3:15 vs 3:55

[wolf32v]

From what I have seen the 3.55's are a 1/2 second faster than a 3.15 car. Also if you want to upgrade to a lower gear like a 3.73 the 3.15 housing will not allow it. The 3.55 gear upgrade is not just a gear upgrade its also a rear end upgrade.

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[Edson8r]

What’s needed to upgrade a 3:15 rear end to a 3:55? That’s probably one of the things I forgot about when I first ordered my car. I do want to get a Torsen rear diff with the 3:55 gears since I know I won’t supercharge. My only future plans are headers, and a tune whenever that becomes available.

 

[JasonX]

I think I'm the only truly sick person who would love to see the auto with a 4.55 rear end lol.

 

[93-Oct Mayne]

Is there an advantage of the 3.15 with a supercharger over the 3.55?

Roots chargers make so much low end torque, ppl just tend to prefer the 3.15s so it's not so jumpy. Would be tougher to maintain traction off the line with a whipple and 3.55. If it's a procharger or turbos the 3.55 still good

 

[HWill]

Not sure what people are talking about with the 3.15's for FI.

I have ran 3.73 with an auto Whipple and 3.73 with a manual Procharger and it was no problem at all.
I wouldn't even get an auto with 3.15's unless you are concerned about MPG or all you can get.

 

[9secondko]

If you want a bit better gas mileage, get the 3.15

if you want more performance, get the 3.55s.

it’s a trade off.

this is the Mustang, not a civic. Get the 3.55s.

literally everything about your gas pedal application feels woken up with gears. Feels more responsive too.

 

[Q6543]

What MPH/gear do you cross in the 1/4? @HWill

Because my Calc is saying it’d be well over 8K with no real headroom for any more MPH

I currently cross around 6900 with 3.15s on a 28, and the 28 is a bias ply probably growing to almost 29

 

[Lgb0250]

I had the 3.55 in both my 19 & 22 GT’s. Thought I wouldn’t miss it since I’m not a racer so I decided to go with the 3.15 on my 24. Big mistake! The 3.55 is much more responsive in the 0-60 range. The mpg worry is ridiculous. It’s a GT, I don’t expect great mileage regardless. But, I do miss the responsiveness.

 

[Neggytive]

3.55 with the standard issue differential or 3.55 Torsen for $1000?

IMHO if the car has a 10 speed you can use the ratios in the transmission to overcome the perceived lack of get up and go of the 3.15:1 gear set.

The car I ordered and cancelled due to too long a lead time to get it was going to get the 3.55:1 Torsen rear end but I was also planning on doing a Ford Performance (Whipple) Supercharger.

There is a reason the stick cars have the lower gears, and that is because the limited number of gears in the box limits the available effective gear ratios ( transmission gears, rear end gears, tire size)

If I were going to be racing the car or putting a power adder on it I'd absolutely want the Torsen differental

The 3.55 gears from Ford Performance or Richmond are not big bucks, you are all in for about $500 for parts/fluid plus labor and a reprogramming of the speedometer and the transmission shift points.... You can buy a complete center section with 3..55 gears for about $1100... drop out the existing one bolt in the 3:55's

There are also 3.73's and 4.10's gear sets available from Ford Performance and Richmond Gear

There is also the option of buying a LKQ/Used center section from a wrecked car, but again you will need some computer time

 

[jamespmoran]

I have a GT Premium Convertible. I went we the 3.55 because of the extra weight. Glad I did.

 

[Rocket Man]

What MPH/gear do you cross in the 1/4? @HWill

Because my Calc is saying it’d be well over 8K with no real headroom for any more MPH

I currently cross around 6900 with 3.15s on a 28, and the 28 is a bias ply probably growing to almost 29

In what gear?

 

[asc709]

The n/a 5.0 will feel weaker at low RPMs in 1st with the 3.15. At least it did to me when I first drove one. I had 3.73 on my old manual car and it felt like it needed more. My new car has the 3.15 rear and an A10 with the Whipple. I feel no lack of low end in any gear. 1st gear is pretty much useless and 2nd is tricky. As I get more time with it, I’ll see how she feels.

 

[Q6543]

In what gear?

6th… you do not want the 10R80 shifting into 7th WOT with decent HP… they don’t take that for long.

 

[Farmer Fran]

My math says with 265/35-20 tires at 7500rpm

3.55s
1 - 4.70 = 36.5
2 - 2.99 = 57.4
3 - 2.15 = 79.8
4 - 1.80 = 95.4
5 - 1.52 = 112.9
6 - 1.28 = 134.1
7 - 1.00 = 171.7

3.15
1 - 4.70 = 41.2
2 - 2.99 = 64.7
3 - 2.15 = 90.0
4 - 1.80 = 107.5
5 - 1.52 = 127.3
6 - 1.28 = 151.1
7 - 1.00 = 193.5

 

[Rocket Man]

what gear do people normally dyno in?
I thought you wanted 1:1 for that. Not for drag racing evidently.

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