3.92 with the Ecodiesel

[silver billet]

I totally agree with you about the 3.92 rear axle ratio having the advantage for towing, its the same transmission with either rear axle ratio.
You are correct by saying the bearings would heat up in the rear end, but most of the heat is generated by the crown and pinion friction.
Axles with higher ratios require less effort to turn the pinion drive gear, but requires more revolutions.
The transmission requires less effort in this application but the engine will be at a higher rpm, so it is a win win situation for towing frequently, less effort for the transmission and less effort for the rear axles, both will run cooler and will outlast the harder working systems.

Someone had commented earlier about racing going up a hill while towing, it doesn’t really matter how fast you make it up the hill, the hill is the same with either axle ratios, the advantage is with the 3.92 rear because the transmission will shift all the way up to the 8th gear with less effort and will get to the 8th gear sooner than with the 3.21.
So if you race or if you take it easy going up the same hill it will require less effort, create less heat and use less gas/fuel with the 3.92.

The 3.92 has the advantage for city driving, less effort to get the truck moving at every stop or red light, the only advantage for the 3.21 is for highway driving while not towing and not having bigger wheels.

I have been driving trucks and towing for 4 decades, the transmissions have come a long way, my first was a 5 speed manual. I really like my Rebel with the small displacement diesel, most of my driving does not require towing and my loaded trailers are less than the max towing capacity. It’s hard to believe that my truck gets to 4th gear by the time it reaches the end of my driveway

Again; the 3.92 gets you off the line slightly quicker. That's it. Once the 3.21 is in third; whatever that speed is, at that point/speed BOTH trucks have approximiately equal remaining gear ratios left, they will shift their remaining shifts at approx the same time, and will accelerate the remaining distance nose to nose. This is the crux of the (one half of the) argument and what most people aren't appreciating. (The other half of the argument of course is that these trucks can't really utilize the 3.92 for the vast majority of people because of available payload and suspension issues and how light the truck is.)

 

[Rebelguy2020]

Again; the 3.92 gets you off the line slightly quicker. That's it. Once the 3.21 is in third; whatever that speed is, at that point/speed BOTH trucks have approximiately equal remaining gear ratios left, they will shift their remaining shifts at approx the same time, and will accelerate the remaining distance nose to nose. This is the crux of the (one half of the) argument and what most people aren't appreciating. (The other half of the argument of course is that these trucks can't really utilize the 3.92 for the vast majority of people because of available payload and suspension issues and how light the truck is.)

This is the simplest way to explain it.

The 8 speed transmission is the same on all 1500. The output shaft from the transmission will turn at different ratios for each gear.

The difference is the rear axle ratio.

So in 1st gear with the 3.92 it requires less effort to turn the axle than the 3.21
Then the same thing repeats for all the remaining gears.

Of course if you have two identical trucks side by side going at the same speed in 8th gear, the truck with the 3.21 will have lower RPMs than the truck with the 3.92.

 

[silver billet]

This is the simplest way to explain it.

The 8 speed transmission is the same on all 1500. The output shaft from the transmission will turn at different ratios for each gear.

The difference is the rear axle ratio.

So in 1st gear with the 3.92 it requires less effort to turn the axle than the 3.21
Then the same thing repeats for all the remaining gears.

Of course if you have two identical trucks side by side going at the same speed in 8th gear, the truck with the 3.21 will have lower RPMs than the truck with the 3.92.

Again, common mistake. You're assuming both trucks are in the same numerical gear at the same speed. They won't be. They will be in the same "gear ratio", not the same numerical gear.

The 3.21 will be in 6th (with a gear ratio of 3.21), and the 3.92 will be in 7th (with a gear ratio of 3.2144). Note how though they're in different gears, they actually have an approximately equal gear ratio; meaning, they will have the same rpm at the same speed.

 

[VernDiesel]

Another interesting discussion on this.

2015 Pentastar V6 Towing [SUPERCHARGER SUCCESS!]

My wife recently inherited a 2015 RAM 1500 3.6L V6 2WD with 3.21 rear end (9k miles). We also have a 22ft 4600lb travel trailer. When it is fully loaded with cargo and people - we are right at the sticker limits of towing and GVWR. Legal, but barely. As anyone can guess, this is fine at sea...

www.ramforum.com

 

[Pristine1]

Again, common mistake. You're assuming both trucks are in the same numerical gear at the same speed. They won't be. They will be in the same "gear ratio", not the same numerical gear.

The 3.21 will be in 6th (with a gear ratio of 3.21), and the 3.92 will be in 7th (with a gear ratio of 3.2144). Note how though they're in different gears, they actually have an approximately equal gear ratio; meaning, they will have the same rpm at the same speed.

Again.... proving the 3.92 superior because it will always be one step ahead. You keep reverting back to cruising speed and not accelerating which is where the advantage still is with the 3.92 under load. It’s funny because I’ve agreed with you awhile back about being at cruising speed and the 8 speed being able to replicate similar ratios as the 3.92’s. For some reason you’re stuck on explaining the same thing over and over.

 

[Pristine1]

You're argument style is best described as .... "come at me bro!!" I have little respect or time for people that argue like you, and considering your very new account here, and your obvious intent to "yell" and not listen, well, I got better things to do with my time. (And NOBODY said anything about larger tires, don't move the goal posts). But anyway:

Couple key points here: the ZF 8 speed with 3.21 absolutely dominates every 6 speed I've done the math for, including the Toyota Tundra and 4 variants used by Ram heavy duty trucks (the RFE's and the Aisins).

Example:
first gear ratio with 3.21 is 16.05
first gear ratio with Aisin AS68RC and 4.44 is 16.65 (so slight win for the Aisin, but remember the ZF has 2 extra gears so as it's upshifting it will have closer ratios)

Yes that's right. You need a 4.44 just to MATCH the first gear ratio available with the 3.21 8 speed. And then the 8 speed still has extra gears.

What about the RFE's?
first gear ratio with 65RFE and 4.44 is 13.32
first gear ratio with 65RFE and 4.89 is 14.67

Yeah. The 3.21 ZF has a much higher gear ratio than the 6 speed with a 4.89

Next time do the math before posting. And feel free to make all the assumptions you like about my towing history, I'm quite amused.

5500’s only come with Aisin’s brosifff... Not sure why you’re so stuck on first gear and every gear ahead of a competing ratio. Apples to oranges everytime!

Don’t get all bent because I don’t agree with you. I’ve been having fun. You’re taking this too seriously. I wasn’t typing in all caps so I don’t believe I was yelling. Problem is you’re bothered by any logic other than what you read online. The fact is you’re ignoring anything that doesn’t fit your prerogative. Hey where’s my friend who agrees with me!? I’ve some what agreed with you on your own argument at the beginning and you’re still trying argue that same point about the other side of the equation. I’ve mentioned larger tires 2x at least and so have others. You have very selective comprehension. You only hear the parts you want to argue and still haven’t brought anything new to the table in all of this conversating.

Anything new to add??

I’ve yet to hear you state your extensive towing back ground or your real life experience. What do you tow? How many different vehicles have you towed with? How many decades are under your belt with real life experience towing your jet skis . I’m just kidding that was a low blow. I’m in all honesty just razzing you. Don’t take it seriously

 

[silver billet]

Again, common mistake. You're assuming both trucks are in the same numerical gear at the same speed. They won't be. They will be in the same "gear ratio", not the same numerical gear.

Again.... proving the 3.92 superior because it will always be one step ahead. You keep reverting back to cruising speed and not accelerating which is where the advantage still is with the 3.92 under load. It’s funny because I’ve agreed with you awhile back about being at cruising speed and the 8 speed being able to replicate similar ratios as the 3.92’s. For some reason you’re stuck on explaining the same thing over and over.

You keep on talking about "always one step ahead". This shows to me you didn't/don't really understand the issue. "one numerical gear ahead", yes. But it's an irrelevant observation and there is no need to fixate on it because they are in the same gear ratio. Gear ratios are the important metric, not the label it has (1, 2, 3 etc).

That has been my point the entire time. Third gear and up on the 3.21, no difference for pulling a trailer. This holds true either under acceleration, or just holding speed.

 

[silver billet]

5500’s only come with Aisin’s brosifff... Not sure why you’re so stuck on first gear and every gear ahead of a competing ratio. Apples to oranges everytime!

Don’t get all bent because I don’t agree with you. I’ve been having fun. You’re taking this too seriously. I wasn’t typing in all caps so I don’t believe I was yelling. Problem is you’re bothered by any logic other than what you read online. The fact is you’re ignoring anything that doesn’t fit your prerogative. Hey where’s my friend who agrees with me!? I’ve some what agreed with you on your own argument at the beginning and you’re still trying argue that same point about the other side of the equation. I’ve mentioned larger tires 2x at least and so have others. You have very selective comprehension. You only hear the parts you want to argue and still haven’t brought anything new to the table in all of this conversating.

Anything new to add??

I’ve yet to hear you state your extensive towing back ground or your real life experience. What do you tow? How many different vehicles have you towed with? How many decades are under your belt with real life experience towing your jet skis . I’m just kidding that was a low blow. I’m in all honesty just razzing you. Don’t take it seriously

Nice try. You back pedal any harder you'll break an ankle.

 

[Pristine1]

I totally agree with you about the 3.92 rear axle ratio having the advantage for towing, its the same transmission with either rear axle ratio.
You are correct by saying the bearings would heat up in the rear end, but most of the heat is generated by the crown and pinion friction.
Axles with higher ratios require less effort to turn the pinion drive gear, but requires more revolutions.
The transmission requires less effort in this application but the engine will be at a higher rpm, so it is a win win situation for towing frequently, less effort for the transmission and less effort for the rear axles, both will run cooler and will outlast the harder working systems.

Someone had commented earlier about racing going up a hill while towing, it doesn’t really matter how fast you make it up the hill, the hill is the same with either axle ratios, the advantage is with the 3.92 rear because the transmission will shift all the way up to the 8th gear with less effort and will get to the 8th gear sooner than with the 3.21.
So if you race or if you take it easy going up the same hill it will require less effort, create less heat and use less gas/fuel with the 3.92.

The 3.92 has the advantage for city driving, less effort to get the truck moving at every stop or red light, the only advantage for the 3.21 is for highway driving while not towing and not having bigger wheels.

I have been driving trucks and towing for 4 decades, the transmissions have come a long way, my first was a 5 speed manual. I really like my Rebel with the small displacement diesel, most of my driving does not require towing and my loaded trailers are less than the max towing capacity. It’s hard to believe that my truck gets to 4th gear by the time it reaches the end of my driveway

You are here for the win! What do you win? Life! Real life experience prevails wise one. I agree with all of what you put down and it is the same things I have learned over the last couple decades.
The heat is a big factor people ignore too and do not understand the underlining causes. It’s nice to see someone who knows this as well as you do because it is rare. You have to learn the hard way sometimes like burning up a rear end but the key is, we learn more about the cause and effects.

If Chrysler is still using the same 9.25 my gear guy had said it was prone to this gear failure. Not enough lubrication for the bearings when they get hot. Also may be the new age gear ratios trying to squeak out mpg before they had transmissions that would support these 3.21’s. Ask someone before the 8 speed about how great 3.21’s were for towing up the mountains. Those were the only customers who hated their Rams back then and swore the Hemi towed like crap.

 

[Pristine1]

Nice try. You back pedal any harder you'll break an ankle.

Back peddle, please give me an example of where I back peddled. I’ll wait....

 

[Pristine1]

You keep on talking about "always one step ahead". This shows to me you didn't/don't really understand the issue. "one numerical gear ahead", yes. But it's an irrelevant observation and there is no need to fixate on it because they are in the same gear ratio. Gear ratios are the important metric, not the label it has (1, 2, 3 etc).

That has been my point the entire time. Third gear and up on the 3.21, no difference for pulling a trailer. This holds true either under acceleration, or just holding speed.

Your argument is always that. Comparing 2-3, 3-4 and so on. You’ve done it over and over and over and over. These 3.21’s sound magical. Always winning one gear behind. I think I’ll re gear my truck went it arrives next week so I can tote my trailer one gear behind while overheating my drivetrain. Move on from the same point you’re trying to prove. It’s been discussed. We get it.

Oh and for the 10th time do you even tow anything? At this point I’m pretty sure you’re just a grocery getter because I’ve yet to see you state any of your own personal real world experience.

 

[silver billet]

And this is why I didn't want to begin the argument. Everything that can be said, has been said, and if you don't get it now well I'm sorry but it appears you won't get it later on either, unless there is some other guy that can that explain better than me.

Bye now.

 

[Rebelguy2020]

Again, common mistake. You're assuming both trucks are in the same numerical gear at the same speed. They won't be. They will be in the same "gear ratio", not the same numerical gear.

The 3.21 will be in 6th (with a gear ratio of 3.21), and the 3.92 will be in 7th (with a gear ratio of 3.2144). Note how though they're in different gears, they actually have an approximately equal gear ratio; meaning, they will have the same rpm at the same speed.

Why the hell are you arguing! You admit the 3.92 will reach the 8th gear sooner, therefore less effort, on both he transmission and the differential.

I am a machinist tool and die technologist for over 4 decades involved in design and fabrication from simple sprockets for chains, straight gears in speed reducers, bevel gear for angle drives, worm gear hoists and complex crown and pinion driven gearboxes, real world experience, so don’t try to sell me “common mistake” end of discussion!

 

[Pristine1]

And this is why I didn't want to begin the argument. Everything that can be said, has been said, and if you don't get it now well I'm sorry but it appears you won't get it later on either, unless there is some other guy that can that explain better than me.

Bye now.

As I’ve told you like a broken record I do actually get what you are putting down. It just goes over your head because You’re beating it like it owes you money. There’s many things you’ve disregarded or left un answered because you are only worried about your point rather than constructive conversation. Sorry if I may have pushed you a little but I was trying to get you to open up to the idea that there’s not a one size fits all. 3.21’s are there for overall fuel efficiency for the average user not for max towing and larger tires.

 

[LoNeStAr]

This is so hilarious

 

[nc_beagle]

As someone deciding between 3.21 and 3.92, this back and forth makes my head spin. I'm probably mid-level when it comes to car knowledge. It seems like the transmission shifts based on RPMs and not MPH, and therefore it's taking advantage of the ratio in a particular gear? Transmissions are smart enough to choose the right ratio for the situation, correct? Whether that means my hypothetical 3.21 is in 5th or my 3.92 is in 6th?

My main curiosity is why the 3.92 has a higher overall tow rating. Is it because the 3.21 would be strained to get off the line with 9K+ being towed?

I do agree with those who wish there was a 3:55 option. I have zero interest in larger tires, but will be towing a 6000# TT with some frequency. The truck won't be a daily driver, but will be used for work (hauling stuff) and long trips (with and without the TT) so I'd really like to find an in-depth look at the MPG difference.

 

[silver billet]

All I can say is, regardless of which gear you choose... check the door jamb sticker of whatever you purchase and make sure it has a high payload available. Don't trust the salesman or a website or a brochure, verify the payload sticker in the actual truck.

There are several limits that kick in while towing: what you can pull, and what you can carry. The 3.92 will give you the highest rated "what you can pull", but if you buy a loaded limited with a 3.92 you're still going to be limited by payload. If the 6000 pounds is accurate, and that is trailer + propane + cargo + water etc, expect 6000 * 0.12 = 720 pounds on the back of your truck just by connecting the trailer. If that 6000 pounds is "dry", then you need to add all that extra stuff to the trailer and reweigh it and now maybe you're at 7000 pounds or whatever. A loaded limited can have <= 1300 pounds of payload in total, so that means by the time you (and say your wife?) hop in, that takes another 400 pounds off the payload, leaving you 180 pounds for luggage in the truck, or kids or a dog etc. You can see how this adds up fast. 3.92 won't save you from Ram's average payload.

You can still get a great truck if you're careful; I have a Big Horn with 1750 pounds of payload because I was careful what I ordered from the factory, because I bought it to tow. No sun roof, no off road group, no air suspension, no ram boxes etc. But it still has the "level 2" tech group which is awesome.

There is no real consensus on how much MPG you save with the 3.21 on the highway, my feeling is at least 3 mpg, others will say "only 1" etc. The highest numbers I've seen have all been 3.21's by a fair margin, you basically run on the highway around 400 rpms lower than the 3.92 would when both are in 8th.

 

[Sascwatch]

I could be wrong, and don't have torque curve numbers or shift pattern data but going by the max torque numbers that the new ecodiesel produces the 3.92 will provide more wheel torque in every gear (22%more) which will allow it to accelerate and hold gears better than the 3.21 under heavy loads which should be more efficient. Max torque for the new ecodiesel is 480ft/lbs. Once you are at cruising speeds the ratios don't matter nearly as much.

3.21
1st gear 480x5.000x3.21=7704
2nd gear 480x3.200x3.21=4930
3rd gear 480x2.1429x3.21=3301
4th gear 480x1.7200x3.21=2650
5th gear 480x1.1319x3.21=1744
6th gear 480x1x3.21=1540
7th gear 480x.8221x3.21=1266
8th gear 480x.64x3.21=986

3.92
1st gear 480x5.000x3.92=9408
2nd gear 480x3.200x3.92=6021
3rd gear 480x2.1429x3.92=4032
4th gear 480x1.7200x3.92=3236
5th gear 480x1.1319x3.92=2129
6th gear 480x1x3.92=1881
7th gear 480x.8221x3.92=1546
8th gear 480x.64x3.92=1204


I know its not a direct comparison but my old truck with a gas motor, 6 speed and 3.08 gears really struggled to tow my enclosed trailer. This new truck accelerates, holds gears better and uses way less fuel than my old truck. I don't think either ratio would be bad with the ecodiesel as it has a much lower peak torque than a gas motor.

I also found this publication by Ram about gear ratios and towing. Its out dated but is still relevent. https://www.ramtruck.ca/en_dir/pdf/RAMFact_2_EN.pdf

This is for the gas motor, but the two ratios are very close in all matches.

Pickup Truck of the Year Winner: 2019 Ram 1500

Owing to its stellar interior, excellent road manners, powerful engine choices, and formidable off-road prowess, the Ram 1500 Rebel is our 2019 Pickup Truck of the Year

www.trucktrend.com

 

[jdefoe0424]

As someone deciding between 3.21 and 3.92, this back and forth makes my head spin. I'm probably mid-level when it comes to car knowledge. It seems like the transmission shifts based on RPMs and not MPH, and therefore it's taking advantage of the ratio in a particular gear? Transmissions are smart enough to choose the right ratio for the situation, correct? Whether that means my hypothetical 3.21 is in 5th or my 3.92 is in 6th?

My main curiosity is why the 3.92 has a higher overall tow rating. Is it because the 3.21 would be strained to get off the line with 9K+ being towed?

I do agree with those who wish there was a 3:55 option. I have zero interest in larger tires, but will be towing a 6000# TT with some frequency. The truck won't be a daily driver, but will be used for work (hauling stuff) and long trips (with and without the TT) so I'd really like to find an in-depth look at the MPG difference.

The tow ratings are based on an sae standard, so I believe the difference between ratios is based on the results from the davis dam portion of the sae standard testing.

Sent from my Moto Z (2) using Tapatalk

 

[Finn5033]

As someone deciding between 3.21 and 3.92, this back and forth makes my head spin. I'm probably mid-level when it comes to car knowledge. It seems like the transmission shifts based on RPMs and not MPH, and therefore it's taking advantage of the ratio in a particular gear? Transmissions are smart enough to choose the right ratio for the situation, correct? Whether that means my hypothetical 3.21 is in 5th or my 3.92 is in 6th?

My main curiosity is why the 3.92 has a higher overall tow rating. Is it because the 3.21 would be strained to get off the line with 9K+ being towed?

I do agree with those who wish there was a 3:55 option. I have zero interest in larger tires, but will be towing a 6000# TT with some frequency. The truck won't be a daily driver, but will be used for work (hauling stuff) and long trips (with and without the TT) so I'd really like to find an in-depth look at the MPG difference.

3.92 for you, don’t over think this. If you’re towing a 6k traveler trailer frequently it’s a no brainer