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Discussion Starter · #1 ·
Thinkin bout upgrading from the auto (5 speed) GT's 3.21's to 3.73's, am running 91 SCT tune, 20" wheels(came w/ car) and CAI, drive mostly in city, not much long road trips.
 

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Discussion Starter · #4 ·
As soon as these tires(new) wear out, that's the plan, prob. 18" ers :cool:
 

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I would do the 4.10's as well. My son's new edge GT has 4.10's and it's amazing the difference in the launch between his car and my stock gear GT.
 

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I've ridden in Revvv's 02 GT with 3.73's. If I may be so bold as to say so, and I think he's said the same, my stock 3.27 auto seemed to pull a good deal harder than the 5-speed 3.73's. Most people do 3.73's w/5-speed, and 410's w/auto. From my experience, I'd go with 4.10s in the 5 speed, and 4.30-4.56's in an auto. I personally will be going 4.30's or 4.56's in my auto.

Both of our cars are tuned for 93, and stock. Well my motor is stock, I do have an o/r exhaust. Cars are close enough that I think the comparison is accurate enough though.

Really, I think you may be disappointed once you've experienced the 3.73's. Can you find some people with both and go for a ride?

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The difference between ratios is the same, and we are talking about a fairly similar automatic.

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You will see a difference in mpg. Just to give you an idea. When my son burns a tank in his 2000 GT I still have 1/4 tank of gas left in my 1999 GT.

At Project Pony - in my 69 Mach I, I installed a bullet proofed AOD behind a 427 stroker (500+ rwhp) and changed the rear to a 4.56 Detroit Locker. After factorying in the final drive ratio I ended up with basically 3.73 in overdrive which is very reasonable on the highway, but it's nasty stop light to stoplight. 😈 Tons of fun to drive.
I know we're talking about different years and hardware, but I think you will be very pleased if you use the 4.56 setup (provided this is not a daily driver).
 

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Discussion Starter · #12 ·
You will see a difference in mpg. Just to give you an idea. When my son burns a tank in his 2000 GT I still have 1/4 tank of gas left in my 1999 GT.

At Project Pony - in my 69 Mach I, I installed a bullet proofed AOD behind a 427 stroker (500+ rwhp) and changed the rear to a 4.56 Detroit Locker. After factorying in the final drive ratio I ended up with basically 3.73 in overdrive which is very reasonable on the highway, but it's nasty stop light to stoplight. ������ Tons of fun to drive.
I know we're talking about different years and hardware, but I think you will be very pleased if you use the 4.56 setup (provided this is not a daily driver).
It is a daily driver, smogged etc, is why I am leaning to 3.73's for a 06 4.6 auto, CAI w/ a 91 Bama/XCT/Mustang Evo tune
 

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Daily, and auto, the difference in fuel economy is negligible at best. 1-2 mpg, but that's usually the heavy foot with new found acceleration. 94-09 cars love gear, I'm not as familiar with how the older cars like gear.

My car sees highway occasionally, it will still be getting 4.30's+. That may be a tad more than most would want, but definitely OP, you should go to your local Mustang Club and I'm sure someone would take you for a ride to compare different ratios. I've talked to quite a few people who went with the 3.73's in the auto, and ridden in a few, there is such a small, hard to notice difference between the stock and 3.73 (auto) ratio. Most are disappointed, some end up spending more money to go 4.10+.

Everyone has thier opinions. Mine, no less than 4.10 in a 3v auto. But the next guy might like it. Again, the single most helpful thing you can do for yourself OP, is ride or drive in a few, and decide for yourself what you actually want and can live with. Cheers!

Ps. My 1990 YJ had 5.56's, and when I would let off the clutch it would climb straight up a wall it would seem with no input from the throttle! Though you could change lanes in it shifting from 1st to 2nd. I love gear!

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I agree. Mo gear mo better. Mpg really not that bad unless you keep the accelerator matted most of the time. Regular driving should be ok. But your best bet is to ride/drive someone's car that has that gear and see what you think. After all it really comes down to your own personal preference.
 
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