Actually if your are refering to fredtt he has 3:31 as his ratio. I too have an auto 05 GT, I went with the frpp 4:10's and could not be any happier with them. I say just get the 4:10's, but you also have to remeber that it is going to cost you just as much to have them installed as it is to buy them, if not more.

 

actually in the automatics from the factory they have 331 gears, the manual transmissions have the 355, he said he had an automatic trans so he does have the 331, so he would see a good amount of improvement out of the 373, i know someone who put the 410s in his 05 gt and hated them, he said he had very little 2nd gear and when he pulled out of a parking lot at normal speed he was in 3rd gear before he got straightened out in the road. so in my opinion and from what i've seen and heard in the automatic cars 373 is a good way to go, plus if you plan on a supercharger or turbo later on then 410 will be too low of a gear.

 

Like I said, I picked up .2 in the 1/4 going from stock gears to 3.73s.

 

Do the 3.90s whine that much?? How annoying is it? I've never been in a car with gear whine so I don't know what it really sounds like.

~Fred

 

I just put Ford Racing 4:10's in my '06 GT Auto (4500 miles) and absolutely love it. There's a lot of urban myths floating around about the pro's and cons with these gears. It's true that first gear is almost non-existent but someone said they hated 4:10's cuz were leaving the parking lot in 3rd gear. Hmm....that's not happening to me.

I would however recommend a tune first. you'll need it anyway to adjust the speedo. and for some of the other mods you list. Besides, you'll pay about the same if not more to get the gears and have 'em installed than the tuner. The first mod i did was the C&L cold air with the SCT tune by Brenspeed and it made a pretty remarkable increase in performance. You'll get slammed into the seat. I did the gears cuz i wanted more. Good luck.

 

I wanted to tune right after I get my CAI and Nitrous, which it next on my list after gears. Would I still see performance? Anyone add gearing and not tune?

~Fred

 

Haha, I just called my local speed shop. They told me to NOT buy motives because the are Loud and a pain in the *** to install and that they won't install them.

 

The motive 3.90s I had in my '04 GT did not whine at all. I have precision in my '05 and they whine terribly. Just put FRPP 3.73s or 4.10s in and you will be fine. You are going to need some sort of tuner to adjust for the gear change so you might as well get an intake and tuner at the same time you do your gears.

 

Fred,

I just had 3.73 FRPP gears put into my '06 with the 5spd automatic. I am very happy with their performance. See my signature for the other goodies. It WILL snap your neck & head backwards if you floor it! It is much more responsive with the 3.73's than the 3.31's.

What you have to ask yourself is how much highway driving are you going to do, and how much rpm on the highway do you want to sacrifice for lower gears?

Before I had the gear change I was taching 2000 rpm @ 70 mph. Now I tach ~2250 rpm @ 70mph. With 3.73's I still have some overdrive left to use on the highway. However, with 4.10s, you won't have any overdrive left!!

Look at your tach when you are at a highway speed you are comfortable with. If it reads 2000 now, then when you change the gears it will read 3.73/3.31 or 4.10/3.31 times the current rpm.

My case: 2000 X 3.73/3.31 = 2253rpm @ 70 mph. At 80mph it is about 2500 rpm and that is 500 rpm less than my old 1971 Buick with a 3 spd automatic and 3.08 rear end.

Had I gone 4.10's I would be taching 2477 @ 70! Yikes!!

Hope this helps.

Mike

 

I respectfully disagree. Gears multiply your torque at the wheels and it is torque that gets you going.

If you have a 300 ft-lb output with 3.31 gears, you get (theoretically) 3.31 x 300 = 993 ft-lb of torque at the wheels.

However with 3.73 gears that torque will increase to 300 X 3.73 = 1119 ft-lbs of torque; an increase of 126 ft-lbs to the wheels.

I recommend 3.73's for automatic transmissions that will see some highway driving.

If you want to race or go from stop light to stop light 4.10's or HIGHER will do the trick!

Thx,

Mike