like my truck so far, and am not trading it for a 3.21, but figured I’d pass on these observations for those considering their options.

Excellent information! I’m in the used market now, and trying to decide if i “have” to have 3.92. I still prefer 3.92, but it isn’t going make or break my decision now. Thanks for the info

 

[Mountain Whiskey]

The last word is:

3.21 = Girlie Gears

3.92 = Truck Gears.

 

[djevox]

This isn’t the last word. You know what is? The bird. The bird is the word.

 

[theblet]

Yay! Another thread!!

 

[SnowBlaZR2]

How many of these are there?

 

[Ramroo]

Good info.
About what I was thinking also. I do a fair amount of interstate travel also, and like to see the rpms lower when I have my smash up.
I do like my girl truck. We can always sell our trucks to a girl when we want.