Installing 3:31 in Torsen

[Stang-15]

I have a 2015 PP with FI and am wanting to swap gears so I can retain the Torsen. I currently have a Lund tune with a Ngauge. My question has to do with what is needed following the gear install? I have read conflicting information about what needs to be done after the install. For example, I have read that you need to have a whipppe flare tool or SCT tuner (which I have acces to) to adjust the speedo, but I have also read the BCM is self adjusting. I have read the tune needs to be modified, but I have also read it doesn't need adjusted with a manual. For those who have either swapped gears or the entire pumpkin, can you shed some light on exactly what needs to be done in regard to the speedo and tune, if anything? Thanks in advance.

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[Stang-15]

No one knows?

 

[BmacIL]

Flare tool or change the as-built data in your car.

 

[Stang-15]

Flare tool or change the as-built data in your car.

What about the tune?

 

[Ironair]

How did you get the 3.31 gears? I didn't think they were available. Did you have to buy a whole rearend out of a junkyard?

 

[ORANG50]

Have you asked Lund? That's where I'd start.

 

[rainmaker]

I changed my ring and pinion about a year ago - nothing else changed for my PP MT82 car - Lund tuned

 

[rainmaker]

I changed my ring and pinion about a year ago - nothing else changed for my PP MT82 car - Lund tuned

Might as well paint your housing while you're at it

 

[Stang-15]

How did you get the 3.31 gears? I didn't think they were available. Did you have to buy a whole rearend out of a junkyard?

You can buy them new. I found a set at LMR.

 

[kcc0521]

You don't need to change the tune. You can change the value in the BCM using Forscan. You can also use the SCT tool to change it. The information is in the link below. If you already have SCT use that.


http://www.mustang6g.com/forums/showthread.php?t=61773

https://docs.google.com/spreadsheet...l6nt9h5MGW-NWEPc04cN-ro60/edit#gid=2118936469

 

[Ironair]

I figured they had to be available somewhere since the mustang can be ordered with 3.31 gears, but what is the deal with this new super 8.8? The part number for the 3.31 says it fits the F150 and the mustang, I thought the irs rear ends were different.

 

[kcc0521]

You have to order the super 8.8 because the ring gear is bigger. TommyV and I learned this the hard way. I would order them through bear lake autonation.

 

[Ironair]

Thanks kcc0521, so are you saying there are two different part numbers? One for the older 8.8 and one for the super 8.8? I only see the FR3Z4209D, and I'm pretty sure that is for the regular 8.8, but it also says it fits 2015 mustang, so I'm confused. Sorry for getting this thread off topic, I should start a new one.

 

[EXP Jawa]

I figured they had to be available somewhere since the mustang can be ordered with 3.31 gears, but what is the deal with this new super 8.8? The part number for the 3.31 says it fits the F150 and the mustang, I thought the irs rear ends were different.

You have to order the super 8.8 because the ring gear is bigger. TommyV and I learned this the hard way. I would order them through bear lake autonation.

The Super 8.8 has a lot of differences compared to the old 8.8 gear sets. The ring bolt pattern is different, though I believe that the pitch diameter of the gear is about the same. But probably more importantly, the pinion is beefier and takes a bigger bearing. So, the gear sets do not interchange in any way.

The Ford Racing catalog I have (2016) doesn't show the 3.31:1 set, so if you wanted them, you'd have to order as a service part from a Ford dealer. As far as I can tell, the FR3Z-4209-D number should be the service part number (not the production number) for the correct gear set (2015-17 Super 8.8 3.31). https://lmr.com/item/LRS-4209-331/ford-331-gears-2015

Regarding the F-150, at least some of the '15+ trucks use a solid-axle version of the Super 8.8, which would take the same gearing as the Mustang IRS.

 

[Ironair]

Thank you EXP Jawa,
I just got done chatting with Ford Performance, and they said just what you did. I did not realize that they were putting super 8.8s in the F150, so that was what was confusing me. I thought the trucks had the regular 8.8. All makes sense now.

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