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I’m looking to buy a 3rd Gen ED and noticed how many of the ones sitting on the lot are geared with 3.21 gears. Who likes this and who wishes they had the 3.92.

Jeff
 

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Well I can only say that 3:21's are good for about 5 grocery bags on flat land with no headwind. I have 3:55's and never tow heavy. I have a 16' basic aluminum boat, a 10' enclosed cargo trailer with one ATV and a 17' travel trailer. My last travel trailer was a 22' and none of the above cause any slow downs on the hills or fighting a stiff headwind although without BS'ing it can be felt.
 

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I have a 2014 with 3.55 and 37" 12 ply load F tires, and I tow a 8klb trailer with ease. You know its there, but I have plenty of power to move it. I am not a speed demon, however, and may tow slower then some (55-70 range depending on the trailer and conditions). The hottest my oil has been is 235 degrees this year towing that 8k lb trailer and up a steep grade (7% for over a mile). I was going about 55mph up it, which helped. I rent trailers and tow every week, sometimes every day. My smallest trailer is a 17' 3500lb single axle travel trailer and my biggest is my 8000lb 30ft 10 person sleeper travel trailer. (FYI, I am tuned and deleted which helps keep the temps down).

With the new cooling system, larger turbo, upgraded intake and more torque (60lbs more of it, plus 40hp), I think you would be able to tow just fine up to 8000-9000lbs. Seeing as the 3.92 is rated at 12,560 lbs, I would imagine 3000 lbs less for the 3.21 would be good, (depending on the trim level and options selected of course).
 

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Jeff. You pose a question but give no details behind it.

Where do you live? That is important as mountain driving is sure different from the flats of most Southern areas of the East. Then you get into your personal driving style. Short runs in the city verses long trips around the country and long runs on a daily commute. Each is different usage that would compromise some rear-end choices.

Towing and heavy loads is maybe the most important issue you have ignored to supply. If you do not tow often or much or far then a towing rear end ratio is a bit foolish, unless you like to drag race from a stop.

There is no good answer to cover your needs as you have not revealed your usage and needs. Do that and responses can be more informative.
 

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You certain you’re not looking at the default and not upgrades. Everything I looked at earlier this year had the 3.92 upgrade in Ecodiesel. It’s what I have as well.

it’s a $95 feature BTW
 

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Well I can only say that 3:21's are good for about 5 grocery bags on flat land with no headwind. I have 3:55's and never tow heavy. I have a 16' basic aluminum boat, a 10' enclosed cargo trailer with one ATV and a 17' travel trailer. My last travel trailer was a 22' and none of the above cause any slow downs on the hills or fighting a stiff headwind although without BS'ing it can be felt.
Ok, I agree that 3.55's will tow and handle heavy loads better than 3.21's, but this above ^^^ is a bit extreme.

The first diesel in our family was a 1978 GMC 5.7 in a 2wd half ton, with 2.73's and my dad hauled his trailer to Florida every year for many years with that truck. In fact ... all he used that truck for was for holidays, half of them towing, and when it finally died of a broken crankshaft (a common issue with them), it had over 100,000km on it. He was hauling a 24' Terry Taurus.

Depending on your intended usage, your truck configuration, your driving attitude, etc ..... you may find that 3.21's are just fine for you. As Capt said .... you were short on info.
 

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On the 2020 Gen 3 EcoDiesels, 3.21 is standard. 3.92 is a $95 option. I searched until I found a 3.92 equipped truck. It was built in November and I brought it home in February.

The reasons I wanted 3.92:

Tows better
Better MPG in town
Handles larger tires better
Better resale
Slightly less transmission shifting
 

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I’m looking to buy a 3rd Gen ED and noticed how many of the ones sitting on the lot are geared with 3.21 gears. Who likes this and who wishes they had the 3.92.

Jeff
lots of info needed, but to be honest it really boils down to this, if you need or even possibly foresee a reason to need max towing based on what truck configuration (most important) you want, the 3.92 is a must.

I had the 3.21 in my 2016 EcoD crew cab, and loved it no issues on highway hills, mountains, flats, just set the cruise and go and let the truck do its thing.

now with my 2020 I have the 3.92 I don’t really notice any difference, might have a little more pep but fuel and range have been on par or better than the 2016, but now i can tow up to 9500lbs and that is something the 3.21 can’t do.

Whatever choice you go with B committed to it because it’s too expensive to change it after the fact
 

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Like others have stated, get the 3.92 if you are going to do any type of pulling/carrying loads. In fact, I would get it no matter what unless you aren't using this as a truck. So easy to just pay for it now rather than try to re-do it later. We have a camper on ours w/ 3.92 and not a single issue passing, climbing, etc. hills/cars/etc.
 

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I’m looking to buy a 3rd Gen ED and noticed how many of the ones sitting on the lot are geared with 3.21 gears. Who likes this and who wishes they had the 3.92.

Jeff
We have a 2015 ED and drove trucks with both 3.21 and 3.92 gears when shopping. We were transitioning from a '07 6.7 dually with 3.73 gears and the ED with the 3.92's felt more responsive than the 3.21's. We tow a two horse dressing room horse trailer with two horses, total weight about 6K. The truck gets 18MPG towing and handles the Georgia hills just fine. Best mileage we ever achieved was 28MPG manually calculated on a trip to PA from GA. We never drove below 70MPH on the highway.
 

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You won't see much of a difference towing the "rated" load with either ratio.

If you do the math you will see the 3.21 tows in 7th gear with tow/haul and the overall ratio/rpms are nearly identical to the 3.92 in 8th gear. Likewise, for 3.21 gears 5-6 and 3.92 gears 6-7. The major difference is in gears 1-3 and after that the 3.21 is one gear lower to match the overall pulling torque.

Since the diesel engine makes power lower in the rpm band taking off isn't an issue with the 3.21s as the truck will spin the rear tires on a hill even with the truck at full rated load. The issue is protecting the drive line as the drive line torque load is around 20% higher with the 3.21 for the same trailer weight.

The new generation truck has smaller tires so a direct ratio comparison isn't fair when stock. The new truck effective 3.21 ratio is around 3.4 and the effective 3.92 ratio is now slightly over 4.0 when comparing to the previous Eco. This coupled with the 400 rpm lower power band changes the game compared to the 3.55 previous Eco. The transmission has been reprogrammed to not downshift to near red-line as well.

The new truck tows nothing like the previous one. I have a 2020 with 3.21s and had a 2016 with 3.55s and there is no comparison. They seemed to have solved the high coolant temp issue but the oil temperature still seems higher than I would like towing 7,200 lbs (around 240 degrees) at 75 degrees ambient in the mountains.

With the truck unloaded the rpms are around 1600 at 70 mps which is in the full torque band. The 3.92 is around 2000 which is too high for me. A 3.21 truck can simulate the 3.92 on the highway by manually shifting to 7th. The engine noise picks up and it seems to be turning too fast.

If you are going to put larger tires on the truck or tow over what the 3.21 is rated for (I think mine is around 7,900 lbs for a Longhorn, crew, 4x4, long bed) then I would definitely go with the 3.92s. You will definitely loose a little refinement on the highway with the 3.92s.
 

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You won't see much of a difference towing the "rated" load with either ratio.

If you do the math you will see the 3.21 tows in 7th gear with tow/haul and the overall ratio/rpms are nearly identical to the 3.92 in 8th gear. Likewise, for 3.21 gears 5-6 and 3.92 gears 6-7. The major difference is in gears 1-3 and after that the 3.21 is one gear lower to match the overall pulling torque.
All y'all gear ratio math junkies should get your stories straight...
So the 8HP75 transmission is cable of making up .71 gear ratio difference where as the 8HP70 is only capable of making up the .37 difference in gear ratio going from 8th down to 7th when the difference between the two transmissions is about .1 difference? It was touted hot and heavy the 3.55 in 7th is the same as 3.92 in 8th...and now it's the same 3.21 in 7th?
The horsepower/torque is the same at the business end(output shaft) of the transmission regardless of what axle ratio is in the truck
Pick how you want to look at this way:
3.21 is the baseline and you have 20% more torque overall with 3.92
3.92 is the baseline and you have 20% less torque with 3.21
 

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The math is correct and you are correct if both the 3.21 and 3.92 are in the same gear. If the 3.21 is down one gear they are the same in gears 3-7 (3.21) or 4-8 (3.92). I don't understand your point.
 

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The math is correct and you are correct if both the 3.21 and 3.92 are in the same gear. If the 3.21 is down one gear they are the same in gears 3-7 (3.21) or 4-8 (3.92). I don't understand your point.
It was touted hot and heavy the 3.55 in 7th is the same as 3.92 in 8th...and now it's the same 3.21 in 7th?
There is only a .1 difference between the 8HP70 and 8HP75 7th gear ratios yet somehow your math has 7th gear making up for 3.21 where as the 8HP70 could only make up for 3.55..
Maybe @howie12 can explain this madness as he has all the charts and graphs to prove one of you two wrong. We should tag in @Bounty Hunter as he loves a good a̶r̶g̶u̶m̶e̶n̶t̶ debate about this too..
 

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Well I can only say that 3:21's are good for about 5 grocery bags on flat land with no headwind. I have 3:55's and never tow heavy. I have a 16' basic aluminum boat, a 10' enclosed cargo trailer with one ATV and a 17' travel trailer. My last travel trailer was a 22' and none of the above cause any slow downs on the hills or fighting a stiff headwind although without BS'ing it can be felt.
I have 3.21s and have had no trouble towing regardless of conditions.
 

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There's a reason the 3.92 gear is a $95 option and is one of the most frequently selected options on the order sheet.

Also, my 8th is not your 7th.

Gear x3.21 x3.92
5.00 16.05 19.60
3.20 10.27 12.54
2.14 6.87 8.39
1.72 5.52 6.74
1.31 4.20 5.14
1.00 3.21 3.92
0.82 2.63 3.21
0.64 2.05 2.51

As you can see there isn't one single place anywhere in the entire gear spread (except 1:1 drive obviously 6th gear w/ 3.21 vs. 7th w/ 3.92) where the two axle ratios overlap. But, the 3.92 will be able to hold 8th far easier on the interstate, while still turning less RPM than 7th gear with 3.21 axle gears would. So, the 3.92 is better everywhere from 0 to 80 miles per hour.

I favor the 3.92 because it takes off easier, accelerates easier, cruises in town easier, and stays in 8th gear on the highway more often. This, in turn, actually improves MPG everywhere except the interstate.
 
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Your chart shows that 3.92 in 7th is exactly the same as the 3.21 in 6th. The .1 difference between 7 /8 isn’t significant. Of course it isn’t a 100 % match but very close until the lower gears as I originally stated.

I haven’t read any issues from the 2020 Eco 3.21 owners and most negative comments come from people that haven’t towed with the 2020 Eco 3.21.

I will say that Ram totally messed up the cruise control operation when towing in hilly areas. It really is no better than the prior model. It tries to hold speed to the exact mph and will use full throttle to do so when it isn’t needed. I wish we had full manual gear selection for the transmission. My guess is there is still a week point somewhere in the engine or driveline for full manual control.

If I had to put up with the noise from the 3.92 on the highway when the truck is unloaded I would have went another engine, truck size, or brand. For me the 2020 Eco 3.92 makes too much noise and vibration unloaded on the highway in 8th spinning at 2000 rpm. With the 3.21 the engine is silent at 70. It is good we have an option.
 

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I favor the 3.92 because it takes off easier, accelerates easier, cruises in town easier, and stays in 8th gear on the highway more often. This, in turn, actually improves MPG everywhere except the interstate.
Real strong argument to justify your purchase, but saying the 3.92 improves MPG everywhere but open interstate just isn't accurate.

Looking at the above final drive ratio chart, I'd probably choose the 3.21 as well. Running one gear lower there's a slight mechanical advantage over the 3.92 truck. I tow heavy and I'm in no hurry in first gear, so that's a non-issue. Never use OD gears when towing so another non-issue. 3.21 for the all-around win.
 
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