EcoModder.com

EcoModder.com (https://ecomodder.com/forum/)
-   EcoModding Central (https://ecomodder.com/forum/ecomodding-central.html)
-   -   Worth changing gears to imporve Fuel Economy? (https://ecomodder.com/forum/showthread.php/worth-changing-gears-imporve-fuel-economy-3907.html)

2000mustang fan 07-18-2008 02:29 PM

Worth changing gears to imporve Fuel Economy?
 
:confused:

So, my question is, Would changing my Mustang's stock 3.27 rear gears to 2.73 increase my fuel economy and by how much possible? I have the scangauge II now and am getting between 24-25MPG this tank so far with 2Gals used. how much MPG increase would this be? Also could I change the driveshaft to Aluminimum to increase FE or would that just hurt FE because it would be lighter and lose momentum fast while coasting? Also I was told that my rear is 7.5" is it possible to increase that to an 8.5" to acheive better FE or does that defeat the purpose as well? I also have a question, which I don't know if this is the same thing but how can I improve acceleration without using 2GPH at 1365RPM when staring off at a dead stop without hitting the accelrator hard at all. Because that is what is really killing my FE from breaking to consistent 26MPG. With the scangaugeII is it possible to limit the amount of gas the throttle intakes at a certain RPM speed. And I know some engines change gears under load, but my Mustang only changes at Certain RPMs say from 0-15 1st gear, then at 1250RPM(21-22MPH) it will switch to 2nd and be at 1000RPM using slightly less fuel. then once it reaches 30MPH at 1500RPM it will switch to third and drop to 1250RPM. Then at 40MPH at 1550RPM it switches to Fourth gear and I'm not sure if 4th gear s OD or not cause it said it's a 4Speed Auto W/OD but around 47MPH I can get 45MPG and on the highway ScangaugeII reprots 33-35MPG at 55MPH. Is there a way to increase FE somehow knowing this like with a tuner or something?

You don't have to answer them all, Even If you know only one answer to this it will be greatly appreciated Thanks :)

EDIT: I do have a CAI I was looking at threads based on WAI, stock or CAI shouls I keep what I have go back to stock or ge a WAI?????

SVOboy 07-18-2008 02:32 PM

I would say to go for the gear swap. It should be simple on your mustang, right? The other questions are a bit more complicated though...perhaps when I wake up, :)

twentysixtwo 07-18-2008 02:57 PM

I worked on Mustang FE in a former life. The axle ratio swap will definitely give improved mileage, though somewhere on the order of perhaps half a mpg. May or may not be worth the investment but certainly if you can get it for cheap and DIY

Aluminum driveshaft will give better FE from weight and reduced inertia - drilling out a flywheel will have the same effect. I cannot think of any real world situation where an Al driveshaft will hurt.

IIRC the 7.5 and 8.5 refer to the diff gear size, in which case I'd recommend you stick with the smaller (lighter) one. The bigger one can handle more torque if you're doing burnouts and the like which I assume you're not. Besides being lighter, less fluidic losses.

Don't have an answer to your last questions. The "K" factor of your torque converter is at fault here but I don't think you can change that easily.

garys_1k 07-18-2008 06:42 PM

The final drive ratio swap will improve highway FE, absolutely. Maybe a mile per gallon, likely more. Its effect on city driving, below 45 mph, is a LOT iffier. I wouldn't count on any gain there (you'd likely delay upshifts, that's about all) so the average engine speed can remain about the same. But if you do highway driving the most, you'd be seeing a real gain.

Of course, if you could recalibrate the shifts to work at the same vehicle speeds, then you'd be more likely to gain in city driving, too. I'm not sure how it's now calibrated -- to work off real vehicle speed or transmission output shaft (driveshaft) speed. If it's the latter than you'd definitely just delay upshifts with a lower numerical final drive.

Your four speed auto has an overdrive (ratio less than 1:1) in top gear. The somewhat higher FE you're seeing after being in 4th already, at a higher vehicle speed, is from the torque converter clutch locking up. That is DEFINITELY a good thing for FE.

Red 07-18-2008 11:49 PM

New gears could be as easy as just swapping in a new rear end. IIRC 00 Mustangs still used a solid rear axle so it shouldn't be too hard. Will net you gains highway cruising.

Lowering rotational mass always helps.

The aftermarket on Mustangs is huge, there should be some kind of reprogrammer you could get for your ECU To change the shift points.

reformed 07-19-2008 01:11 AM

Swapping to an 8.8" (the GT rearend) will do nothing for FE, You're way better off sticking with your 7.5" and putting in the 2.73's. This may or may not help though depending on where your power curve is. I would suggest talking to other v6 mustang owners about that before you do the swap. I'm a member at moddedmustangs.com and there are some pretty knowledgable people over there in the V6 section who can probably answer that question. If you do go over there to the V6 section, be patient with your question though, there are a lot of younger kids who like to hear themselves talk in there so you have to sift through their answers.

Red you are correct. All mustangs except the 03-04 Cobras are solid axle rear ends.

I wouldn't tackle a gear swap if this is your first time, personally... Unless you are very confident in your mechanical skills. You're way better off having a shop do the work for you. Also do the math first. Get an idea of how much MPG you can gain by the swap, and then, with the current gas prices, see how long it will take you to recoup the money spent on the swap. It may or may not be worth it, especially since you already have 3.08's. There's not a huge difference between the two. I would also do the same with the driveshaft, you probably won't see much of a gain with it, and they cost a pretty penny.

bhazard 07-19-2008 05:31 AM

Im not positive but I think maybe my old fairmont project car has an even taller 7.5 gear than a 2.73. Like 2.47? I dont know. It was a 6cyl auto car. And they werent no quarter milers lol.

ALS 07-19-2008 03:46 PM

2.73's are too high for that set up. The best bet is to go to 3.08's from the 3.27's. The computer and transmission are already set up for the 3.27's.
You go to 2.73's you will take your car way out of it's power band and confuse the transmission of where it should be shifting. Don't you love computerized cars we have today. In most cases, you noticed the word MOST the automobile manufactures drop the optimum gearing by a set to improve the acceleration. It is the happy medium between fuel mileage and drive ability that is built into the cars today. It's like tire pressure.
They recommend 34 psi for the ride although 40 psi would be much better for fuel economy. There is always a compromise.
Around town there will be a minimum improvement in fuel mileage but expect between 1 and 2 mpg better on the highway. The trick is to incorporate multiple improvements to maximise the fuel mileage gains.

Big Dave 07-19-2008 07:41 PM

Having done the gear swap thing (3.73 to 3.08) I can tell you it is effective. I gained 3 MPG from doing it. But I have a diesel known for its huge low-end torque.

Before you do a gear swap, I'd recommend a long talk with an automatic transmission expert. A numerically lower rear end will slow down your torque converter and reduce ATF flow through the cooler, attenuating cooling. In a pickup, this leads to spectacular transmission failures - parts and fluid scattered down the road. Been there, done that.

cfg83 07-19-2008 08:07 PM

ALS and garys_1k -

Quote:

Originally Posted by ALS (Post 45611)
2.73's are too high for that set up. The best bet is to go to 3.08's from the 3.27's. The computer and transmission are already set up for the 3.27's.
You go to 2.73's you will take your car way out of it's power band and confuse the transmission of where it should be shifting. Don't you love computerized cars we have today. In most cases, you noticed the word MOST the automobile manufactures drop the optimum gearing by a set to improve the acceleration. It is the happy medium between fuel mileage and drive ability that is built into the cars today. It's like tire pressure.
They recommend 34 psi for the ride although 40 psi would be much better for fuel economy. There is always a compromise.
Around town there will be a minimum improvement in fuel mileage but expect between 1 and 2 mpg better on the highway. The trick is to incorporate multiple improvements to maximise the fuel mileage gains.

Without knowing the nuts and bolts of it, that's what I was afraid of. Unless you can also override the ECU/PCM with some kind of "manu-matic" paddle-shifter arrangement, I would think you'd have lots of shifting problems.

Quote:

garys_1k writes :
...

Of course, if you could recalibrate the shifts to work at the same vehicle speeds, then you'd be more likely to gain in city driving, too. I'm not sure how it's now calibrated -- to work off real vehicle speed or transmission output shaft (driveshaft) speed. If it's the latter than you'd definitely just delay upshifts with a lower numerical final drive.

...

Can this be done? At least for a Mustang, I would think there is more aftermarket options for something like this.

CarloSW2

garys_1k 07-21-2008 11:27 AM

Hmm, I don't know if an aftermarket shift point recalibration tool is available. I'd guess there is, given the popularity of Mustangs and the interest in performance modifications.

Again, though, if you did swap the axle you'd be guaranteed a nice highway FE boost, and even without a recalibration you'd at worst stay about even in around town driving. I'd go for it if you did at least 1/3 of your driving on the highway.

lovemysan 07-21-2008 12:27 PM

I would think that 2.73s would be fine. The 3.8 makes plenty of torque.

Tony Raine 07-21-2008 04:26 PM

Quote:

how can I improve acceleration without using 2GPH at 1365RPM when staring off at a dead stop without hitting the accelrator hard at all.
getting taller gears will make this worse. lower gears multiply torque (at a lower rpm) to make it easier to get moving.

Quote:

Would changing my Mustang's stock 3.27 rear gears to 2.73 increase my fuel economy and by how much possible?
i would count on about a grand+ to have someone swap the gears. (cost of gears, installation parts, oil, labor, speedometer correction, etc....). think you'll get enough out of this mod to pay for/profit from it? it will probably only drop your cruising rpm's by around 450. you can lower your rpm's a little by buying a little bigger tires for the rear once your stock ones wear out. (i got 2" bigger tires and dropped my cruising rpm by around 250.) but then you still have to correct the speedometer/odometer ( i just calculate after-the-fact).




lets say you get a 2mpg highway boost with the gear swap. assuming 15,000 (highway-only) miles a year and 3.90 for gas, you'll save $161 a year. so it will take around 7 years just to pay off the mod.

worth it? i'd say no. but thats just my opinion, which with $0.50 will buy a cold cup of coffee. if you still want to go through with it, you may be able to find an entire axle from another 'stang and swap it in. (unbolting an axle and bolting in another identical one is 1000X easier than attempting a gear swap youself). you may even find someone that will trade axle-for-axle because they want the lower gears.

whokilledthejams 07-21-2008 05:26 PM

If you can get a decent 2.73 rear axle for cheap (which I can't see being too hard), swapping out an entire axle is something you could do in a day in your driveway. Bribe a trustworthy friend with beer and pizza, and you're in business. Of course, I say trustworthy, because you don't need an axle dropped on your skull.

As for shift points, is it an electronically controlled transmission? If it isn't, it's probably not too hard to adjust, as it would all be mechanical adjustments. Again, something you could do in the driveway.

Schwaebz 07-21-2008 06:16 PM

for your case, i say you start here

3.8 Mustang Message Board - Powered by vBulletin

this is where you should mingle lol

Schwaebz 07-21-2008 06:22 PM

wikipedia

dcb 07-21-2008 06:23 PM

re: costs, if you are a do-it-yourselfer AND you know what prussian blue is (not the little singers from hell), then you can probably pluck some better gears out of a boneyard rearend for like $20.

Schwaebz 07-21-2008 06:31 PM

lol, if its a GT that the op has, i will slap you for trying to through a 7.5 on there, i frankly woulkd try other options for your car. try lighting it up, throw a dual exhaust on it, a CAI, under drive pullies, lower it, get some nice wheels on it


and bam, you'll have a decent car


plus, you will somehow have to re calibrate the car, since it will be a different gear ratio, which costs a lot of money

i say, go to the website i gave you, and give in to the dark side of the force

dcb 07-21-2008 06:47 PM

Dual exhaust for MPG?!? I'm goin to say "try the friggin search button" at this point in the discussion :)

But If I didn't want to pay for a new car and title and crud, I would swap the rearend gears and put in a stickshift all with the lowest ratio I can find, but no way I would pay someone to do it. Fortunately a lot of performance bent folks will just about give that stuff away.

Blue07CivicEX 07-21-2008 07:05 PM

So... why aren't you out racing people, burning your tires, playing 80's hair bands and getting laughed at by all the people on this site instead of trolling "hippy" forums to make fun of people trying to save a buck? The world is full of people that like to spend their money elsewhere then in the gas tank, people have kids, mortgages, other hobbies they would prefer to spend their money on.

In closing, don't be a dick, if you're here to troll find a better hobby, I'd rather be considered a hippy then be considered whatever you think you are.

Tourigjm 07-21-2008 07:31 PM

Quote:

Originally Posted by Moonbaby (Post 46189)
yay. because i don't need a forum to show me some insight that spending massive amounts of cash to save a buck or two is pointless.

So why are you here?

In just about every post you call the OP or someone that replies to it an ignorant hippie.

For some people spending the extra money to make their car stretch the mpg's makes sense. people who own their cars, who aren't going to sell them, and who are going to make their money back in fuel savings in about a year (Lookit basjoos)

Personally I'm not going to be modifying my car, I plan to sell it in ~2 years, however if i can turn :turtle: into a competition it makes it that much easier to drive 55 on the highway.

Not everyone on this board is a hippie. Most are here because they want to make a difference either in their wallet or in their environmental impact. AFAIK Hippies spend more time complaining about "The Man" keeping them from smoking weed... thats a real waste of cash if you ask me.

Schwaebz 07-21-2008 07:40 PM

Quote:

Originally Posted by dcb (Post 46171)
Dual exhaust for MPG?!? I'm goin to say "try the friggin search button" at this point in the discussion :)

free flowing exhaust anyone? no point having the exhaust system bottle up the cars engine, let er breath:thumbup:

plus, dual exhuast looks amazing on a mustang:D

NeilBlanchard 07-21-2008 07:40 PM

I'm invoking Godwin's Law.

I guess we all cannot be as clever and imaginative as you are Moonbaby?

Schwaebz 07-21-2008 07:44 PM

and back on the gears, i suggest you dont change them out, a gear change done by a professional is roughly $300, or more, plus, your engine wa sdesigned to work with those gears, it was made to go wiht them hand in hand, so dont blow off one of the hands fingres

2000mustang fan 07-21-2008 07:50 PM

Quote:

Originally Posted by Tourigjm (Post 46214)
So why are you here?

In just about every post you call the OP or someone that replies to it an ignorant hippie.

For some people spending the extra money to make their car stretch the mpg's makes sense. people who own their cars, who aren't going to sell them, and who are going to make their money back in fuel savings in about a year (Lookit basjoos)

Personally I'm not going to be modifying my car, I plan to sell it in ~2 years, however if i can turn :turtle: into a competition it makes it that much easier to drive 55 on the highway.

Not everyone on this board is a hippie. Most are here because they want to make a difference either in their wallet or in their environmental impact. AFAIK Hippies spend more time complaining about "The Man" keeping them from smoking weed... thats a real waste of cash if you ask me.

I completely agree with you. I agree with repacing the stock rims with larger wheels, sadly it's already been done because stock they are 15" mine are 17" Im not sure if the preevious owner re-calibrated the computer. I have true-dual exhaust already on this car. Basically put all the small modifications like that are done, that's why I'm either going to go with tranny swap or swapping out gears, although from what I've heard about changing the gears the Tranny swap sounds alot more worth it right now. I got my scangauge and I can already see the improvement on my driving habbits I got ~200miles with 7Gals of gas I'd say I'm doing good but I eant to know how much more I can get out of it. My aero modas aren't even done so I expect an even greater increase by the end of this year I plan to have this car squeezing out about 27MPG AVG. I'm close but not close enough. I don't want big oil to steal all of my cash thank you very much for the guy on here calling me a ippy for trying to save gas, and thanks to the people who are agreeing with me as I agree too gas costs way too much. If big oil wants to try and put us down, well this is the way to fight gas prices.

lovemysan 07-21-2008 08:11 PM

Quote:

Originally Posted by 2000mustang fan (Post 46235)
I completely agree with you. I agree with repacing the stock rims with larger wheels, sadly it's already been done because stock they are 15" mine are 17" Im not sure if the preevious owner re-calibrated the computer. I have true-dual exhaust already on this car. Basically put all the small modifications like that are done, that's why I'm either going to go with tranny swap or swapping out gears, although from what I've heard about changing the gears the Tranny swap sounds alot more worth it right now. I got my scangauge and I can already see the improvement on my driving habbits I got ~200miles with 7Gals of gas I'd say I'm doing good but I eant to know how much more I can get out of it. My aero modas aren't even done so I expect an even greater increase by the end of this year I plan to have this car squeezing out about 27MPG AVG. I'm close but not close enough. I don't want big oil to steal all of my cash thank you very much for the guy on here calling me a ippy for trying to save gas, and thanks to the people who are agreeing with me as I agree too gas costs way too much. If big oil wants to try and put us down, well this is the way to fight gas prices.

If it was my car I'd swap the gears the cheapest way possible. Which would probly involve a junkyard axle and evening with air tools. My current car has a .61 overdrive gear. Which puts it at peak torque at 70 mph 2450rpms. But I generally drive 55-60mph. Were talking LOW hp here. With the a/c on 50-70mph accelleration in top gear is around 30 seconds or more. You could probly get away with 2.56 gears. A stock roadmaster does.

Tony Raine 07-21-2008 08:57 PM

alright, since the trolls have been banned, lets continue..........

if you have the mechanical skills to do it yourself, a stick shift swap may be beneficial. but only if you can sell the automatic to recoup the loss (as far as i know, an automatic cost more than a standard).


back to tire swapping, my switch from 29" tires to 31" tires is the equivalent of swapping from my 3.73 gears to 3.49 while keeping stock tires. i've run this tire size for around 2 years and have had no transmission problems (related to tire size).

i think rear tire swapping would be a good way to "test" to see if your car can handle "taller gearing" before making the jump to actual taller gears. (since tires are a wear item and are replaced, but gears usually aren't.

whokilledthejams 07-21-2008 09:15 PM

Ah, "performance enthusiasts."

That is to say, people who huff paint, apparently as their occupation.

I like Tony Raine's idea of taller tires as a test for gearing changes. It's easy enough to do. I personally can vouch for a modest tire size change helping MPG by changing the gear ratios.

Either way, changing out the rear end isn't going to cause any problems. Ford's Fox platform is the automotive equivalent of Legos, so it's easy enough to swap rear ends (and transmissions and engines) around.

Tony Raine 07-21-2008 09:34 PM

Quote:

Ford's Fox platform is the automotive equivalent of Legos, so it's easy enough to swap rear ends (and transmissions and engines) around.
:D never heard it referred to that way, but yeah, thats about right.

is the 2000 still on the fox platform, though? i thought they strayed away from it around '95.

wagonman76 07-21-2008 09:53 PM

Id try swapping some larger tires on just to see how it does. Thats a great idea as long as they fit.

And if it proves well, Id bolt on a junkyard rear axle assembly rather than try to change the gears themselves. Ive read a lot about changing gears in the RV towing forum and usually it requires setting up precise clearances with shims, if its not done right youll burn up the gears in short order. It takes a pro to do it right which costs quite a bit. Then too if you ever want to go back, just bolt the rear axle back on. You might also have to reflash the computer, or get a VSS signal adjuster box, Im not totally sure.

My take on it is to try to get the most distance out of your available torque, without having to downshift. I would think a Mustang would have gobs of leftover torque that is reserved for performance driving. Change the rear end and you probably wont be able to burn the tires, but youll get farther down the road instead. Now if you change the gearing so far that you end up having to downshift on mild grades and headwinds, then its not worth it.

2000mustang fan 07-21-2008 10:18 PM

Quote:

Originally Posted by Tony Raine (Post 46281)
alright, since the trolls have been banned, lets continue..........

if you have the mechanical skills to do it yourself, a stick shift swap may be beneficial. but only if you can sell the automatic to recoup the loss (as far as i know, an automatic cost more than a standard).


back to tire swapping, my switch from 29" tires to 31" tires is the equivalent of swapping from my 3.73 gears to 3.49 while keeping stock tires. i've run this tire size for around 2 years and have had no transmission problems (related to tire size).

i think rear tire swapping would be a good way to "test" to see if your car can handle "taller gearing" before making the jump to actual taller gears. (since tires are a wear item and are replaced, but gears usually aren't.

The tranny swap is looking to be my best bet. I can probably sell off the automatic somewhere because it is in excellent condition with only 66,000miles on it so it should still be worth about a grand or two considering a new automatic trans costs about $5k.

whokilledthejams 07-21-2008 10:27 PM

Quote:

Originally Posted by Tony Raine (Post 46301)
:D never heard it referred to that way, but yeah, thats about right.

is the 2000 still on the fox platform, though? i thought they strayed away from it around '95.

Ford Fox platform - Wikipedia, the free encyclopedia

The '04 Mustang was the last derivative of the Fox platform, though it was somewhat modified after '94. You can, as far as I know, still swap much of the drivetrain of an '04 Mustang into, say, a '78 Fairmont with relatively little drama.

I remember hearing that leading up to the release of the current ('05+) Mustang that it was the first complete redesign in over 25 years, so that makes sense.

lovemysan 07-21-2008 10:40 PM

The Sn95 94-98 has a narrower rear end by 3" but otherwise is similar to the 99-04 rear end. This refers to the 8.8".

reformed 07-22-2008 08:31 PM

Quote:

Originally Posted by whokilledthejams (Post 46320)
Ford Fox platform - Wikipedia, the free encyclopedia

The '04 Mustang was the last derivative of the Fox platform, though it was somewhat modified after '94. You can, as far as I know, still swap much of the drivetrain of an '04 Mustang into, say, a '78 Fairmont with relatively little drama.

I remember hearing that leading up to the release of the current ('05+) Mustang that it was the first complete redesign in over 25 years, so that makes sense.

Haha, even though it still might be considered a fox platform, they aren't that easy to swap parts like that from year to year. 79-93. 94-95. 96-98. 99-04. Are where you get the different designs, each with their little tweaks that make swaps to different styles, not impossible, but sometimes difficult and not cost effective. I've built a few mustangs in my day (All Foxes), and I've been involved with a transplant of an 03 4.6 Cobra powerplant into a 89 mustang and believe me, there was drama! When swapping parts and trying to stay cost effective in a mustang, its better to stick with your style mustang for most parts, or at least make sure to cross reference first. They did change the axle length also from 93 (foxbody) to the 94 (sn-95) year and I'm not sure if it stayed the same after that or not.. other than the 79-93 model years, my knowledge of mustangs drops off quite a bit.


All times are GMT -4. The time now is 05:18 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com