An Engineer's Ultimate Guide To 3.21 VS 3.92 Axle Ratio

[BowDown]

Yep.

Interesting. When I manually lock out 8th, my rpms jump from 1700ish to 21-2200ish, tried it yesterday. Either way, my truck is exactly as I wanted it as I'm sure yours is so its all good

 

[Idahoktm]

Interesting. When I manually lock out 8th, my rpms jump from 1700ish to 21-2200ish, tried it yesterday. Either way, my truck is exactly as I wanted it as I'm sure yours is so its all good

I have 33" tires and I know that makes a small difference, but I'm not sure how much. I suppose I could do the math but....

 

[HSKR R/T]

I'll have to take a pic of mine next time I'm on the freeway, for proof, but I know it's 1900 rpm's.

You have taller tires on your truck, which will lower your final drive RPM.

 

[Usmc041127]

I wonder if there is a difference in the hp and torque in the different rpms. Maybe the one gear or the other is in a higher power level at 70 mph just because of the power band in the engine. One would have to look at the hp and torque curves to see what is the optimal gear and speed is for the engine to be putting out maximum hp or torque.

 

[SnowBlaZR2]

Since you know what a frikin mango frappe is, tells me a lot. I don’t think I would like it, too much sugar.

I know what 3.21s and women are, too. All three were made for each other.

 

[Ramroo]

I know what 3.21s and women are, too. All three were made for each other.

I do love my 3.21 truck, and I do love women. I know that I won’t like your fruity drink
though, because I don’t like the sweet drinks. Im trying to make some sense from your comment and came to the conclusion that you are one of those guys that try to make fun of other people if they are different or have something different than you. I can see through you like you are glass.

 

[Idahoktm]

You have taller tires on your truck, which will lower your final drive RPM.

Yep, that's pretty much what I said.

 

[Mountain Whiskey]

Born and raised on 4 year old Jim Beam.
Since you drink whiskey with coke says it all!!!!

Yea, bottom shelf taxed liquor and proud? 3.21 for sure.

 

[SnowBlaZR2]

I do love my 3.21 truck, and I do love women. I know that I won’t like your fruity drink
though, because I don’t like the sweet drinks. Im trying to make some sense from your comment and came to the conclusion that you are one of those guys that try to make fun of other people if they are different or have something different than you. I can see through you like you are glass.

I think dudes who are genuinely insecure about their trucks are somewhat amusing. Dudes who are insecure about their garbage whiskey are even more amusing.

But hey, you have it all figured out. Keep it going.

 

[cleandirt]

Yea, bottom shelf taxed liquor and proud? 3.21 for sure.

You might as well be drinking bottom shelf liquor too if your mixing it with coke, sheesh


Sent from my iPad using Tapatalk

 

[Ramroo]

Yea, bottom shelf taxed liquor and proud? 3.21 for sure.

OK, Ok.
I‘ve got a funny story to tell you. So last night I was telling my wife and daughter about you. I gave them a little quick background on you first... So this guy gave himself a cool nickname called Mountain Whiskey, drives a lifted while leveled full size truck with big tires and no airbags that he thinks looks cool but it can’t safely haul or tow any kind of weight, and loves to make fun of people with different trucks while driving that castrated truck. Then he ( remember he gave himself the nickname Mountain Whiskey ) said he drinks his whiskey with COKE! My wife and daughter laughed their *** off.
So, I’m making this forum more like the military where cool sounding nicknames and call signs are earned. Since your nickname was self given, I am pulling your nickname and giving you your new nickname called Fake. You might get another nickname but you have to quit saying stupid stuff about other people because of their trucks or opinions while having driving a truck like yours.
Also, if you get a new nickname, it WILL NOT have anything to do with whiskey. You have embarrassed yourself and showed you have been bluffing the whole time. I have had the pleasure of working with, and associating with people that work and play hard, and love drinking bourbon and whiskey. I can’t honestly think of one person, male or female that drinks OR openly admits to drinking whiskey with COKE... NOT in my circle, don’t happen.

 

[Ramroo]

I think dudes who are genuinely insecure about their trucks are somewhat amusing. Dudes who are insecure about their garbage whiskey are even more amusing.

But hey, you have it all figured out. Keep it going.

I totally agree with with your first comment.
I don’t follow your second comment. Im sure your commenting my 4 year old Jim Beam comment. I am definitely NOT insecure about the whiskey I drink (or truck I drive). I have not always had the money that I could spend on expensive whiskey, so I drink what I personally think is good bourbon that is not expensive. The ironic thing I have found, is that the people make fun of cheap bourbon are the whiskey snobs that love to spend money on expensive whiskey because it makes them feel better about their inadequacies or insecurities, maybe that’s you. I have drank some expensive whiskey that was good, just does not justify the price in my opinion.

 

[Mountain Whiskey]

OK, Ok.
I‘ve got a funny story to tell you. So last night I was telling my wife and daughter about you. I gave them a little quick background on you first... So this guy gave himself a cool nickname called Mountain Whiskey, drives a lifted while leveled full size truck with big tires and no airbags that he thinks looks cool but it can’t safely haul or tow any kind of weight, and loves to make fun of people with different trucks while driving that castrated truck. Then he ( remember he gave himself the nickname Mountain Whiskey ) said he drinks his whiskey with COKE! My wife and daughter laughed their *** off.
So, I’m making this forum more like the military where cool sounding nicknames and call signs are earned. Since your nickname was self given, I am pulling your nickname and giving you your new nickname called Fake. You might get another nickname but you have to quit saying stupid stuff about other people because of their trucks or opinions while having driving a truck like yours.
Also, if you get a new nickname, it WILL NOT have anything to do with whiskey. You have embarrassed yourself and showed you have been bluffing the whole time. I have had the pleasure of working with, and associating with people that work and play hard, and love drinking bourbon and whiskey. I can’t honestly think of one person, male or female that drinks OR openly admits to drinking whiskey with COKE... NOT in my circle, don’t happen.

See, obvious 3.21 guy.

Telling stories to little girls to sound important. Men see through the BS. Just don't pretend that bottle of rot gut Beam you have been nursing for 4 years makes you a "hard playin' man". Sipping it while having a tea party with stuffed animals does not count as drinking.

Men drink whatever they like however they like it. Certainly not bottom shelf tax liquor. Have your teaparty. The little girls and stuffed animals will likely believe that you are a "hard workin' hard playin' man". They will also believe it when you tell then the fairytales of how mighty your truck is with 3.21 gears.

 

[Ramroo]

See, obvious 3.21 guy.

Telling stories to little girls to sound important. Men see through the BS. Just don't pretend that bottle of rot gut Beam you have been nursing for 4 years makes you a "hard playin' man". Sipping it while having a tea party with stuffed animals does not count as drinking.

Men drink whatever they like however they like it. Certainly not bottom shelf tax liquor. Have your teaparty. The little girls and stuffed animals will likely believe that you are a "hard workin' hard playin' man". They will also believe it when you tell then the fairytales of how mighty your truck is with 3.21 gears. View attachment 124366

Can’t help but smile while reading your comments. You do have a sense of humor.
The funniest thing you said is that “Men see through the BS”. Yes, yes they do.

 

[Ramjack]

Pic while cruising with stock laramie tires. Both trucks stock.

Yep, that makes perfect sense if you're running 1750-ish with 3.21 gears.

 

[Ramjack]

I wonder if there is a difference in the hp and torque in the different rpms. Maybe the one gear or the other is in a higher power level at 70 mph just because of the power band in the engine. One would have to look at the hp and torque curves to see what is the optimal gear and speed is for the engine to be putting out maximum hp or torque.

Interesting question. Can you clarify what you're getting at? Neither truck is going to generate more hp at 70mph regardless of rpm. They will be generating the exact same power assuming they are holding a steady 70mph and not accelerating. But the truck running higher rpm's will have the throttle less open. I imagine what you're thinking about is that the engine may have the ability to generate more power at a higher rpm (i.e. at WOT) but it isn't actually doing so because the throttle is not wide open (or at least, not more open).

 

[Usmc041127]

Interesting question. Can you clarify what you're getting at? Neither truck is going to generate more hp at 70mph regardless of rpm. They will be generating the exact same power assuming they are holding a steady 70mph and not accelerating. But the truck running higher rpm's will have the throttle less open. I imagine what you're thinking about is that the engine may have the ability to generate more power at a higher rpm (i.e. at WOT) but it isn't actually doing so because the throttle is not wide open (or at least, not more open).

Engine's have a power band and torque band. The easiest way to explain it is like your old 2 stroke dirtbike Engine's. They have a specific RPM power band. Any more and any less RPM and they didn't have much power. A camshaft has a specific profile to have an RPM range that it at its strongest. Stock ones are generally idle to 5500 rpms and power falls off after 5500 rpms. RV or popular towing cam will bring the power band up to say 1500 RPM to 6000 RPM. I'm curious what the power band and torque curve is on the 5.7 hemi engines. Im sure there is a sweet spot in the cam profile that puts the engine in and ideal RPM for maximum hp and torque. So the closer it is to your ideal cruising speed it would be better. If your engine has peak hp and torque at say 1800 to 2000 RPMs idealy you would want your cruising speed to be in that range. It would reduce downshifting. Thats where the rear end gears could play a role. It puts the engine at certain RPM at cruising speed.

 

[SnowBlaZR2]

I totally agree with with your first comment.
I don’t follow your second comment. Im sure your commenting my 4 year old Jim Beam comment. I am definitely NOT insecure about the whiskey I drink (or truck I drive). I have not always had the money that I could spend on expensive whiskey, so I drink what I personally think is good bourbon that is not expensive. The ironic thing I have found, is that the people make fun of cheap bourbon are the whiskey snobs that love to spend money on expensive whiskey because it makes them feel better about their inadequacies or insecurities, maybe that’s you. I have drank some expensive whiskey that was good, just does not justify the price in my opinion.

You're putting a lot of time in trying to convince us that you're OK with your choices. Seems a little insecure to me.

And I drink black label Jack unless it's something my wife gets me as a gift, but I wouldn't throw that out as "proof" that I don't drink mango frappes. You actually wanted the 3.21s. No amount of garbage whiskey will overcome that.

 

[Ramjack]

Im sure there is a sweet spot in the cam profile that puts the engine in and ideal RPM for maximum hp and torque. So the closer it is to your ideal cruising speed it would be better. If your engine has peak hp and torque at say 1800 to 2000 RPMs idealy you would want your cruising speed to be in that range. It would reduce downshifting. Thats where the rear end gears could play a role. It puts the engine at certain RPM at cruising speed.

If you are trying to maximize MPG, the short (and theoretical) answer is simple: The vehicle requires a certain amount of horsepower to overcome friction and air resistance to maintain a certain speed, regardless of gearset or engine speed. So let's say you are trying to maintain 70mph on a flat road. I have no idea how much horsepower that requires for the Ram 1500 but let's say it's 25hp. The engine can generate 25 hp at a wide variety of rpm levels depending on the throttle opening, right? It can generate 25hp at 1750rpm or it can generate 25 hp at 2200 rpm (and everywhere in between). The general rule of thumb is that the more the engine is generating the desired hp through torque as opposed to rpm, the better the fuel economy. So an engine you are asking to generate 25hp at 1750rpm (Scenario A) is generating a higher level of torque than the same engine you are asking to generate 25hp at 2200rpm (Scenario B). Scenario A will result in better fuel-efficiency, mostly because of lower throttling losses.

CAVEAT: Keep in mind that the debate it this 90-page thread isn't about which gearset yields better fuel efficiency at a steady-state 70mph on a flat highway. It's more about can the 3.92 gearset do as well or better than the 3.21 under certain circumstances. Unfortunately, there are two many variables (8 speed transmission, timing of MDS activation, the propensity of 3.92 truck owners to be morbidly overweight, etc. - no, not really) to answer the question definitively for all circumstances.

 

[Mountain Whiskey]

If you are trying to maximize MPG, the short (and theoretical) answer is simple: The vehicle requires a certain amount of horsepower to overcome friction and air resistance to maintain a certain speed, regardless of gearset or engine speed. So let's say you are trying to maintain 70mph on a flat road. I have no idea how much horsepower that requires for the Ram 1500 but let's say it's 25hp. The engine can generate 25 hp at a wide variety of rpm levels depending on the throttle opening, right? It can generate 25hp at 1750rpm or it can generate 25 hp at 2200 rpm (and everywhere in between). The general rule of thumb is that the more the engine is generating the desired hp through torque as opposed to rpm, the better the fuel economy. So an engine you are asking to generate 25hp at 1750rpm (Scenario A) is generating a higher level of torque than the same engine you are asking to generate 25hp at 2200rpm (Scenario B). Scenario A will result in better fuel-efficiency, mostly because of lower throttling losses.

CAVEAT: Keep in mind that the debate it this 90-page thread isn't about which gearset yields better fuel efficiency at a steady-state 70mph on a flat highway. It's more about can the 3.92 gearset do as well or better than the 3.21 under certain circumstances. Unfortunately, there are two many variables (8 speed transmission, timing of MDS activation, the propensity of 3.92 truck owners to be morbidly overweight, etc. - no, not really) to answer the question definitively for all circumstances.

So, what you are saying is:
3.21= Girlie Grocery Getter
3.92= Truck.