LL88

What is the standard differential for the GT's? what would the difference be with a 3.55 limited slip upgrade? would fuel economy be much worse with this upgrade? Thanks in advance.

aircare84

If you are talking about the 07's the standard axle is now 3.31.
06's varied by manual/auto/vert.

07GT

The standard is 3.31, optional is 3.55, both are limited slip. The option costs less than $100, I would buy it. The fuel economy would not be that much worse. Mine isn't broken in and I got 18.2mpg in town, hotrodding around. Also mine feels high geared with the 3.55's, I wouldn't want it any higher geared, many on the forum have switched to 4.11's and love it.

mustangman02232

its not worth it, save the $100 and get a set of 4.10/4.30s

vsop

I like my 3.55 gears, and its doing pretty good for me at the track so far

slow07

I have 3.31s with a manual. I get 22 mpg in town, and have gotten as high as 29mpg in highway. This all happened with "heavy" 20s, with everything else being stock. It still pulls well. It won't launch quite as well, but you won't notice much difference past 1st gear. At least I didn't, and I test drove several GTs with 3.55s.

SCCAGT

Why would the mileage rating on the window sticker give the 3.55's 25 on hwy, but only 23 on the 3.31's?
This baffles me a bit. Looking at the stickers to two cars, seemingly identical except for this difference, this is what is printed on them.
Both cars were automatics but different gear ratio.

vsop

I did not think they allowed the 3.55 option with the autos

slow07

I'm 99% sure that they are not offered on autos. That would explain why the higher gears are rated lower. From what I've seen, the manuals are rated the same mileage with both gears on the sticker.

mustangman02232

yup, becasue even though it spins faster it multiplyes torque better, hence you use less gas to accelerate at teh same speed