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Discussion Starter · #1 ·
I have a 2001 GT 4.6L Automatic convertible 315/45/17 (3.55). I was wondering what ratio I need to go with. I am concerned out the increase of rpm's, milege decrease but I would like to compromise. What are my options and what will I expect from the change? Thanks for your imputs.
 

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Do the 4.10s and dont look back. I did and it totally woke up my car, an 03 auto vert. You love it and believe me it still wont be enough! I am not sure my exact milage but I get about 210 miles per tank (suburbs driving, to work and back) whereas I used to get 215 to 220.
-Lee
 

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Gears

I have 410's in my vert gt,18-20 mpg every time, 14 gallons is 260-280 miles
but i went from 373 to 410 and didnt notice alot
if not mostly for hiway id go 430 or 456, then bump up to a 28 in tall m/t drag radial
btw, i punish this car
ken
 

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Off hand i would guess 80mph 2200-2400 range, 65mph 1800-2000
next time im on the hiway i will make note and update
ive been mostly driving my mach1 and its diff. 355's 5 spd
 

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I'm in the same boat I wanted the 4.10 for performance but I also drive a lot of highway miles and didn't want to sacrifice my gas mileage too much. I couldn't decide between the 4.10s or 3.73s so I compromised and just ordered a set of Motive Gear 3.90s for my 04 GT coupe auto. Stage 3 Motorsports had the best price on Motive gear 3.90s I paid like $189 with free shipping. Everyone else wants like $220 plus for them. RPM wise it should run just under 2700RPM at 75 MPH which is acceptable to me.
 

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does the computer need to be flashed when changing the gears & say you wanted to go the other direction for good MPG my older 1990 5.0 would run under 2,000 rpm at 80 mph it got excellent mpg 28 mpg .....my 1999 GT mpg the best I ever got was 23 mpg ......its a daily driver my racing days are long over
 

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Discussion Starter · #10 · (Edited)
My convertible weights 4490 lbs and wondering what regular mustangs weight virus mine. I am thinking of gear sets 3.90, 4.10 and 4.30 are the choices for me. I am leaning toward the 4.10 but the weight of the convertible is what causing a back step. I know that I will need to flash computer to accommodate for the different shift points. What programer to get for this? SCT live wire or something else?


MikeMike, I don't think you want to put taller gears in your mustang. Maybe a six speed trans is the way to go. I have been thinking about switching over to manual but I would put a six speed if I go that route. Money is the issue for me but if I had the cash it would already done.
 

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4400 lbs for a Mustang ? seems kind of off ! converting to stick too much the old gal has over 160,000 miles I have a feeling this gas price thing will not go back this time I can live with 20 mpg , I drove a new 5.0 at the dealer with the 6 speed auto & mild rear ratio they claim great mpg like the Corvette it was just a thought I must say the 4.6 is a great motor , that new 5.0 seems OK but time will tell , the price was $36,000 out the door base 5.0 no brembo or other stuff , I spent the whole winter in Florida & saw many more Camaros , most of the Mustangs were 6 cyl very few 5.0 ....
 

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Discussion Starter · #12 ·
4490 lbs is what in the drivers door. I thought it was heavy for a mustang but not sure if that is correct.
 

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4490 lbs is what in the drivers door. I thought it was heavy for a mustang but not sure if that is correct.
The drivers door tag is the Gross weight of the car, meaning how much weight the car can hold including the weight of the car itself !

Your Mustang is in the 3400+lbs range
 

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I have spent a lot of time deciding what gear to run. I do quite a bit of high way driving. I think everyone will agree 4.10's are the best seat of the pants feel! But in the real world of commuting in a daily driver like me. They may not be the best for your commute, 4.10s will put you at 2830 RPM at 75 MPH and 3025 RPM at 80 MPH so the math says in OD and converter locked. That is not acceptable for my commute! I went with 3.90's a nice comprimise between 3.73's and 4.10's. How ever you may actually pick up mileage if you do a lot of around town or city driving. It is really up to you and your driving style I guess.
 

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Also I calculated with a stock 25.7" tall tire. I'm sure others running 4.10's with an auto will confirm my numbers are very close to what they are actually seeing on their tachs at those speeds I stated above.
 

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I have used 327s, 373s, and 410's....if you are a track guy looking for the edge running DRs then 410s are the way to go...if you are looking for performace with the best gas miliage you can get use 373s with your auto......I got 23-24 mpg with the stock 327s and 23 mpg with the 373's......with 410's it dropped down to 17 city and 19 highway......and when I played hard as low as 15 mpg.....with the new TFS heads I get 20-21 mph with 410's.....I will be going back to 373s when the blower is on the car and should be in the 24-25 mpg range with the TFS set-up.....hope this helps...

"ED"
 

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Ed,
Where were you when I was looking for mileage info? Lol. I did my own math and quickly found out that 4.10's weren't going to work for my highway commute as much as I wanted them for performance. But in these times the price of dinosaur juice made me compromise down to the 3.90's.
 

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It depends, are you going from 5.14's to 4.30's? LOL. It all really depends on what you want out of it, how and where it's driven.
 
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