3.15-3.73 gears
 

I thought I had 3.55 gears, but come to find out, I only have 3.15s. I will be upgrading to 3.73s. What else, besides the gears, do I need to buy? I'm taking it to get installed professionally so I don't think I'll need the install kit? Just the bearing kit right?

You have an automatic? If so, that will be some serious first and second gearing.

Not sure if I'd mess with the rear if I had an auto. Seems like you burn the tires off in 1st and 2nd. A tune will wake up the car a bunch.

Keep the 3.15's. I copied and pasted this post from another board but it's a great explanation on why Ford went with those gears. Don't get hung up on the number 3.15.
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I look at it this way, the overall gear ratio is what is important. I even ran 4.30 gears for a long time and got into the 10s with them, but it was a total ***** to get the car hooked. Switched to 3.31 and lost nothing, but sure made the car easier to hook.

Consider these first gear ratios:

C4 - 2.46
4R70W - 2.84
6R80 - 4.17

Take the 4.17 and multiply it by the 3.31, you get 13.8 for an overall gear ratio in 1st. Now take that 13.8 and divide it by the first gear ratios of the other transmissions and this tells you what axle ratio would give you the equivalent with those transmissions:

C4 - 5.61
4R70W - 4.86

So, although 3.31 "sounds like" not much gear, you can see that in the end, it is quite a bit of gear with the 6R80.

We can do the same with the second gear ratios:

6R80 - 2.34
C4 - 1.46
4R70W - 1.55

That puts the 6R80/3.31 at 7.75, which is like a 4R70W with a 5.00 axle, or a C4 with a 5.31 axle.

And finally 3rd gear, where the 6R80 is 1.52*3.31=5.03, the others are 1 to 1, so 5.03 would be the equivalent axle there.


You'd all agree that an axle in the 5.00 range is a lot of gear, well, we're doing exactly the same thing with the 3.31/6R80, we just have 3 more gears to go after that.


Going the other way, a 4.10/6R80 in first gear is like having a C4 with a 6.95 gear, or a 4R70W with a 6.02 gear. You can see why hooking it is a problem.
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You're one smart cookie with that stuff... Most of that went over my head haha. My car hooks really well with the 3.15s. Rarely ever peel out. If I upgraded tires with the 3.73 gears wouldn't it hook better then?

Upgrade to 4.56 gears! Lol jk 4.10 all the way!

Lol @ Muff!

3.73s on that auto will melt your tires as you attempt to slowly accelerate from the school crosswalk and leave smoldering rubber on the children. Following Grabber's post would serve you well.

Hey grabber blue, tried to pm you but wouldn't let me. See if you can't pm me about the converter. I live not too far from circle d. My buddy has one on his G8.

Alright then.. Well that saves me $500!

That's equivalent to about 60 cases of BSN protein. :p You could pump up your legs and make a couple of Flintstone-styled cutouts in your floor pan and use those suckers to get you off the line, son!

I hate kids so I think ill like doing my tires making molten rubber give them 3rd degree burns. Maybe the parents will keep them away from playing in the roads now....4.56 here I come!

:rofl2:

Lol I could get plenty of Test with $500! Do more for me than protein powder lol

Preaching to the choir!

You a lifter too?

Anyway, I started reading on other forums of people with 3.73 gears in autos saying its the best mod they ever did.. Now I'm confused.

4.56 man! Push it to the limit! And the molten rubber on people you hate! Though idk a lot of people like the 4.10's but that might be fore the older GT's and not the 2011-2013?

I'm going to be upgrading the suspension too, so it's definitely going to help me hook up.

Natural since 07 ;)

Everybody has different opinions on gears. I have a 5.0 manual that came with 3.15s and I couldn't stand them, upgrading to 3.73s was one of the best things I ever did. I have never even sat in an Auto so I can't truly help you there, but I can promise you I wouldn't have 3.15s in my car. If traction becomes an issue then get rid of those terrible stock tires and get some real ones, I give my stock tires away, always with less than 1k miles on them.

I think I'm gonna go with the 3.73s, just not right now. It's not a super expensive mod. I've been Saving for long tubes, an now I have the money. I'm going to order them very soon along with a few suspension components. Gears, CAI, and Tune will be next..