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I have a 2003 gt as of now my daily driver do a lot of highway driving to and from work everyday so for now gas mileage is kinda important. I'm wondering which would be the best gear to go with I will going fi this summer
 

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Loud Exhaust Enthusiast
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I'd say go with 4.10 even with FI. That will put you around 400rwhp if you crank it up. I'm a bit above that with 4.10s (given, we have different trannies) and I love them. 3.73's would be a waste of time and money. I'll let someone else chime in though.
 

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Head Unicorn
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I'm always going to suggest 4.10s. Always. If you're going to commute 50 miles one way at 90+ mph 4.10s are not the best choice. I rarely travel at over 75 mph on the interstate and I spend the majority of my time on a track and not on a street. I may have put 500 miles on mine last year. 3.73 doesn't make enough of a change for my taste, just my opinion though.
 

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I have a 2003 gt as of now my daily driver do a lot of highway driving to and from work everyday so for now gas mileage is kinda important. I'm wondering which would be the best gear to go with I will going fi this summer
Stock 3.27's if you're worried about fuel.
 

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4:10 gears are fun to have, but you will lose MPG. Example. friend and I both have same car. We went from TX to FL. He got about 26mpg (stock 3:27 gears) I got about 21MPG (4:10 gears) We both have T45 tranny.. I just switch to 3:73 from 4:10 due to the new HP I have.. +600HP and 4:10 gears = not very good tractions. Now with 3:73, I can stay in 1st gear alittle longer before shifting and have very little traction issues. I also have UCA and LCA, with DR tires..
 

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Discussion Starter #7
Not really concerned with fuel that much just wondering mainly the rpms I would be turning at 70mph. I no I'm gonna loose some mpg
 

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What's the final gear ratio on a 3650? I'm running stock 2.73's with a .82 final gear and my RPM's stay around 2400 at 70mph.
 

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Not really concerned with fuel that much just wondering mainly the rpms I would be turning at 70mph. I no I'm gonna loose some mpg
do a lot of highway driving to and from work everyday so for now gas mileage is kinda important.
Looks like it is. Anyway 4.10's.

What's the final gear ratio on a 3650? I'm running stock 2.73's with a .82 final gear and my RPM's stay around 2400 at 70mph.
Stock gears for 99-04's are 3.27's.
 

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Not really concerned with fuel that much just wondering mainly the rpms I would be turning at 70mph. I no I'm gonna loose some mpg
I have 4.10's on a supercharged daily driver. I rarely do any highway. It's all city street driving. At 75mph you'll be around 2600rpm.
 

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Anandavenkatakrishnan
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Not concerned wit fuel you say?

4.30's :shiftyeyes
 

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Stock gears for 99-04's are 3.27's.
Hmm, something is aloof. I thought I had read somewhere that 3.27 was an option, which obviously isn't the case. I went out and checked my rear end tag and it shows 3.27 as well. However, the RPM calculator is showing a much higher number with 3.27s vs 2.73s. With 2.73 gears calculated, the RPM is almost exactly what my tach is reading at 70. :dunno
 

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Count tire and Drive shaft rotations and divide to see what ratio you have. Don't trust the tag all the time.
 

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'sup homies
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What's the final gear ratio on a 3650? I'm running stock 2.73's with a .82 final gear and my RPM's stay around 2400 at 70mph.
I used .68 for overdrive on that calculator in my previous post. I believe that's stock O/D for T5/T45/TR3650 and .82 is for close ratio or WC trans.

I may be mistaken, if I am, someone please correct me
 

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Overdrive for an auto is .70:1, for a T-45 its .67:1, for a 2001 T-3650 its .68:1, and for a 2002-2004 T-3650 its .62:1. With your higher overdrive gear ratio you will be going down the highway with 4.10s at approximately the same rpm as I do with 3.73s. At 70 mph my car is running around 2350 rpm. Yours should be around 2400 rpm.

Most of the people who run superchargers do not run 4.10s. Last year there was a tread about mods and track times. Of the 23 respondants only 6 ran 4.10 gears. Even with 3.73s and 315/35 drag radials, first gear is nothing but a tire shredder. At a 20-25 mph roll if you push the pedal to the metal the tires break loose and you bounce off the rev limiter. In second the tires break loose but then grab a little later. With 4.10s traction will be a problem in both first and second. There have been several forum member swap out 4.10s for a higher gear after going FI.
 

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I Need More Power!!!
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So with 3.73s ill be around 2300 at 70
I have 3.55's right now and im at about 2100/2200 rpm range, so that sounds about right. I will say this, the drone from my 40 series sucks so bad at that RPM range. I want to step up to 3.73's or 3.90's just to get rid of it. I would personally recommend 3.73's since you are FI, would like to retain some gas mileage, and probably would like 1st to remain useable.
 
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