3.15-3.73 gears
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Mach 1 Member
Joined: December 31, 2012
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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?
Mach 1 Member
Joined: August 3, 2011
Posts: 700
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From: East Haven, Connecticut
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.
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.
__________________
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.
__________________
Thread Starter
Mach 1 Member
Joined: December 31, 2012
Posts: 1,079
Likes: 0
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.
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.
__________________
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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Bullitt Member
Joined: December 11, 2012
Posts: 482
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From: N'awlins/SoCal
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.
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.
Bullitt Member
Joined: December 11, 2012
Posts: 482
Likes: 0
From: N'awlins/SoCal
That's equivalent to about 60 cases of BSN protein. 
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!
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!
Last edited by fdesalvo; Feb 25, 2013 at 06:40 PM.
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Joined: January 15, 2013
Posts: 394
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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!
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Lol I could get plenty of Test with $500! Do more for me than protein powder lol
Thread Starter
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Bullitt Member
Joined: January 15, 2013
Posts: 394
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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?
Thread Starter
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I'm going to be upgrading the suspension too, so it's definitely going to help me hook up.
Bullitt Member
Joined: December 11, 2012
Posts: 482
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From: N'awlins/SoCal
Cobra Member
Joined: September 9, 2009
Posts: 1,344
Likes: 4
From: OKC, OK
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.
Thread Starter
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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..