07 GT's now have less performance

YardSpecial · Oct 6, 2006

2 wheel peel !!

metroplex said:
Do the 3.31s come with a factory LSD or an open differential?

Last time I checked, all 05-06 GT cars had LS rears. No open diff was STD

srothfuss · Oct 6, 2006

The original question was the difference between 3.31's and 3.55's? That might be like 200RPM's or somewhere in that neighborhood. I'd have to calculate it out, but I don't think that change will hurt overall performance.

My car will be a DD. As such the 3.55's will be all I need to get on the highway in the morning and on the highway in the evenings. But what am I saying - my car hasn't even come in yet!

313Speed · Oct 6, 2006

I still don't understand why people would go to A 4.10 on a 5 speed car. Seems like a waste of gas and a good way to stress the motor by keeping it reved up on the highway. 3.73 is should really be the choice if you're actually driving the car, and with 3.55's, the swap seems pointless.

metroplex · Oct 6, 2006

I made spreadsheets for the 4R70W and TR-3650 and srothfuss is right, there's about a 200RPM difference between the 3.31s and 3.55s at highway speeds.

Coincidentally, a GT with 3.55s will run at the same RPMs as a 98-02 Crown Vic with 3.08s.

xr8d302 · Oct 6, 2006

Not even from around these forum parts, but I would agree with anybody that's said 3.73's or 4.10's.

If you're looking for a whole new world of driving, go 4.10's and nothing less.

thump_rrr · Oct 6, 2006

YardSpecial said:
3.73 are my choice with a stick car, I like frewways too much..........
With a auto 4.10 or 4.30 are a must.

Blower car, 3.55 anything lower and you blow the tires away.........

Saleen S/C with JDM Stage II and 10psi (aprox. 460-470rwhp) running 4.10's and loving it.

YardSpecial · Oct 6, 2006

thump_rrr said:
Saleen S/C with JDM Stage II and 10psi (aprox. 460-470rwhp) running 4.10's and loving it.

Maybe for a drag car...........

Saleen is where I got my info from and I agree. Roots-Screw blower and 3.55 or 3.73 with heavy 18"-20" wheels.

05-07 trans have low geared first, so 1st gear would be usless

Just my thoughts playing with stangs since 1990 and still have lots to learn.

thump_rrr · Oct 6, 2006

YardSpecial said:
Maybe for a drag car...........

Saleen is where I got my info from and I agree. Roots-Screw blower and 3.55 or 3.73 with heavy 18"-20" wheels.

05-07 trans have low geared first, so 1st gear would be usless

Just my thoughts playing with stangs since 1990 and still have lots to learn.

I don't drag race on the streets so smoking first isn't an issue.
When you want to pass someone on the highway though drop it down a gear and it's gone.

rich8566 · Oct 6, 2006

BLK_2001_GT said:
I just purchased a brand new 07 Mustang GT. I love the car very much, but in reading some of the threads in here, I was extremly disapointed to see the 3.55 ratio for the manual transmission is now only available as an option. Not nowing that, the one I purchased aparently has the new standard 3.31 ratio.
(The 3.55 option is not listed on my window sticker)

My question: How much performance am I loosing with the 3.31 vs. the 3.55's?

How much is the cost aproximetly to change the ratio to 3.55 or 3.73 with parts and labor?

Thanks for any help suggestions you can offer.

Go for the 4.10s. That will provide 15% higher RPMs in all gears over 3.55s. That will be 24% higher RPM than your current 3.31s. I have a 5spd manual with 3.55s and I will be moving up to 4.10s.

Emay · Oct 10, 2006

I have an 07 gt and had the 3.31 as well. Didn't have the car two weeks before I bumped it to 4.10's. You will not get a bigger seat of the pants feel across the rpm range unless you bolt up a power adder.

These cars are asleep with the gramma gearing.

Fourth Horseman · Oct 10, 2006

timeless2 said:
Modulars love to rev and 4.10s will get you there. IMO, the bump to 3.73 with a 3v or 4v engine just isn't enough.

4.10s or bust!

Agreed. Going from 3.55 to 4.10 really woke up my Marauder. I imagine it'd be even a bigger felt improvement on a car that weighs 700 - 800 pounds less.

metroplex · Oct 10, 2006

Actually going to 4.10s on a 05-up GT is like going to 3.80s on a 98-02 Crown Vic in terms of RPM and highway speeds.

3.31s on a 05-up GT is essentially the same as 3.08s on a 98-02 Crown Vic.

I will skip the optional 3.55s and stick with the 3.31s for better gas mileage, higher driveline critical vehicle speed, and perhaps less chance of driveline howl.

MBDiagMan · Oct 10, 2006

Due to the fact that the 3V Mod motor has it's torque peak at a very high (for a street engine) 4500 RPM or more, going from a 3.55 to a 3.31 could actually use MORE gas depending upon your driving style.

This isn't the sixties any more. Then engines had torque peaks as low as 2500 RPM or less. REMEMBER, the torque peak is the most efficient RPM of any engine. Lower gears will run you closer to the torque peak providing better efficiency. Couple that with the fact that lower gears will get you to your top gear quicker.

SOOoooo...... in some cases, slightly higher (lower numerically) gears can net better fuel economy, BUT...... Not always!

metroplex · Oct 10, 2006

My 4.6L 2V V8 makes the most torque at about 4000 RPM. If I shifted at 4000 RPM, my gas mileage goes downhill fast (it'd be like driving near WOT all the time). SCT has tuned the 4R70W to shift at around 1500 RPM for max fuel economy with the 4.6L 2V V8.

My 2000 Vic has 3.55s and it keeps the RPMs pretty high compared to a stock Vic with 2.73s. The Vic with 2.73s gets 18-20 mpg city, 25-30+ mpg highway. The Vic with 3.55s gets 11-13 mpg city, 19-20 mpg highway.

BLK_2001_GT · Oct 19, 2006

Emay said:
I have an 07 gt and had the 3.31 as well. Didn't have the car two weeks before I bumped it to 4.10's. You will not get a bigger seat of the pants feel across the rpm range unless you bolt up a power adder.

These cars are asleep with the gramma gearing.

What RPM are you running at 60 MPH with the 4.10's?

Emay · Oct 19, 2006

I haven't paid much attention to RPM to MPH comparisons, but by chance saw today at 75mph the tach read 2700-2800

I'll pay closer attention on the way home and get the 60mph rpm range if I remember.

white-04 · Oct 19, 2006

Try 3.90s

3.90s are a good split between 3.73 and 4.10. Also, going from 3.27 to 3.90, I haven't had any mileage difference. I'm pulling 2200 rpms at 70mph in overdrive (manual car). That is not bad at all. 75mph is a little under 2400.

Very nice range on the highway, not over-revving at all.

07 GT's now have less performance

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