3.55 vs 3.73 - Mustang Evolution

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Old 11-04-2012, 09:24 AM   #1
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3.55 vs 3.73

I'm about to buy gears for my 8.8, the guy has both ratios, I wanna hear your guys opinions on both. Mine is a daily, but I want that throw you in your seat kinda torque. I have 18 inch rims so I don't think traction will really be an issue either
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Old 11-04-2012, 09:30 AM   #2
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If you do quite a bit of highway id say 3.55. If your all city driving then 73.
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Old 11-04-2012, 09:32 AM   #3
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Originally Posted by Surffer227
I'm about to buy gears for my 8.8, the guy has both ratios, I wanna hear your guys opinions on both. Mine is a daily, but I want that throw you in your seat kinda torque. I have 18 inch rims so I don't think traction will really be an issue either
Definitely 3.73 if you want any kind of throw you back in ur seat feel
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Old 11-04-2012, 11:31 AM   #4
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3.73 no questions there
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Old 11-04-2012, 11:35 AM   #5
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3.73
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Old 11-04-2012, 11:45 AM   #6
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Quote:
Originally Posted by Surffer227
I'm about to buy gears for my 8.8, the guy has both ratios, I wanna hear your guys opinions on both. Mine is a daily, but I want that throw you in your seat kinda torque. I have 18 inch rims so I don't think traction will really be an issue either
How much did you pay for the 8.8 rear end? I wanna do that swap soon but I can't find a good price on any
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Old 11-04-2012, 12:50 PM   #7
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I have 4.10s and LOVE em! i dont think 3.73 will throw u back to much... but then again i have never driven with 3.73s
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Old 11-04-2012, 04:37 PM   #8
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I have 4.10s and LOVE em! i dont think 3.73 will throw u back to much... but then again i have never driven with 3.73s
Do you have an auto or manual?
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Old 11-05-2012, 05:54 PM   #9
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Manual. I have the FRPP Cams so because they are for higher RPM i needed to make up the Lower RPM so went with the 4.10s. I can actually spin tires at 100mph! YES you read that right 100mph! I have a youtube video proving it at Epping Dragway in NH. just check out my channel. Search MDoane44 on Youtube. but go with 4.10s!!!!!!!!! return what you have and just do it! you can thank me later...lol
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Old 11-06-2012, 01:34 AM   #10
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Weren't you wanting to do a turbo build or something? If that's still the case just get 3.55's
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Old 11-06-2012, 06:46 AM   #11
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Weren't you wanting to do a turbo build or something? If that's still the case just get 3.55's
Are 3.73sto tall for turbo?
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Old 11-06-2012, 07:21 AM   #12
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Originally Posted by Surffer227

Are 3.73sto tall for turbo?
Not really, just common place for 3.27-3.55's
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Old 11-06-2012, 08:33 AM   #13
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Depends on how much power you go with turbo. You want to stay in the power band as long as possible that's why lower gears are better for forced induction
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Old 11-06-2012, 08:35 AM   #14
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Well wouldn't you get into boost quicker with taller gears
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Old 11-06-2012, 06:26 PM   #15
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Yes you will hit the power band faster but you will also leave it faster because once the boost kicks in its going to push you through the rpms
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Old 11-12-2012, 02:27 PM   #16
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Originally Posted by Surffer227 View Post
I'm about to buy gears for my 8.8, the guy has both ratios, I wanna hear your guys opinions on both. Mine is a daily, but I want that throw you in your seat kinda torque. I have 18 inch rims so I don't think traction will really be an issue either
3.73 is satisfying, but you will want more. 3.55 is almost no change in performance at all, so what's the point? I kindof wish I had done 3.90, but 4.10 seems like it would be too steep for a dd. If I were you, I would go with 3.73, or 3.90. As for gas mileage, it will all depend on how you drive. You actually burn less gas by keeping your RPMs higher, it has been proven. This is because it takes less energy to keep everything moving/turning/rotating than it does to get everything moving. The reason people feel like they have lost gas mileage with steeper gears is that they usually install TLOK with new gears, which DOES reduce gas mileage considerably, and also people usually romp on the gas more once they have the new gears, since they feel like they have a ferrari all of a sudden after simple mods.
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Old 11-12-2012, 02:36 PM   #17
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Well wouldn't you get into boost quicker with taller gears
Yes, and you will top out too fast and end up making loud "oh my God I can't find the gear" noises. In lamen's terms, you will go through the gears way too fast. With 6 cylinder boosted mustangs, 3.73 is by far the most popular, but depending on your other mods (if any), your optimum gearing may be lower. I have read many many horror stories of people boosting their stang and leaving the 3.90s or 4.10s in.
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Old 11-12-2012, 04:46 PM   #18
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3.73 is satisfying, but you will want more. 3.55 is almost no change in performance at all, so what's the point? I kindof wish I had done 3.90, but 4.10 seems like it would be too steep for a dd. If I were you, I would go with 3.73, or 3.90. As for gas mileage, it will all depend on how you drive. You actually burn less gas by keeping your RPMs higher, it has been proven. This is because it takes less energy to keep everything moving/turning/rotating than it does to get everything moving. The reason people feel like they have lost gas mileage with steeper gears is that they usually install TLOK with new gears, which DOES reduce gas mileage considerably, and also people usually romp on the gas more once they have the new gears, since they feel like they have a ferrari all of a sudden after simple mods.
a t-lok decreasing mileage... that is the first time I have ever heard that
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Old 11-12-2012, 05:51 PM   #19
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Tlock reducing mileage.... Say it aint so. Steeper gears are what reduces mileage, you turn 3500rpms at 70mph and let me turn 2800 and see who runs out of gas first lol...


Gears and boost kind of depend on the type of forced induction....

Turbo: stock gears work fine, 3.55s work great
Centri: 3.73s work great, 4.10s work
Positive displacement: stock gears work fine again... or whatever you want
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Old 11-13-2012, 07:12 AM   #20
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a t-lok decreasing mileage... that is the first time I have ever heard that
Probably because everyone blames it on the gears!

Takes more gas to turn two wheels at the same rate than it does 1!

This is why 4wd cars burn the most gas!



---------- Post added at 08:12 AM ---------- Previous post was at 08:11 AM ----------

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Tlock reducing mileage.... Say it aint so. Steeper gears are what reduces mileage, you turn 3500rpms at 70mph and let me turn 2800 and see who runs out of gas first lol...


Gears and boost kind of depend on the type of forced induction....

Turbo: stock gears work fine, 3.55s work great
Centri: 3.73s work great, 4.10s work
Positive displacement: stock gears work fine again... or whatever you want
All else the same, you will. I gotta find that link....

Think about it, when you run, is it easier to do suicides or run a straight mile? You spend more energy stopping and going in your run than if you just kept jogging the entire length of a track. Inertia and motion and laws of physics and all that...
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Old 11-13-2012, 08:16 AM   #21
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I hate to tell you but your wrong about the t lok. When you drive an open diff the power is being put to both wheels. The difference is that when one wheel slips there is nothing to help the power get back to the other side. On a posi vehicle when you drive normally, it drives normally. But when you peel out the the posi locks up to transfer power to the wheel that isn't spinning as fast. NOW for 4wd. That's like driving a rear wheel drive and adding a front wheel drive trans also(aka transfer case) so when in 4wd you are turning twice the transmission you were in 2wd which puts more load on the engine. Gas mileage is most effected by load not entirely rpms
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Old 11-13-2012, 10:58 PM   #22
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Probably because everyone blames it on the gears!

Takes more gas to turn two wheels at the same rate than it does 1!

This is why 4wd cars burn the most gas!

All else the same, you will. I gotta find that link....

Think about it, when you run, is it easier to do suicides or run a straight mile? You spend more energy stopping and going in your run than if you just kept jogging the entire length of a track. Inertia and motion and laws of physics and all that...
really more gas to turn two wheels, sure you might use more gas in a burnout with that understanding... but if you're going forward both are turning whether it's a full spoil or an open differential...

btw i changed my diff first before gears (like two years before) there was 0 change in gas mileage

as to the 4wd part i'm not even going to bother just
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Old 11-13-2012, 11:08 PM   #23
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So let's get this straight. I have an 04 automatic V6 if I get either 3.73 gears or 4.10. Can I just buy a tuner from AM and my spedometer will be fine?
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Old 11-13-2012, 11:11 PM   #24
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So let's get this straight. I have an 04 automatic V6 if I get either 3.73 gears or 4.10. Can I just buy a tuner from AM and my spedometer will be fine?
yes that will work just fine
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Old 11-14-2012, 07:03 AM   #25
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I hate to tell you but your wrong about the t lok. When you drive an open diff the power is being put to both wheels. The difference is that when one wheel slips there is nothing to help the power get back to the other side. On a posi vehicle when you drive normally, it drives normally. But when you peel out the the posi locks up to transfer power to the wheel that isn't spinning as fast. NOW for 4wd. That's like driving a rear wheel drive and adding a front wheel drive trans also(aka transfer case) so when in 4wd you are turning twice the transmission you were in 2wd which puts more load on the engine. Gas mileage is most effected by load not entirely rpms
No sir. An open diff does not put power to both wheels, the second wheel is pulled along with the first. I have never heard anyone say otherwise. The posi is going to lock both wheels the majority of the time, because how often do people do all this work to their mustangs so they can drive them like a granny?

"so when in 4wd you are turning twice the transmission you were in 2wd which puts more load on the engine"

...right....and powering 1 wheel is half the load of 2.

---------- Post added at 08:03 AM ---------- Previous post was at 08:00 AM ----------

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really more gas to turn two wheels, sure you might use more gas in a burnout with that understanding... but if you're going forward both are turning whether it's a full spoil or an open differential...

btw i changed my diff first before gears (like two years before) there was 0 change in gas mileage

as to the 4wd part i'm not even going to bother just
Both are turning, but you aren't powering both wheels.

Were you looking for the change in gas mileage, or are you just trying to recall now?

How is it that by keeping your RPM's higher (meaning less "revving up" required by the engine) you place more load on the engine? Explain this to me. Most of the gas burns while getting up to speed, not while already up to speed. I guess I can see how highway miles might suffer a small amount from higher gears, but more than made up for in street driving.
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Old 11-14-2012, 07:30 AM   #26
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Both are turning, but you aren't powering both wheels.

Were you looking for the change in gas mileage, or are you just trying to recall now?

How is it that by keeping your RPM's higher (meaning less "revving up" required by the engine) you place more load on the engine? Explain this to me. Most of the gas burns while getting up to speed, not while already up to speed. I guess I can see how highway miles might suffer a small amount from higher gears, but more than made up for in street driving.
You're powering both wheels with an open differential it may not be a 50/50 split of power but you are... And here is why I still don't believe you... Either with an open or LSD you only put 100% of power to the tires no matter the distribution it's always the same amount of power... In other words by putting power to both wheels you take away some power that was used for the one wheel to even the distribution
Of course another point to your argument a LSD acts as an open differential until you put a heavy load on it or one tire starts spinning..

For the point you're trying to make you would have to take a true one wheel drive system (meaning power goes to a diff that just goes to one wheel) and make it into a two wheel drive system

As to the gas mileage I have ~90% of my trips from the time I owned the car written down but it's easy to remember that my mileage changed little if at all until the motor work was down
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Old 11-14-2012, 08:21 AM   #27
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The reason why MPG is worse on a car with T-Lok is because of rotational mass. There's simply more moving. The T-Lok clutches activate under many circumstances, not just flooring it. Perfect evidence of that is in the snow. Next time you slip (traction control off) you will see both rear wheels spinning, even under light loads. That said, the MPG will be so small, it will be hard to notice.

Posi traction is a GM thing from back in the day and it's both wheels all the time. Around turns, both tires spin at equal rotation speeds. Limited slip and Ford's Traction-Lok (their version of limited slip) allows the outer wheel to spin faster around turns, which makes for a smoother turn.
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Old 11-14-2012, 11:38 AM   #28
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Manual. I have the FRPP Cams so because they are for higher RPM i needed to make up the Lower RPM so went with the 4.10s. I can actually spin tires at 100mph! YES you read that right 100mph! I have a youtube video proving it at Epping Dragway in NH. just check out my channel. Search MDoane44 on Youtube. but go with 4.10s!!!!!!!!! return what you have and just do it! you can thank me later...lol
4:10s
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Old 11-15-2012, 06:28 AM   #29
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You're powering both wheels with an open differential it may not be a 50/50 split of power but you are... And here is why I still don't believe you... Either with an open or LSD you only put 100% of power to the tires no matter the distribution it's always the same amount of power... In other words by putting power to both wheels you take away some power that was used for the one wheel to even the distribution
Of course another point to your argument a LSD acts as an open differential until you put a heavy load on it or one tire starts spinning..

For the point you're trying to make you would have to take a true one wheel drive system (meaning power goes to a diff that just goes to one wheel) and make it into a two wheel drive system

As to the gas mileage I have ~90% of my trips from the time I owned the car written down but it's easy to remember that my mileage changed little if at all until the motor work was down
Well, I think you need to go study differentials.

An open differential powers one wheel, the other spins with it.

An LSD like TLOK powers both wheels most of the time when you are going in a straight line and both wheels are experiencing about the same amount of friction. This places more load on the motor most of the time, and from a physics standpoint, burns more gas.

A fully locked differential would only be seen in drag, and will burn even more gas if you ride around on the street with one.

It's just science and common sense, but I understand that when everyone has been saying "it's the gears not the tlok that make you burn gas because high RPMS make you burn gas right" - this makes it hard to actually notice otherwise.

Ask someone with 4.10s and they will tell you that at 60 MPH they are at 2.5k RPM, and it really doesn't burn that much more gas on the highway.. In the city you will save gas.

You write down all your trips? Crazy bro.

---------- Post added at 07:28 AM ---------- Previous post was at 07:25 AM ----------

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The reason why MPG is worse on a car with T-Lok is because of rotational mass. There's simply more moving. The T-Lok clutches activate under many circumstances, not just flooring it. Perfect evidence of that is in the snow. Next time you slip (traction control off) you will see both rear wheels spinning, even under light loads. That said, the MPG will be so small, it will be hard to notice.

Posi traction is a GM thing from back in the day and it's both wheels all the time. Around turns, both tires spin at equal rotation speeds. Limited slip and Ford's Traction-Lok (their version of limited slip) allows the outer wheel to spin faster around turns, which makes for a smoother turn.
Thank you, I am glad I am not the only one here who has read up on this.
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Old 11-15-2012, 01:30 PM   #30
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From my own personal experience over ~2 years it made 0 NOTICEABLE difference in mileage for t-lok alone, more than enough evidence for me

As for the gears yes we all know it hurts highway mileage and helps city IF you drive right
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Old 11-15-2012, 01:43 PM   #31
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From my own personal experience over ~2 years it made 0 NOTICEABLE difference in mileage for t-lok alone, more than enough evidence for me
I really don't think you would notice it. I think it would be in the tenths. You'd have to have the same number of miles and the same driving habits between a before T-Lok and after T-Lok MPG comparison. I'm guessing it would be .20 to .40 more. This is JMO.
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Old 11-15-2012, 02:14 PM   #32
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The reason why MPG is worse on a car with T-Lok is because of rotational mass. There's simply more moving. The T-Lok clutches activate under many circumstances, not just flooring it. Perfect evidence of that is in the snow. Next time you slip (traction control off) you will see both rear wheels spinning, even under light loads. That said, the MPG will be so small, it will be hard to notice.

Posi traction is a GM thing from back in the day and it's both wheels all the time. Around turns, both tires spin at equal rotation speeds. Limited slip and Ford's Traction-Lok (their version of limited slip) allows the outer wheel to spin faster around turns, which makes for a smoother turn.

1) A tlock or positive trac differential will NOT effect real world mileage.
2) Posi traction is a GM thing (made by eaton) and it is not a locker, a spool, or anything close to keeping both wheels turning at the same time. It's just GM's name for what ford calls limited slip.
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Old 11-15-2012, 03:37 PM   #33
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After searching, I'll admit I'm wrong about the positraction. First, I didn't think Chevy/GMC still used "Positraction" anymore. Second, I thought Posi was a locker from the 50's to 70's. I thought limited slip replaced it. Again, I was wrong.. Thanks for clearing that up.

Guide to Limited Slip Differentials

It only makes sense that with more rotating mass, an LSD would have a slightly higher MPG. As I stated, it may difficult to measure, because we can't simulate exact driving habits to get true before and after data. Are you saying that there is not more rotating mass or drag between an open diff and an LSD diff?
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Old 11-16-2012, 08:11 AM   #34
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Originally Posted by ChrisTorres08 View Post
1) A tlock or positive trac differential will NOT effect real world mileage.
2) Posi traction is a GM thing (made by eaton) and it is not a locker, a spool, or anything close to keeping both wheels turning at the same time. It's just GM's name for what ford calls limited slip.
My original point was that the gears are even less likely to be the culprit. The loss from extra rotating mass placing extra load on the motor is far quicker to cause loss of mpg than being at 2500 RPM with 4.10's versus 2000 with the 3.27's or in my case with 3.73's @ 2200 (60MPH approximations).

I was just trying to clear up a common misconception.

/end debate.
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Old 11-16-2012, 10:20 AM   #35
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How much is it to get a shop to install gears? Ive heard anywhere from $200 to $900
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