Change differential 3.15 on 3.55.

[any_key]

Hi. I want change differential 3.15 on 3.55.
What is the difference 3.55 on AT and MT transmission?
And what other change need done, except replacement differential?

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[5550snotamerc]

Before everyone jumps in I am going to guess that you are changing from 3.15 to 3.55?

The main thing, aside from the mechanical work, is that you will need to go into Forscan and let the computer know that you have changed it.

Apparently the computer can autodetect the ratio.

I don't know what this question means " What is the difference 3.55 on AT and MT transmission? " Are you asking what will the resulting ratios of the gears be? Do you have two cars or are you just curious?

 

[MrMike]

AT and MT used difference pinions on 15-17 models. Not sure about the future ones. You may need the matching pinion or a different driveshaft.

You'll need an entirely new diff because you have the 3.15. Just find a used Torsen and go 3.73/3.55 or buy Ford Performance M-4001-88355B.

 

[Hoofer]

I’ll add this: Changes to the diff should only be completed by a professional. If you don’t know what you’re doing, leave it alone and hire a pro to perform the work.

 

[any_key]

I have this device, and I want install him in return of the current one (3.15).

 

[junits15]

Hi. I want change differential 3.15 on 3.55.
What is the difference 3.55 on AT and MT transmission?
And what other change need done, except replacement differential?

It’s very simple, that’s about a 12% increase, so all of your gears will require 12% more engine speed for a given wheel speed.

As an example: if 3rd gear used to be 30mph at 2k rpm then after the change it will be 2250 rpm at 30 mph.

 

[any_key]

It’s very simple, that’s about a 12% increase, so all of your gears will require 12% more engine speed for a given wheel speed.

As an example: if 3rd gear used to be 30mph at 2k rpm then after the change it will be 2250 rpm at 30 mph.

Yes. How will the dynamics of the car change?

 

[GilmourD]

Yes. How will the dynamics of the car change?

Acceleration will increase, top speed will decrease.

 

[13GetThere]

Not that I would do it, but I'd like to go the other way; from 3.73 to 3.55.
Acceleration wouldn't be as good, but my cruise speed would increase. Hopefully clutch wear wouldn't be that bad.

 

[any_key]

There is a comparison table 3.15, 3.55, 3.73 - what rpm will be at speeds of 60 mph, 100 mph, 120 mph, etc.?

 

[GilmourD]

There is a comparison table 3.15, 3.55, 3.73 - what speeds will be at speeds of 60 mph, 100 mph, 120 mph, etc.?

Speeds are speeds. 60, 100, 120, or however many miles per hour the car is moving won't be any different due to gearing. The time it takes you to get to those speeds (depending on your shifting and how heavy your foot is) and the RPM the engine is spinning at (also depending on the gear your transmission is in) will be different, however.

Lemme ask this... What are you hoping to achieve? We can tell you whether that's your way forward or if you need a different solution.

 

[any_key]

Speeds are speeds. 60, 100, 120, or however many miles per hour the car is moving won't be any different due to gearing. The time it takes you to get to those speeds (depending on your shifting and how heavy your foot is) and the RPM the engine is spinning at (also depending on the gear your transmission is in) will be different, however.

Lemme ask this... What are you hoping to achieve? We can tell you whether that's your way forward or if you need a different solution.

I'm wondering how many revolutions there will be in 10th gear on the highway at 60 or 100 miles (how comfortable it will be to drive on the highway in a pair of 3.55).

And the goal is I want to improve the dynamics of the car in the city.

 

[K4fxd]

The 3.55 unit you posted a pic of is from an auto, it should be a straight swap.

You won't have to change anything in the programming of the car. The Car will auto detect that ratio.

What will change is your shift speeds. If it now shifts into 3rd at 30 it will after shift into 3rd around 27 Mph. This cannot be changed with forscan.

It is not a very big jump. I did the same swap and wish I went with 3.73.

GL

 

[Bob Lob Law]

With 3.55 A10 you will be at 2150-2200 at 80mph.

 

[80FoxCoupe]

Acceleration will increase, top speed will decrease.

On paper top speed will decrease. But in reality, top speed will increase.

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