going for lower gears 3.23 down to 2.73

J

johnnyboy1111

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Jul 19, 2005

#1

• Jul 19, 2005

• #1

I'm using my 99GT auto for just long trips , she has well over 160,000 I drive alot & she is still running like new changing oil every 2,000 , being gas is close $2.75 for reg I was thinking of swapping for maybe 2.73 or lower gears ....my 90 notch could get 30+ on the open road , the best the 99 ever gets is 22 or 23mpg......think I will have any problems , computer or tranny shifting ? anyone out there ever done it ? PS please dont tell me to buy a econobox I like my Stangs ....thanks ..........................Johnnyboy

 

wannabe2000GT

New Member

Nov 9, 2004

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upstate, ny

Jul 19, 2005

#2

• Jul 19, 2005

• #2

just pay the gas everyone else does. or just buy a v6 mustang

 

billfisher

Active Member

Jul 17, 2005

1,296

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huntsville, AL

Jul 19, 2005

#3

• Jul 19, 2005

• #3

I get 27 mpg @65 with cruise. no air.

 

tomustang

Psychotic Member

Founding Member

Jun 8, 2000

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McLean Hospital

Jul 19, 2005

#4

• Jul 19, 2005

• #4

Stock is 3.27, not 3.23

You're not going to see dramatic improvements in lowering the gear

You will see better improvememt if you buy a different tranny with an optional gearing set.

 

billfisher

Active Member

Jul 17, 2005

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huntsville, AL

Jul 19, 2005

#5

• Jul 19, 2005

• #5

ultimate mpg gt???

do the gear change go to small maf(55mm) and small injectors, change to 15 in rims with 175/80r15 tires. lower the car 2 in. run high pressure in the tires. drive 55mph with cruise, no accesories running... or buy the equivalent taurus.

 

billfisher

Active Member

Jul 17, 2005

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Jul 19, 2005

#6

• Jul 19, 2005

• #6

you HAVE to reflash the computer. your speedo is electronic.

 

DBMSTNG

I fantasize about it being BIG!

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Apr 23, 2002

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Jul 19, 2005

#7

• Jul 19, 2005

• #7

you may actually lose gas mileage by swapping to a taller gear.

it's not worth the time, money, or effort.

 

trinity_gt

10 Year Member

Jan 31, 2003

3,125

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99

Canada

Jul 19, 2005

#8

• Jul 19, 2005

• #8

Yeah, 4th (OD) with 3.27s is already a pretty tall combo. Just how low do you expect the engine to rev and not require quite a bit more throttle to pull the gear (i.e. lugging?)

The fuel mileage problem with the Mustang comes largely from two sources: lousy aerodynamics and rolling resistance. Yours being an auto doesn't help either...

If the cost of fuel is truly a concern than a V8 Mustang probably isn't the best car to have. I know you asked us to refrain from the "econobox" suggestion 'cause you like your Stang but there's not a lot of options. A V8 Mustang is a gas guzzler. Enjoy it and get lousy gas mileage if you like it or get a 4-banger import if you want fuel mileage. I don't think you'll get both with this platform.

 

billfisher

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Jul 17, 2005

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Jul 19, 2005

#9

• Jul 19, 2005

• #9

fuel economy is a function of rolling resistance,aero,and drivetrain. Gearbox drag,differential drag, and engine parasitic losses are a sigificant source. If 2.73 is so bad and will cause problems then why was it standard for so many years. you will still be able to pull hills and coast at very low rpms. Low RPM's equals lower parasitic drivetrain losses. Just look at rear wheel HP losses to illustrate this fact.

 

billfisher

Active Member

Jul 17, 2005

1,296

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huntsville, AL

Jul 19, 2005

#10

• Jul 19, 2005

• #10

tire width is another source. narrow high pressure tires are used on the front of drag cars for a reason. Rolling resistance. 175-15''s sound funny, but they save gas. change them back to wides for fun.

 

billfisher

Active Member

Jul 17, 2005

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huntsville, AL

Jul 19, 2005

#11

• Jul 19, 2005

• #11

dropping the car 2" reduces the frontal area by a function 2"X total width around the top of the car. (a large number). also closing the fake intakes in front of the rear fenders (aerodynamically) will help. ramp them closed

 

dollarbill

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May 5, 2005

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Decatur, IL

Jul 19, 2005

#12

• Jul 19, 2005

• #12

I would start by giving the car an entire tune up. Plugs, wires, clean maf, iac, etc...Also change all your fluids over to synthetic, they will help with your rolling resistance. Also a drop in K&N and some underdrive pulleys will help. Tire pressure can also help, up it to 35 psi cold instead of 30. If this stuff doesn't work trade it in on a nice V6 Mustang or just live with it.

 

mustang70

Founding Member

Nov 15, 2001

2,445

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48

San Diego

Jul 19, 2005

#13

• Jul 19, 2005

• #13

Am I the only one that thinks my car gets good gas mileage? I'm very happy with the 20-21mpg I get. And that's coming from a Mazda that could get 30mpg.

 

04DarkShadowGT

Member

Jan 31, 2004

474

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Fort Wayne, IN

Jul 19, 2005

#14

• Jul 19, 2005

• #14

Get a second beater as a DD.

 

J

johnnyboy1111

New Member

Apr 27, 2004

84

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Jul 19, 2005

#15

• Jul 19, 2005

• #15

thanks for the input

thanks guys it was just an idea , when the gas prices pass $3.00 you may start getting ideas of your own ......auto insurance is also another pain so getting extra cars as DD is just a drain .... I do keep it A-1 , syn oil , 35lbs tire pressure,20mpg is still not bad ..... to be honest I dont see the gas or economy getting better any time soon , the people with those monster SUV's are really hurting even in Florida every 4th or 5th auto was an SUV & they dont even get snow? one guy was telling me at the pump he was spending $90 every 5 days in gas in his SUV

 

DBMSTNG

I fantasize about it being BIG!

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Apr 23, 2002

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Jul 19, 2005

#16

• Jul 19, 2005

• #16

billfisher said:

If 2.73 is so bad and will cause problems then why was it standard for so many years.

Click to expand...

no one said it was "so bad", so don't put words in peoples posts. but anyway, emmisions most likely. people have reported and increase in mileage by switching to 3.27's from 2.73's. it's not any different than 5spd owners reporting getting better mileage at certain speeds in 4th rather than 5th.

 

CanadaStang

New Member

Sep 7, 2003

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Mb

Jul 19, 2005

#17

• Jul 19, 2005

• #17

billfisher said:

fuel economy is a function of rolling resistance,aero,and drivetrain. Gearbox drag,differential drag, and engine parasitic losses are a sigificant source. If 2.73 is so bad and will cause problems then why was it standard for so many years. you will still be able to pull hills and coast at very low rpms. Low RPM's equals lower parasitic drivetrain losses. Just look at rear wheel HP losses to illustrate this fact.

Click to expand...

Lower rpm's doesn't always equel better mileage. Changing to 2.73's may not change the mileage much, or may even actually decrease the mpg. The 2.73's worked well with the 5.0 Stangs, as the 5.0 had alot more low end torque than the 4.6's. At roughly 1500 rpm [60mph with 2.73's] the 4.6L engine will be working far harder at 60mph than with the stock gearing. As an example, when going into a head wind, my 2.8L Blazer gets far better mileage in 4th than in 5th. Although the engine is turning lower rpm's in 5th, it's working too hard to take advantage of the taller gear.

 

C

CrazyHorn

New Member

Jun 14, 2004

184

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Gatineau

Jul 19, 2005

#18

• Jul 19, 2005

• #18

If you cant afford your car anymore than sell it and buy a toyota echo or a civic.
I think you should get better mpg on the highway than that doh, with my 02 5spd I got 30mpg on the highway, its pretty good for a v8. Maybe she just needs a tuneup.