HO 3.73 vs 4.1?

[gimmie11s]

Why? I am still unclear how a 4.10 ratio will help you at all once you are above first gear. A 4.10 ratio in 6th gear will be very similar to a 3.73 ratio in 5th gear, roughly, I think. Just drop a gear with the 3.73 and all is good. It will be slower to get moving off the line, but after that it just won't matter much. If anyone has evidence (not anecdotes) to the contrary, I would greatly appreciate it being passed along.

The only evidence anyone has is, well, math. Pretty strong anecdote.

 

[gimmie11s]

It's about torque multiplication. But your engine torque is multiplied by both your transmission and your rear axle, if both trucks are at the same mph using a final gear ratio of (say) 3.5, then it doesn't matter how they got there (transmission gear vs rear axle), your rpms will be equivalent, so will your torque multiplication.

Rear axle ratio is badly misunderstood around here and other forums.

But a 3.73 truck and a 4.10 truck will not have the same final drive as each other at the same MPH, ever. That's the point and why the deeper gear is preferred in the towing situation.

Cruising around town unloaded? Who cares, doest really matter.

 

[darrellr]

The only evidence anyone has is, well, math. Pretty strong anecdote.

So, where is the math that shows how much better a 4.10 will perform towing a 21k trailer vs a 3.73 will perform towing the same trailer at highway speeds? Say I am running 65mph down the highway, when and why would I need a 4.10 vs a 3.73? I find very little need for anything more than the HO/AISIN/3.73 setup I have, but I obviously don't know what I am missing I guess. Without the math, as you say, it is only a "strong" anecdote.

 

[darrellr]

RPM has little to do with why 4.10s are better at moving weight its not about how fast your rear end is spinning its about how easy it is to move yes with a taller gear you get more RPM but it also makes things easier to move. People think RPM matters but its only part of the occasion

But how much does the taller gearing matter at highway speeds? I don't generally tow my trailer in stop and go traffic if I can avoid it. So I don't really need to measure any level of performance based on starting from a dead stop too often. I can say my truck doesn't seem to care too much about the 21k trailer with the HO/AISIN/3.73 combo from a dead stop, passing as needed, or pulling grade. But I am not trying to tow 35k, just 21k. I don't even feel the need to lock out 6th gear on a regular basis. For most of us, I just don't see 4.10 really helping that much. Maybe I will find someone who has one like mine but 4.10 gears and I can see for myself.

 

[gimmie11s]

So, where is the math that shows how much better a 4.10 will perform towing a 21k trailer vs a 3.73 will perform towing the same trailer at highway speeds? Say I am running 65mph down the highway, when and why would I need a 4.10 vs a 3.73? I find very little need for anything more than the HO/AISIN/3.73 setup I have, but I obviously don't know what I am missing I guess. Without the math, as you say, it is only a "strong" anecdote.

Read a few posts up where the guy pulling 20k had a hard time passing on the highway. This is exactly what we're talking about.

Or how he could only get 4-5 more mph up the grades towing with his new 3.73 HO truck vs. the SO truck he had prior.

Anecdotes though.. so invalid I guess.


I could go all day telling you about how my 4.10 HO truck performs vs my 2016 SO with 3.42s but again... you seem to not be interested in real-world, user-verified experience.

 

[silver billet]

But a 3.73 truck and a 4.10 truck will not have the same final drive as each other at the same MPH, ever.

The same, no, close enough? Yes. Depending on the exact mph, one truck will have more torque than the other. If the 3.73 is spinning at higher rpms than the 4.10 at the same mph, it's putting more torque to the wheels.

Torque is dependent on both transmission and rear axle. You can "downshift" the rear by changing from the 3.73 to the 4.10, or you can downshift using your transmission gear and get the same effect.

Remember that both trucks are not using the same transmission gear at the same anymore, except for when they're both in first. After that, they'll be using different gears and the final gear ratios can be close enough, or favour the 3.73 depending on the exact mph.

 

[H3LZSN1P3R]

But how much does the taller gearing matter at highway speeds? I don't generally tow my trailer in stop and go traffic if I can avoid it. So I don't really need to measure any level of performance based on starting from a dead stop too often. I can say my truck doesn't seem to care too much about the 21k trailer with the HO/AISIN/3.73 combo from a dead stop, passing as needed, or pulling grade. But I am not trying to tow 35k, just 21k. I don't even feel the need to lock out 6th gear on a regular basis. For most of us, I just don't see 4.10 really helping that much. Maybe I will find someone who has one like mine but 4.10 gears and I can see for myself.

You really don't understand…. The taller gears don't just help at low speed… its called mechanical advantage it helps from the lowest transmissions gear to the highest transmission gear

 

[elephantrider]

leverage baby!!

 

[darrellr]

You really don't understand…. The taller gears don't just help at low speed… its called mechanical advantage it helps from the lowest transmissions gear to the highest transmission gear

I understand quite well actually. But what I want to see, even if anecdotal, is someone who has an HO, AISIN, 3.73 gears and also an HO, AISIN, 4.10 gears in the same features and year and then explain what you are missing with 3.73 gears over the 4.10 gears. Just change that 1 variable. I see gimmie11s compared two vastly different vehicles and said see - it is better, as though that really proved anything. You see these same arguments about fuel octane where people's butt-dynos say higher octane is better but then when you test it - lower octane performs better in the same engine. But if you feel you cannot end up at a VERY similar final drive ratio by adjusting the transmission gear down to change the drive ratio to the same you might see at a 4.10, then you don't understand how the gearing works together. In some very extreme cases, you will see a difference, I give that. But whether you will actually see that on any regular real basis, I question that one. And when you do, it will probably not be on a paved highway / public road - they are too limited on the design parameters to allow highway speed at those grades. And if not at highway speeds, you are back down to low speed take-offs, which again - I gave that one.

 

[silver billet]

Math baby

You head to the store looking for a dozen eggs, there are two options:
Option A) 4 packages of 3 eggs each
Option B) 3 packages of 4 eggs each

Which option is giving you more eggs?

Same thing with torque multiplication.

If truck one is in a transmission gear with a ratio of 4, and the rear axle has a ratio of 3, the final gear ratio is 12.
If truck two is in a transmission gear with a ratio of 3, and the rear axle has a ratio of 4, the final gear ratio is 12 too.

In that scenario, if both trucks are at the same MPH then their RPMs will also be equivalent and they'll be multiplying the torque to the wheels by 100% identical amounts even though the one truck has a much higher rear axle.

You can never look at the rear axle in isolation, you also need to know what transmission gear you are using; that combination of transmission gear and rear axle gear cannot be separated, you need both to come up with your final gear ratio and that's what matters; doesn't matter how you got there, 12 = 12 whether you're using 2X6 or 4x3.

 

[Jimmy07]

I understand quite well actually. But what I want to see, even if anecdotal, is someone who has an HO, AISIN, 3.73 gears and also an HO, AISIN, 4.10 gears in the same features and year and then explain what you are missing with 3.73 gears over the 4.10 gears. Just change that 1 variable.

Not an aisin HO, but I have a 6.4 hemi that I mistakenly ordered with 3:73’s, and I ultimately swapped in the 4:10’s. It is definitely a night and day difference pulling our 9500# camper up same grades we always do, and maintaining a certain speed. The 3:73’s would send the trans a few gears down and let the engine scream out of it’s power band to maintain speed, while the 4:10’s can maintain that same speed without as much effort out of the engine.
So no, taking off in 1st gear is most definitely not the only advantage of different rear gears in my actual real world experience with all else being the same, I don’t care how many different ways someone figures out the math and argues it on paper.

 

[silver billet]

So no, taking off in 1st gear is most definitely not the only advantage of different rear gears in my actual real world experience with all else being the same, I don’t care how many different ways someone figures out the math and argues it on paper.

Confirmation bias my friend, look it up. I can give you anecdotal links from other guys who say they don't notice a single difference.

It's possible that there are specific loads at specific speeds going up specific hills where the one truck has an advantage over the other. But when you change the load, speed, or hill, the other truck can now have an advantage, it's a wash as you'll never find a truck that works the best in every scenario.

Understanding the math/physics is how we know which anecdotes are accurate and which aren't, math never lies.

 

[silver billet]

Final comment on this, another way to look at this, all the rear axle ratio does is shift your 8 gears left/right slightly.

Being a 1500 guy I'm most familiar with my truck, so start with the 3.21 and the ZF 8 speed.

Gears = 1, 2, 3, 4, 5, 6, 7, 8

The 3.92 basically means you open your transmission, shift your gears right, the 8th falls out and you put a deep first gear in the empty spot to the left, you now have:

Gears = 0, 1, 2, 3, 4, 5, 6, 7

You still have 8 gears, you gained a really deep first gear but lost an overdrive.

Both trucks still have gears 1 - 7, they're just in different positions, if either truck is in the gear labeled "6" then their torque multiplication is the same.

For the 2500's and the 3.73 vs 4.10, it's not a complete shift left/right, more like a half step:

Gears = 1, 2, 3, 4, 5, 6, 7, 8 for the 3.73
Gears = 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5 for the 4.10

In some situations, the optimum gear (lowest gear possible to meet the required torque output) might be 6, in others the 5.5 might work better.

This is a little flawed in that the math doesn't actually work that beautifully/cleanly everytime (it does work really well in the 1500 case), sometimes you might get like a 2.647 instead of a 2.5, but the concept itself, that's basically what's happening.

 

[H3LZSN1P3R]

You see these same arguments about fuel octane where people's butt-dynos say higher octane is better but then when you test it - lower octane performs better in the same engine.

Octane is the fuels anti knock quality thats it, now that being said the lower ethanol level of 89+ fuels allow it to preform better. To say lower octane is better is simply a lie

 

[darrellr]

Octane is the fuels anti knock quality thats it, now that being said the lower ethanol level of 89+ fuels allow it to preform better. To say lower octane is better is simply a lie

I didn't say it is better. I did say that you may get better performance out of lower octane fuel than higher octane fuel in engines that do not have high enough compression to take advantage.

 

[darrellr]

Now it all makes sense. You are a flat earther.

Lower octane "performs" better???

View attachment 74258

Name calling - nice.

 

[darrellr]

Not an aisin HO, but I have a 6.4 hemi that I mistakenly ordered with 3:73’s, and I ultimately swapped in the 4:10’s. It is definitely a night and day difference pulling our 9500# camper up same grades we always do, and maintaining a certain speed. The 3:73’s would send the trans a few gears down and let the engine scream out of it’s power band to maintain speed, while the 4:10’s can maintain that same speed without as much effort out of the engine.
So no, taking off in 1st gear is most definitely not the only advantage of different rear gears in my actual real world experience with all else being the same, I don’t care how many different ways someone figures out the math and argues it on paper.

Until someone drives both, it just isn't a valid comparison. In your case, not an aisin, not even a diesel, totally different power and torque curves, apples and oranges.

 

[darrellr]

Why have neither of you been able to provide any output curves? You just sling insults with nothing to back them up. If it is so measurable then prove it.

 

[H3LZSN1P3R]

Why have neither of you been able to provide any output curves? You just sling insults with nothing to back them up. If it is so measurable then prove it.

You have not provided any either? Besides the output of 4.10 gears over 3.73 would be straight not curved on a graph….

But here is an example of the increased mechanical advantage going with taller gears for jeeps the same applies for any vehicle just engine power and trans range changes the RPM number

 

[darrellr]

Yay, another sample of apples and oranges. Jeeps are not towing 20k+ trailers and the use case is not the same. Jeeps often have larger tires that will absolutely make use of the taller gears else they may be limited to about 50mph on the highway. Yeah, I own Jeeps, too. I am the first one that asked for it - yet no one has provided it.

The curves will come from a chassis dyno off wheel outputs resulting from the engine output through the entire drive line, not just the rear end. Within the usable speed bands when towing, what will the delta be between 4.10 and 3.73 at highway speeds pulling 20k up an 8% incline and what will the difference be when you are just 1 gear lower with the 3.73 vs the 4.10? Power difference? Doubtful. Fuel efficiency, likely a wash in this use case. All other use cases, better mileage and driving experience with the 3.73 unless you are always hauling around 39k or you have decided to increase the tire size from design and need to compensate.

Again, I know what taller gears can get you, but my argument is that they are not nearly as required as a lot of people on this forum seem to espouse they are. An aisin with 3.73 gears will work for anyone just hauling an RV and most folks hauling farm equipment for alfalfa. Just about anything else is just people getting into pissing contests.

Your signature doesn't indicate that you even drive either of these models I am asking about....why should anyone listen to your real-world experience based on the subject line of this thread???

Edited to add tire size as another reason to increase rear end ratio.