Thoughts guys...4.09:1 gears or the FRPP Power kit for my 2020 Mustang GT PP1 manual

[JohnVallo]

You will need to change the ratio in the pcm to make it work correctly. That can be done with forscan. It's a simple procedure with a laptop and a forscan approved cable.

https://www.mustang6g.com/forums/threads/speedometer-calibration.110607/page-2#post-2875272

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[ice445]

https://www.mustang6g.com/forums/threads/speedometer-calibration.110607/page-2#post-2875272

Are there any changes needed going from the standard rear differential to a Torsen? I want to kill two birds with one stone when I do this upgrade. Also, I know the automatic need to know which gear ratio it's working with, but don't the manual cars also have what is essentially "torque tables" where the computer is always looking at wheel torque as part of the AdvanceTrak system? I can see how if you're suddenly making 10-15% more at any given time than what the ECU expects you might get unwanted behavior like power cut and such.

 

[Mikepol2]

OK that makes sense that automatics would need programming but not manuals.

The Torsen differential is completely mechanical - no programming needed.

I went from a 3.73 Torsen to a 4.09 Torsen on my manual car with zero programming needed.

 

[Superspirit]

As a retired auto tech I know for a fact the pcm uses the axle ratio in its processing formula. If it did not then why does ford supply the option to change it in the tool they send with their performance tune.

It may not affect the speedo but it will affect other things manual or auto. Even the thread referenced states that.

 

[Mikepol2]

All I can say is I've been running 4.09's for over a year with never any programming done, and if it's affected anything, I sure can't tell.

 

[Superspirit]

All I can say is I've been running 4.09's for over a year with never any programming done, and if it's affected anything, I sure can't tell.

And you may never have a problem but there is a calculation being made by the PCM that is not optimum. You will never notice the difference unless you do a lot of datalogging then flash the PCM and datalog some more. Is it worth it ? That's up to the owner. Those that have the calpac tune from Ford can change it with that. That is the route I intend to take personally.
Just so you know I'm not trying to say you've done anything wrong. I would just want that change made.

 

[MRGTX]

You will need to change the ratio in the pcm to make it work correctly. That can be done with forscan. It's a simple procedure with a laptop and a forscan approved cable.

Thanks! It looks like FORScan connectors can be purchased from our friendly neighborhood Amazon. Does it matter which one?

Will Ford be able to detect this “meddling” and void the warranty?

As a retired auto tech I know for a fact the pcm uses the axle ratio in its processing formula. If it did not then why does ford supply the option to change it in the tool they send with their performance tune.

It may not affect the speedo but it will affect other things manual or auto. Even the thread referenced states that.

And you may never have a problem but there is a calculation being made by the PCM that is not optimum. You will never notice the difference unless you do a lot of datalogging then flash the PCM and datalog some more. Is it worth it ? That's up to the owner. Those that have the calpac tune from Ford can change it with that. That is the route I intend to take personally.
Just so you know I'm not trying to say you've done anything wrong. I would just want that change made.

This insight is appreciated...it sure would be nice to know how that calculation is applied.

 

[Superspirit]

As for how it's applied is beyond my knowledge. I've read 2 books on how to tune by a prominent tuner. That said most of what I read was honestly above my high school education, but I did learn enough to tune my LT1 and the custom tune port injected 383 I built for my last camper hauler.

However none of the tuning systems I own will work on the new Ford's I own except forscan but it doesn't change the tune tables. Just diagnostics and as built. As for a cable I went with the obdlink ex it's made for forscan.

 

[Marketplaza]

I’m getting the 4.09 put in next week by my dealer. They told me that no pcm work needs done. I also asked Lund who did my tune and they told me I don’t need a extra tune as the car automatically re adjusts to the gears

 

[Dave2013M3]

I’m getting the 4.09 put in next week by my dealer. They told me that no pcm work needs done. I also asked Lund who did my tune and they told me I don’t need a extra tune as the car automatically re adjusts to the gears

Can I ask what the dealer is charging for the install?

 

[Marketplaza]

Can I ask what the dealer is charging for the install?

it’s going to cost around 1k for just the install

 

[Dave2013M3]

it’s going to cost around 1k for just the install

Yea I got quoted $700 from a non dealer. Maybe worth the extra $300 for a dealer to do it, it is a Ford part.

 

[WildHorse]

If it did not then why does ford supply the option to change it in the tool they send with their performance tune.

Because everyone on facebook/forums thinks they're smarter than Ford. Haha.

 

[Rpinaiii]

Are you all changing the whole diff or just the ring and pinion (internals)?

 

[Rpinaiii]

OK that makes sense that automatics would need programming but not manuals.

The Torsen differential is completely mechanical - no programming needed.

I went from a 3.73 Torsen to a 4.09 Torsen on my manual car with zero programming needed.

Did you buy whole diff? If so where? Just trying to find out more info thanks

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